I don’t know if you’ve checked, but I did noticed some oil in the manifold. You might have to replace the PCV valve. Happened to my friends car. During stops, it would hesitate and die sometime. Change the PCV valve and fixed it.
These engines don't have a replaceable valve... They do have a hose that rots into black powder that connects airbox to metered port on valve cover. I have zero idea what they made em out of...
I am a ASE certified diagnostic technician who has decades of experience. This is a running list of things that popped into my head of what possible causes might be... Reminds me of the 5 cyl they put in the Colorado and Trail Blazer, Those intake plenums love to crack and leak. A way to help determine if there is an intake leak is to hook up the scanner and observe the short term trim data and see if is trending to a negative trim, also observe the long term data to see if it is also in negative trim. Another observation is O2S1 trending lean. [hanging closer to 200mv] A smoke machine can be helpful in identifying intake leaks, feed the brake booster line with the smoke. The valve cover bolts are shoulder bolts and torque is not really important. They tighten to the shoulder and dictate max pressure on the seals, you just want to be sure they can't vibrate loose and of course don't snap them off into the head when tightening, use common sense when tightening. Confirm plugs aren't oil fouled from previous valve cover gasket well seal leaks. [you should have done that while the cover was off and just went ahead and put new plugs in as well. A/C Delco likely platinum. Platinum are usually good for a 100k] Clean the mass air flow [MAF] if it has one and if it does the scanner should reveal between 5-6gpm at an idle for that size motor. Confirm the actual gpm spec, it is also a high suspect for rough idle. O2S1 and trims can also reveal leaking injector(s) via a rich reading or positive trim. Check the misfire count data if available [not all models have that feature] to help identify random misfire or cyl specific misfire, typically if the misfire exceed a threshold it will set and code and the MIL light on. If misfire is more on a specific cyl, then swap the coil pack with another cyl and see if the misfires move with the coil pack to determine if you have a faulty coil pack. [COP] Check the motor mounts, hydraulic ones live to leak out the oil and then transmit engine vibration the chassis giving a feeling of rough idle. Most engines have a small amount of random cyl misfires or aren't perfectly balanced although a 6 cyl crank is automatically naturally balanced.
I'm not a certified "anything" automotive-wise, just a guy who's done most of the routine (I.E., "easy) work on my own vehicles for the last 50-ish years. But I really enjoy reading posts from guys like you, who know the business. A "pro-" in almost any profession with run circles around even the highest-ranked amateur in the same line of work. Thanks for posting!
@@1RoadGaragehey… I’m wondering why you did not change the spark plugs? If oil is down in those holes you need to pull and replace the plugs. Also put your stock coils back. I have a 2008 trailblazer with almost 190k and the engine runs perfect. I’m also a mechanic. With that oil in the intake I would run a catch can. You probably have a little low by that may be fouling some plugs. The hose in the center of the intake from rope to bottom. Cut that and plumb in a catch can
If ur thinking of a vacuum leak maybe use a smoke machine I know that kinda a special tool but maybe have a buddy or someone and smoke the intake system and if it is leaking due to looping idle. Maybe use a scan tool and also look at fuel trims and see if it running rich or lean? Just shooting a idea out there
Smoke machines are easy to make. There are multiple TH-cam videos showing how to make them. There is no excuse for not diagnosing a problem … just throwing parts at it.
The ticking could be the timing belt tensioner. And if the chain is off a bit that could be the rough idle. They are known to stretch. Replaced mine this last summer
If you suspect a manifold gasket leak, before you dismantle, with engine idling, spray the gasket areas with carb cleaner. If the engine slows down, you have a leak. When you have a weird sound, you can isolate it well with a stethoscope with a long narrow tube on it, made for that purpose. It's low tech but you can narrow down where the sound is coming from. As for the AC Delco alternator, I bought a NEW one for my '03, ZR2, not rebuilt, from Rock Auto and got a great deal on it. The original lasted 125k. The new AC Delco alt, started making bearing noise after about 7k miles. I'm still running it, but yes, Delco junk. But was able to isolate the noise to the alt with the stethoscope probe.
As far as isolating noise sources, you can use a longish piece of wood like an old broken broom handle placed on the suspected noise cause and placed near the ear. The high (relative to air) density of the stick will aid in pinpointing the source. A trick my dad taught me for finding bad bearings/bushings. Hope that helps someone.
First time viewer, aircraft mechanic and I was raised on a farm and worked on tractors and vehicles my whole life. I would check the fuel pressure at your fuel line you disconnected, a weak fuel pump can cause idle issues and stalling, stumbling, weak aceleration, etc. like the things that you mentioned. Fuel pump is probably inside the fuel tank on the tank quantity sending unit.
@@Failure_Is_An_Option - I'm 68 years old now, I worked on quite a number of different types of aircraft for over 30 years including military and civilian aircraft (General Dynamics, Boeing and Rockwell, etc) plus I worked on my own cars and pickups until in recent years when they went super computerized. When you can walk the walk and match me or beat me then you can talk but until then weak talk like name calling is all you have.
Over the years I have replaced 10-12 intake manifolds on the 4.2 and 3.7 due to cracks forming in the seam across the back of the intake. They suck in un-metered air and cause roughness. Can usually see it in the fuel trims. I made a couple plates to bolt on to seal off the manifold and use a smoke machine to check for leaks,
Though I’ve never played with the inline engines.I’ve had similar issues with a caddy 3.6 and a few 4.8,5.3,6.0’s with a purge valve not sealing or operating properly. The old test was to unhook it take off and see if you blow thru it. If you could it would be labeled as bad. The fancy way is with a scanner and watch fuel tank pressure as you use a scanner to open and close the valve. Best of luck on finding the issue and always enjoy your videos! Cheers!
@@1RoadGarage While the scanner is out, check command / actual pintle positions on the IAC and EGR. The ECM will give a little leeway of 10% difference before throwing a DTC. And if you've ever used a scanner to manually change EGR and IAC, that 20% step makes a big difference in idle quality. I was checking out a friend's ailing vehicle, on my snap-on and was testing both and she said "there's it's running bad now what is it?" and I said "nope, that was me". There could also be a relearn due on the IAC or throttle (since you cleaned it)
Recently had a pvc valve replaced and you blow through it both ways. That proved it was bad. It looked very rough. Lots of carbon build up on it. As far a getting a smoother running motor, it didn't help. Back to the question board hunt.
On my Izusu asscender same car, fuel pressure. Wasn’t the fuel pump it was the connection to the relay under the relay box. Fixed the connection ran great. Best of luck
Don't worry about the critics, if it doesn't fix it you still got a video showing how to do a task on this truck. Helps some who's wants to know how to do this task
There's always armchair mechanics that comment when a repair video comes out. They probably haven't ever turned a wrench, they did their training on Facebook.
Intake leaks cant lean your engine out and tear an engine up. Ive had valve cover gaskets leak and KILL my alternator a few times in my time. Good video brother.
Detonation caused by a lean condition can kill an engine. Very slight detonation on a stockist low compression engine, it can run for a long time. A higher compression engine it will kill alot faster. Unless it's a to church on Sunday and never sees 2500 rpms or above.
Great tutorial on how to change the intake and valve cover gaskets, not a total loss! You resealed a problem area and now oil will not fill up the sparkplug wells. You will find the problem, Jimmy. You got this!
Sir, you seem like the perfect person to speak on an experience I had with engine noise. I had a loud engine tick that cane suddenly, and I was 100% sure it was a rod bearing because it was coming from the bottom and was much louder under the van whether the hood was open or shut. I bought new bearings, sandpapers, and other stuff. After pulling the pan, I didn't find anything loose. On a hail mary, I opened the top of the engine because these vans are known for ticking lifters, so I replaced any that i felt were too loose. Problem solved. Relief set in x 1000. But, the wierd thing is how loud the top-end tick was u derneath the van. Anyone hearing that wouldn't have said it was a lifter unless they had that exact problem before.
As you saw the intake valves were dirty. This is a problem when they went to direct injection. In the past, fuel was sprayed behind the valves. This kept them clean by using the fuel as a solvent. Gm sells a solvent and a brush that you remove the intake manifold and spray/scrub the intake valves. Depending on how you drive this vehicle, this should last many miles. But I’ve seen this last as little as 6000 miles. This is dependent on your driving conditions. Good vid and at least you got that noise fixed.
Yeah once you start getting excessive blow-by and TPS codes and variable valve Solenoid codes the motors done bad design all around The electrical problems on these motors are too many to list
Your alternator "knock" was probably being picked up by the knock sensor, causing the ecu to adjust ignition timing. The intake gasket may or may not have been faulty also.
That flattening is called compression set, all elastomeric materials will take a set after prolonged compression an heat adds to this issue, elastomers are really highly viscous liquids, its just a matter of time before this happens
My 2002 2500hd with the 6.0 wouldn't stay running when cold once it was warm it did fine. I replaced the factory intake manifold gasket with Felpro. Been working flawlessly! My understanding is that GM factory intakes gaskets was junk and they changed the material later. They shrink when they are cold, once warm air flows the expand back to where need to be. I think i read to use flepro.
Check the valve clearances. differences in valve lash greatly affects valve overlap. If I pull a valve cover for any reason, I do that, just to look for obvious problems. Injection systems are very accurate delivering the same dose of fuel to each cylinder. It's extremely important, that the volumetric efficiency of each cylinder is exactly the same. If some cylinders are rich, and others lean, the O2 sensor will pick a "happy medium" causing a power imbalance, and, higher emission figures. you can get some clues, by pulling and reading the sparkplugs. another possible vacuum leak may be the vacuum brake booster, or, the heater vent controls. Remove those lines from the manifold, plug them, and see if the engine runs any better. I don't understand what you mean by "never touch your factory intake manifold gaskets".
Trailblazer and Envoy intake manifold, bolts, back out overtime with hot and cold cycles. I chased a intake leak forever until I found a couple of the bolts in the back were loose.also make sure you clean the throttlebody. These trucks are very sensitive to that.
These engines are known for pumping the cylinder head full of oil(prolly bc gm was scared of grenading engines with the new vvt/dohc setup) and those spark plug gaskets will seep oil especially on the inner spark plugs(cyl 3,4) and coils causing intermittent misfires that often go unnoticed for very long times.
First thing I do when diagnosing an engine noise is release tension on the accessories belt and run the motor for a few seconds. If the sound goes away, it’s an accessory. Troubleshoot alternator, power steering, AC clutch and water pump as necessary.
A lot of speculation as to your issue. My recommendation would be to buy a scanner that has 'mode 6' readability. I personally use the Blue Driver. It has lead me to the source of multiple small issues (including random rough idle). Firing the parts cannon at something is great for learning. And more power to you in that. But, it can get expensive. And it doesnt jave to be. Keep on keeping on.
Mass air flow meter it is possible to clean them with electric contact cleaner spray on heated wire with it removed form car put in plastic bag so the cleaner doesn’t evaporate and give it a good spray . Then let air dry 👍
What you say is true but that takes an experienced technician to interpret, and the right equipment. And it may cause you to suspect a vacuum leak but NOT tell you where. There are several other ways to find vacuum leaks that require less technical knowledge and will take you to the source.
Maybe the mass air flow sensor? Similar issue on older Chevy's I have worked on in the past and it was the MAF. Going to do my valve cover gasket soon as well for the same reason of oil in some of the spark plug holes.
The new gaskets and grommets look like flourosilicone (blue) vs most likely silicone. The flourosilicone is five times as expensive but has superior resistance to petroleum products and oxidation over time and should have been used by GM from the get go.
I had the tensioner pulley go out and snapped the belt. Luckily the tow truck driver diagnosed the cause and he drove me to the autoparts store - and then he called his buddy to install it for me (cash). Wow - I got saved from being stranded on the weekend.
Recommend checking coil packs (ohm and Meg), fuel filter, check readings for MAP, MAF, and TPS, look for cracked vacuum lines. These are some items that I have chased in the past. Don't just throw parts at it, try to verify bad parts. Great work on finding the bad bearing in the alternator. I've had that one before too, lol.
THESE IN - LINE 6 ‘S ARE VERY TEMPERAMENTAL, FOR THIS REASON I ONLY USE DELCO / DELPHI REPLACEMENT PARTS , I HAVE 230 K ON AN 02 TRAILBLAZER IT STILL HAS THE ORIGINAL ENGINE , ALTERNATOR NO BEARING NOISES !!!
The engine mounts can cause a vibration or also that one may feel as a loping at idle. I had to change my 2004 Envoy engine mounts and it made a big difference. The throttle body should be cleaned gently and no cleaner run down into the electronics that operate the throttle. The throttle plate is not supposed to be moved by hand either.
I've own a 2004 Trailblazer for 15 years. I bought it with 65k miles. It has 191k miles now and still has 4 stock coils. It run great and has never fail an emission test. People trip me out when they change all 6 coils when the engine start to run funny. When the coils are bad. You will know it because you will get a skip.
7:09.. For 65K, that engine is clean! I had a 2007 Mustang GT, it would stall out, glitch, and throw codes for cam position and crank position codes.. One day I went to start it and the brand new battery was completly flat. That's when I realized it was a failing alternator the whole time.
Smoke the intake and valve cover etc. This is a very good way too either find a leak or eliminate them from the diagnosis. You also could have something affecting your fuel system, you really need a scan tool to check that , and many other things. You don't have to have a cel for something to be wrong. Hope this helps.
I was an auto mechanic in the 80s for 8 years. I thought those cars were a pain to work on with all the emissions controls and the start of electronics controlling everything. Hats off to the auto mechanics today you really earn your pay, the way these cars are built today.
Had a rough idle on my 09 impala. Needed work on the tps (throttle position sensor) and I also cleaned the idle air intake and put in all new air filter. This solved the issue, but it’s also worth noting that I did put in a new injector wiring harness. This was at 235,000 and the engine previously was running on all factory parts (replaced the serpentine belt at 240k and spark plugs and plug wires a little before 235k). I reused the original intake manifold gaskets and it’s been running like a top aside from a small evap leak that’s probably a gasket that I should’ve replaced when I did the wiring harness
Replace your vvt solenoid, and ohm your coil packs. Even new delphis have been faulty. The problem should go away. I chased a missfire on my 4.2 for two years. Injectors, plugs, purge valves, regulators, fuel filters,pump, in the end it ended up being a faulty coil pack, and a bad vvt solenoid. It ran perfect after that. Had gobbs of power and gas mileage was great. Unfortunately the 4l60 left the building shortly after.
$4K for a Reman transmission - and I'm hoping the engine will last another 250,000. hahaha. I put an external OEM Magnefine inline filter on the transmission - runs way better now.
Hi Jimmy Concerning the ruff idle, sometimes running the engine at lower rpm at idle can cause a ruff idle and intermittent shut off because the engine is not getting the right mix of air and fuel, try turning the idle up. E.G. If idling at 500 rpm try turning it up to 600 rpm and so on. If that doesn't work try a adjusting the air to fuel mix to see if it is that was the cause of the ruff idle, if all is controlled by a ecu then a retune may be needed of the ecu settings. If that does not fix it then the wiring loom needs to be looked at because the ecu and the wiring loom especially the connectors to the sensors are a weak point in the electronic fuel control system.
When I had similar idle issues I cleaned the throttle body and that solved it. I only had 50k miles on it but there was already carbon buildup on the throttle body.
Check into your downstream O2 readings. Compare it to where it should be... My father in law changed the transmission out of his 06 trailblazer I6 due to a rough idle and a "slip" condition. Turns out his catalytic converter was quite plugged, but plugged enough to set a code. Weird I know but changing out the cat fixed his problem... Don't know if that helps but it's worth looking into.
I had this problem as well I diagnosed by drilling a 1/8 inch hole before the cat and measuring the exhaust pressure using a vacuum gauge (very cheap at harbor freight) Mine was also rattling, almost as though a chunk of material broke off... I was throwing all kinds of codes too it was a diagnostic nightmare!
90 chevy truck butterfly in exhaust was rattling once in a while , which sensors picked up as engine knock adjusting fuel causing rough engine running, swapped about a hundred things before one thing standing on passenger side it rattled and engine acted up.
The rough ideal if the battery was disconnected probably the vehicle is just having a hard time relearning its map (An engine map is essentially a table of data that is used to tell the engine what to do in certain situations.)
I used cheap Rock Auto Coils, Injectors and used alternators off Ebay to keep my 408,000 mile NY 05 Colorado on the road. I used Mobile 1 since brand new and changed oil every 6000. All the rough running I've ever experienced is due to harness corrosion especially to coils and injectors. If you don't tighten your coils enough. You will get oil in the plug holes.
That stumbling can be tough to diagnose, especially when no engine light comes on. There are a couple things you can check if you have an OBDII reader. Most obd readers give mode$06 data, which has test results for the monitored systems, there could be logged misfires on a particular cylinder. And then checking the total fuel trim (long-term fuel trim + short-term fuel trim. Or ltft stft.) Most manufacturers won't set a fuel trim fault until the total is +20% or -20%. Fuel trim is a command, i.e., sensors telling the computer add or subtract fuel. That rattle noise at the beginning of the video souded like a water pump or fan clutch failed, and I've experienced a faulty fan clutch causing idle concerns on many vehicles.
There's still things to check, all vacuum hoses and fittings, smoke test if you can, check short term fuel trims with a scan tool, it could be the isc.
Hi Jimmy, out of curiosity. Have you replaced the engine coolant temp sensor by chance? The 4.2 relies heavily on every one of its sensors to run correctly, and a flaky sensor can definitely cause it. If possible, I would do a fuel pressure test to be on the safe side. The factory rated pressure specification is 50-57 PSI, anything less is typically a fuel pump. If the fuel pump needs to be replaced, stick to BOSCH (they provide the OEM fuel pumps for the 4.2, and 5.3 Envoy/TB.) I would give the MAP sensor a good cleaning (or replace it, its a relatively cheap part). Since the 4.2 was never equipped with a PCV system, all the oil/blow-by just gets sent back through hence why the intake manifold had that gunk around the ports. The MAP sensor is located at the top of the manifold next to the throttle body. The rough idle/stalling at a stop were usually linked to the throttle body being dirty, but since you've cleaned it you MAY need to do a relearn (if you haven't). The procedure for the 4.2 is; Disconnect the negative cable Leave battery disconnected for 30-40 minutes Turn key to ON, do not start the engine or touch the gas pedal. You may/may not hear the TB actuating during this time. After leaving the key to the ON position for 5 minutes, do not turn the key to the off position, instead start her up and let her idle for 10-15 minutes. Drive around to get it to operating temp, and see if that makes a difference. Otherwise, I would suggest getting a test done on the fuel injectors.
I was about to suggest the same thing I had many cases where MAF/MAP gets wet from oil/moisture and it trows the drivebility of the car way off - sends wrong data to the ECU and the car starts misfiring, dying and all sort of wierd stuff
I had a similar issue with my RSX (acura integra), turned out to be a vacuum leak! -they are way more sneaky than you'd think, other things i would check -upstream 02 sensor, catalyst & finally (not very likely and I have no idea how you would confirm but.. the transmission could potentially be loading the wheels more than expected in first gear?)@@1RoadGarage edit: also, is there a chance you just aren't used to the inline? haha -you gotta remember secondary balance is not what they're about, top end power is what inlines are for!
Ruff idle is usually a cam position sensor and or crank position sensor and your around mileage they will need changed give or take. Also when the catalytic converter starts plugging up it will cause weird ruff idle and other symptoms that are not consistent at all.
A fuel injector causes misfires too, usually gets ignored, a noid light set helps. If it is actually picking up a misfire on a particular cylinder, you can swap injectors around to duplicate a misfire on a different cylinder. Check fuel pump pressure, low fuel pressure can cause a boggy idle and a dead spot on acceleration. If there isn't a misfire being picked up, have the exhaust backpressure tested, that can cause an engine to be sluggish at low RPM
Also check for a clogged cat. I used "cataclean" recently on my 2007 hummer with 3.7. It runs better and better fuel economy. I also used it on my 04 6.0 powerstroke and fuel millage is better. Clogged cats can cause rough idle.
You need a good scanner to check your computer for error codes. After what you have done to that car i would be checking the fuel pressure. How long is it since you changed the fuel filter?
Did all this on my '04 Envoy about 4 years ago at 260K miles, plus changing the fuel injectors. She's got 296K on her now. I notice you didn't show getting to that rear-most intake bolt. What a PITA. By the way, I thought mine was idling rough...change your motor mounts. Not that hard. Makes a world of difference.
Bro. Not to be negative. But 65k on the third alternator and having issues with the engine, Maybe the problem is the oem parts. Was a good video. Get a computer so u can check different perimeters like ur fuel trims and o2 sensors, that kinda diag information is critical when dealing with rough running engines
On the alternator. Pull off that back plastic piece if it's easy to take off. You should be able to see that back bearing cover. Make sure the cover is there. It's often a piece of sheet metal pressed into place. Sometimes they forget and that'll cause dirt to be sucked into the bearing. Then it'll go bad and make noise. I always check.
Sounds like Idle air solenoid, usually just cleaning them works, but cheap to replace. Also check the temp sensor reading with scan tool (sensor in intake)
Does this car have a gas tank vapor absorber? I had a similar story, I used smoke to find leaks, they were there, but they only affected the corrections that I looked through the ELM scanner. The main reason turned out to be a stuck adsorber valve, which did not close by about 5-10%. And also, everything is fine, but the idle is not smooth. Replacing the valve solved the issue.
Haha, your thumbnail caught my attention, I have the 2.9 version of the Vortec inline with the same manifold and everything really, I actually have a rough idle on my truck, it's kinda on and off but not nuts, maybe I'll take a look at these gaskets now, could be the culprit, cheers!
Some of these have a metal intake alternative. My Buick has a later style metal alternative I’ll be switching to when I go to do my lower intake gaskets next weekend. Got the adapter plate, & changing the lower intake elbow orings or just new elbows cuz it already has the metal ones. Try some fuel cleaner next on it, & see if that helps.
Fuel injectors clean and how old is the fuel filter? I'd double check for vacuum leaks. I used to just get a water bottle and put a small hole on the top and squirted over the engine. Definitely do the basics first like these. When I an auto tech, a lot of idle issues were due to maintenance like injector cleaning.
I would suggest maybe changing the engine and transmission mounts. It's possible that the rubber in one of them is ripped and causing a slight shudder.
I had the alternator for my 97 Olds 88 go out with bad bearings. It was an upgraded Mechman alternator and the bearing towards the rear totally blew apart and was wobbling around. Thankfully I could limp home and had power if I let the engine idle but as soon as I gave it gas it would moan really bad and drop the voltage.
Is your fuel filter located inside the tank with fuel pump or is it outside the tank, my Pontiac torrent has that idling problem too and my fuel filter is inside the tank
Best tool for finding that tick is a mechanics stethoscope. Best tool for finding a leak is a can of carb cleaner. Just spray around any potential vac leak and listen for stalling.
While we are throwing parts at it, replace the knock sensor and crank position sensor. Both located next to each other on the driver's side engine block down low. Access from driver/front wheel well (Envoy on jack stand) and underneath. I had to replace the CPS on my 8.1L Burb because it was stalling out intermittently while I was driving. Age could be getting to motor and tranny mounts, as well. Also, a long extension from a part to the ear is good for finding sounds, just be real careful on a running engine not to get into the fan or belts.
Gunk on throttle body plate. Give it a good cleaning and see if it changes things. My 5.3L 2013 Avalanche's throttle plate was pretty caked. A toothbrush with some intake cleaner smoothed things out quite a bit. Still not perfect but does WAY less throttle wobbling.
Does it have fuel filter that is not in the tank? If so I would change the fuel filter. What brand of spark plugs are in it? I would put the exact plug in that it left the factory with. Should tell you in the owners manual. So it was doing this with the old coils and you replaced the old coils with new coils and it still does it? Do you get a random cylinder mis fire code or are you getting a specific cyclinder misfire code? What is the live stream data saying?
you get signs what is the problem. noise from alternator refer that camshaft not balance, it's mean that becasue camshaft spins not in center then alternator will have damage to alternator bearing.-------------------------------------------------------------------------------------------------- conclusion : 1) one or more of engine cylinder or valve had leak, you can easy check that with ODB (check negative pressue on idle), because of that the camshaft will not be balance and you will get also oil leak. ----------------------------------- i think it not worth to fix.
I don’t know if you’ve checked, but I did noticed some oil in the manifold. You might have to replace the PCV valve. Happened to my friends car. During stops, it would hesitate and die sometime. Change the PCV valve and fixed it.
These engines don't have a PCV valve, just a hose.
@@staceyward777True, but if the orifice is plugged, it's the same thing as a bad pcv valve.
Generally clean the ports and manifold. Especially if you a PCV and EGR.
@@anonemoose6622 My 4.2 with 290K on it isn't plugged. On a motor with less than 70K, that's probably not the problem.
These engines don't have a replaceable valve... They do have a hose that rots into black powder that connects airbox to metered port on valve cover. I have zero idea what they made em out of...
I am a ASE certified diagnostic technician who has decades of experience. This is a running list of things that popped into my head of what possible causes might be...
Reminds me of the 5 cyl they put in the Colorado and Trail Blazer, Those intake plenums love to crack and leak. A way to help determine if there is an intake leak is to hook up the scanner and observe the short term trim data and see if is trending to a negative trim, also observe the long term data to see if it is also in negative trim. Another observation is O2S1 trending lean. [hanging closer to 200mv] A smoke machine can be helpful in identifying intake leaks, feed the brake booster line with the smoke.
The valve cover bolts are shoulder bolts and torque is not really important. They tighten to the shoulder and dictate max pressure on the seals, you just want to be sure they can't vibrate loose and of course don't snap them off into the head when tightening, use common sense when tightening.
Confirm plugs aren't oil fouled from previous valve cover gasket well seal leaks. [you should have done that while the cover was off and just went ahead and put new plugs in as well. A/C Delco likely platinum. Platinum are usually good for a 100k]
Clean the mass air flow [MAF] if it has one and if it does the scanner should reveal between 5-6gpm at an idle for that size motor. Confirm the actual gpm spec, it is also a high suspect for rough idle.
O2S1 and trims can also reveal leaking injector(s) via a rich reading or positive trim. Check the misfire count data if available [not all models have that feature] to help identify random misfire or cyl specific misfire, typically if the misfire exceed a threshold it will set and code and the MIL light on. If misfire is more on a specific cyl, then swap the coil pack with another cyl and see if the misfires move with the coil pack to determine if you have a faulty coil pack. [COP]
Check the motor mounts, hydraulic ones live to leak out the oil and then transmit engine vibration the chassis giving a feeling of rough idle. Most engines have a small amount of random cyl misfires or aren't perfectly balanced although a 6 cyl crank is automatically naturally balanced.
I'm not a certified "anything" automotive-wise, just a guy who's done most of the routine (I.E., "easy) work on my own vehicles for the last 50-ish years. But I really enjoy reading posts from guys like you, who know the business. A "pro-" in almost any profession with run circles around even the highest-ranked amateur in the same line of work. Thanks for posting!
Thank you for all of that information! Will be looking into it.
@@1RoadGaragehey… I’m wondering why you did not change the spark plugs? If oil is down in those holes you need to pull and replace the plugs. Also put your stock coils back. I have a 2008 trailblazer with almost 190k and the engine runs perfect. I’m also a mechanic.
With that oil in the intake I would run a catch can. You probably have a little low by that may be fouling some plugs. The hose in the center of the intake from rope to bottom. Cut that and plumb in a catch can
If ur thinking of a vacuum leak maybe use a smoke machine I know that kinda a special tool but maybe have a buddy or someone and smoke the intake system and if it is leaking due to looping idle. Maybe use a scan tool and also look at fuel trims and see if it running rich or lean? Just shooting a idea out there
100% he had problem with intake leak, one or more of engine cilinder had pressure leak.
Used to spray carb spray at a suspected intake leak, if it caused a stumble, you knew it was leaking.
Spray diesel start around the gasket, you'll know, when it revs up
@@lewisbolman7862ether that or carb spray 😂
Smoke machines are easy to make. There are multiple TH-cam videos showing how to make them. There is no excuse for not diagnosing a problem … just throwing parts at it.
The ticking could be the timing belt tensioner. And if the chain is off a bit that could be the rough idle. They are known to stretch. Replaced mine this last summer
If you suspect a manifold gasket leak, before you dismantle, with engine idling, spray the gasket areas with carb cleaner. If the engine slows down, you have a leak. When you have a weird sound, you can isolate it well with a stethoscope with a long narrow tube on it, made for that purpose. It's low tech but you can narrow down where the sound is coming from.
As for the AC Delco alternator, I bought a NEW one for my '03, ZR2, not rebuilt, from Rock Auto and got a great deal on it. The original lasted 125k. The new AC Delco alt, started making bearing noise after about 7k miles. I'm still running it, but yes, Delco junk. But was able to isolate the noise to the alt with the stethoscope probe.
crazy how an entire alternator can be ruined by a crappy bearing.
@@1RoadGarageYup. Got a brand new Delco idler wheel once that the bearing was bad from the box.
I use brake cleaner for finding leaks. Although it's bad for plastic
As far as isolating noise sources, you can use a longish piece of wood like an old broken broom handle placed on the suspected noise cause and placed near the ear. The high (relative to air) density of the stick will aid in pinpointing the source. A trick my dad taught me for finding bad bearings/bushings. Hope that helps someone.
@@tenflat2009I've seen a large, long screwdriver used also.
First time viewer, aircraft mechanic and I was raised on a farm and worked on tractors and vehicles my whole life. I would check the fuel pressure at your fuel line you disconnected, a weak fuel pump can cause idle issues and stalling, stumbling, weak aceleration, etc. like the things that you mentioned. Fuel pump is probably inside the fuel tank on the tank quantity sending unit.
So can a vacuum leak weak battery clogged oil pump lots of stuff
@@itz_real_notch9813 yes, but there was no pressure in the fuel line he disconnected. Though maybe he depressurized the system off-camera.
Stumbling on acceleration is a good way to describe what happens when fuel pumps begin to fail.
Checking the pressure is fairly easy
Sure you didn't build the shuttle and international space station too? What a clown.
@@Failure_Is_An_Option - I'm 68 years old now, I worked on quite a number of different types of aircraft for over 30 years including military and civilian aircraft (General Dynamics, Boeing and Rockwell, etc) plus I worked on my own cars and pickups until in recent years when they went super computerized. When you can walk the walk and match me or beat me then you can talk but until then weak talk like name calling is all you have.
Over the years I have replaced 10-12 intake manifolds on the 4.2 and 3.7 due to cracks forming in the seam across the back of the intake. They suck in un-metered air and cause roughness. Can usually see it in the fuel trims. I made a couple plates to bolt on to seal off the manifold and use a smoke machine to check for leaks,
I had similar issues with a 6.0l. I ended up replacing the throttle body. But the issue was the throttle position sensor. Good luck.
yes the throttle body valve HAS to be cleaned regularly. I need to do mine again - once a year. thanks
Though I’ve never played with the inline engines.I’ve had similar issues with a caddy 3.6 and a few 4.8,5.3,6.0’s with a purge valve not sealing or operating properly. The old test was to unhook it take off and see if you blow thru it. If you could it would be labeled as bad. The fancy way is with a scanner and watch fuel tank pressure as you use a scanner to open and close the valve.
Best of luck on finding the issue and always enjoy your videos!
Cheers!
Thanks!
@@1RoadGarage While the scanner is out, check command / actual pintle positions on the IAC and EGR. The ECM will give a little leeway of 10% difference before throwing a DTC. And if you've ever used a scanner to manually change EGR and IAC, that 20% step makes a big difference in idle quality. I was checking out a friend's ailing vehicle, on my snap-on and was testing both and she said "there's it's running bad now what is it?" and I said "nope, that was me".
There could also be a relearn due on the IAC or throttle (since you cleaned it)
Recently had a pvc valve replaced and you blow through it both ways. That proved it was bad. It looked very rough. Lots of carbon build up on it. As far a getting a smoother running motor, it didn't help. Back to the question board hunt.
On my Izusu asscender same car, fuel pressure. Wasn’t the fuel pump it was the connection to the relay under the relay box. Fixed the connection ran great. Best of luck
Don't worry about the critics, if it doesn't fix it you still got a video showing how to do a task on this truck. Helps some who's wants to know how to do this task
There's always armchair mechanics that comment when a repair video comes out. They probably haven't ever turned a wrench, they did their training on Facebook.
I saw no critic posts. Everyone was positive and liking his video.
My rough idle was do to carbon build up on the throttle body blade
Depending on your scan tool, look at mode 6 data to see misfire data. There are videos about it.
Intake leaks cant lean your engine out and tear an engine up. Ive had valve cover gaskets leak and KILL my alternator a few times in my time. Good video brother.
The valve cover leaking oil killed the alternator.
Detonation caused by a lean condition can kill an engine. Very slight detonation on a stockist low compression engine, it can run for a long time. A higher compression engine it will kill alot faster. Unless it's a to church on Sunday and never sees 2500 rpms or above.
Great tutorial on how to change the intake and valve cover gaskets, not a total loss! You resealed a problem area and now oil will not fill up the sparkplug wells.
You will find the problem, Jimmy. You got this!
Sir, you seem like the perfect person to speak on an experience I had with engine noise. I had a loud engine tick that cane suddenly, and I was 100% sure it was a rod bearing because it was coming from the bottom and was much louder under the van whether the hood was open or shut.
I bought new bearings, sandpapers, and other stuff. After pulling the pan, I didn't find anything loose.
On a hail mary, I opened the top of the engine because these vans are known for ticking lifters, so I replaced any that i felt were too loose.
Problem solved. Relief set in x 1000.
But, the wierd thing is how loud the top-end tick was u derneath the van.
Anyone hearing that wouldn't have said it was a lifter unless they had that exact problem before.
As you saw the intake valves were dirty. This is a problem when they went to direct injection. In the past, fuel was sprayed behind the valves. This kept them clean by using the fuel as a solvent. Gm sells a solvent and a brush that you remove the intake manifold and spray/scrub the intake valves. Depending on how you drive this vehicle, this should last many miles. But I’ve seen this last as little as 6000 miles. This is dependent on your driving conditions. Good vid and at least you got that noise fixed.
Yeah once you start getting excessive blow-by and TPS codes and variable valve Solenoid codes the motors done bad design all around The electrical problems on these motors are too many to list
Your alternator "knock" was probably being picked up by the knock sensor, causing the ecu to adjust ignition timing. The intake gasket may or may not have been faulty also.
That flattening is called compression set, all elastomeric materials will take a set after prolonged compression an heat adds to this issue, elastomers are really highly viscous liquids, its just a matter of time before this happens
My 2002 2500hd with the 6.0 wouldn't stay running when cold once it was warm it did fine. I replaced the factory intake manifold gasket with Felpro. Been working flawlessly! My understanding is that GM factory intakes gaskets was junk and they changed the material later. They shrink when they are cold, once warm air flows the expand back to where need to be. I think i read to use flepro.
Check the valve clearances. differences in valve lash greatly affects valve overlap. If I pull a valve cover for any reason, I do that, just to look for obvious problems. Injection systems are very accurate delivering the same dose of fuel to each cylinder. It's extremely important, that the volumetric efficiency of each cylinder is exactly the same. If some cylinders are rich, and others lean, the O2 sensor will pick a "happy medium" causing a power imbalance, and, higher emission figures. you can get some clues, by pulling and reading the sparkplugs. another possible vacuum leak may be the vacuum brake booster, or, the heater vent controls. Remove those lines from the manifold, plug them, and see if the engine runs any better.
I don't understand what you mean by "never touch your factory intake manifold gaskets".
Trailblazer and Envoy intake manifold, bolts, back out overtime with hot and cold cycles. I chased a intake leak forever until I found a couple of the bolts in the back were loose.also make sure you clean the throttlebody. These trucks are very sensitive to that.
Wow! My vehicle has 446,000 miles on the odometer. Believe it or not, I bought it with only 11 miles, back in 1996. The engine sounds wonderful.
You give me hope - I'm at 292,000 miles thanks
These engines are known for pumping the cylinder head full of oil(prolly bc gm was scared of grenading engines with the new vvt/dohc setup) and those spark plug gaskets will seep oil especially on the inner spark plugs(cyl 3,4) and coils causing intermittent misfires that often go unnoticed for very long times.
I have an 06 trailblazer that im going to continue doing lots of work man, thank youuu!!!
Man, your editing quality is great Jimmy. 96 K2500
Nice truck!!
First thing I do when diagnosing an engine noise is release tension on the accessories belt and run the motor for a few seconds. If the sound goes away, it’s an accessory. Troubleshoot alternator, power steering, AC clutch and water pump as necessary.
A lot of speculation as to your issue. My recommendation would be to buy a scanner that has 'mode 6' readability. I personally use the Blue Driver. It has lead me to the source of multiple small issues (including random rough idle). Firing the parts cannon at something is great for learning. And more power to you in that. But, it can get expensive. And it doesnt jave to be. Keep on keeping on.
Thanks for being you, as always educational.
So nice of you
Mass air flow meter it is possible to clean them with electric contact cleaner spray on heated wire with it removed form car put in plastic bag so the cleaner doesn’t evaporate and give it a good spray . Then let air dry 👍
i would check air fuel pids cause if there was a vacume leak then u will see it in the fuel trims
What you say is true but that takes an experienced technician to interpret, and the right equipment. And it may cause you to suspect a vacuum leak but NOT tell you where.
There are several other ways to find vacuum leaks that require less technical knowledge and will take you to the source.
Maybe the mass air flow sensor? Similar issue on older Chevy's I have worked on in the past and it was the MAF. Going to do my valve cover gasket soon as well for the same reason of oil in some of the spark plug holes.
Did you change the throttle position sensor? Sounds like a possible TPS to me and should be a pretty quick change
I'd run a few tank fulls of fuel injection cleaner and wait for the results before doing anything else. Go heavy mixture each time.
The new gaskets and grommets look like flourosilicone (blue) vs most likely silicone. The flourosilicone is five times as expensive but has superior resistance to petroleum products and oxidation over time and should have been used by GM from the get go.
Check the tensioner pulley. They have a tendency to wobble and cause a noise at idle. Watch for wobble with a go pro.
I had the tensioner pulley go out and snapped the belt. Luckily the tow truck driver diagnosed the cause and he drove me to the autoparts store - and then he called his buddy to install it for me (cash). Wow - I got saved from being stranded on the weekend.
Do a cylinder balance test and like previously recommended, look at misfire data. If they dont prove out, you may have a dirty injector.
Recommend checking coil packs (ohm and Meg), fuel filter, check readings for MAP, MAF, and TPS, look for cracked vacuum lines. These are some items that I have chased in the past. Don't just throw parts at it, try to verify bad parts. Great work on finding the bad bearing in the alternator. I've had that one before too, lol.
THESE IN - LINE 6 ‘S ARE VERY TEMPERAMENTAL, FOR THIS REASON I ONLY USE DELCO / DELPHI REPLACEMENT PARTS , I HAVE 230 K ON AN 02 TRAILBLAZER IT STILL HAS THE ORIGINAL ENGINE , ALTERNATOR NO BEARING NOISES !!!
Suggestions. Take the coil packs back out and use some dielectric on the plug ends and clean the oil out of the plug wells.
definitely
The engine mounts can cause a vibration or also that one may feel as a loping at idle. I had to change my 2004 Envoy engine mounts and it made a big difference. The throttle body should be cleaned gently and no cleaner run down into the electronics that operate the throttle. The throttle plate is not supposed to be moved by hand either.
I've own a 2004 Trailblazer for 15 years. I bought it with 65k miles. It has 191k miles now and still has 4 stock coils. It run great and has never fail an emission test. People trip me out when they change all 6 coils when the engine start to run funny. When the coils are bad. You will know it because you will get a skip.
7:09.. For 65K, that engine is clean! I had a 2007 Mustang GT, it would stall out, glitch, and throw codes for cam position and crank position codes.. One day I went to start it and the brand new battery was completly flat. That's when I realized it was a failing alternator the whole time.
fuel system next
Thanks!
Smoke the intake and valve cover etc. This is a very good way too either find a leak or eliminate them from the diagnosis. You also could have something affecting your fuel system, you really need a scan tool to check that , and many other things. You don't have to have a cel for something to be wrong. Hope this helps.
I went all GM genuine gaskets when I did this job. Did throttle body gasket too
Have you tried a compression check?
I was an auto mechanic in the 80s for 8 years. I thought those cars were a pain to work on with all the emissions controls and the start of electronics controlling everything. Hats off to the auto mechanics today you really earn your pay, the way these cars are built today.
Had a rough idle on my 09 impala. Needed work on the tps (throttle position sensor) and I also cleaned the idle air intake and put in all new air filter. This solved the issue, but it’s also worth noting that I did put in a new injector wiring harness. This was at 235,000 and the engine previously was running on all factory parts (replaced the serpentine belt at 240k and spark plugs and plug wires a little before 235k). I reused the original intake manifold gaskets and it’s been running like a top aside from a small evap leak that’s probably a gasket that I should’ve replaced when I did the wiring harness
Replace your vvt solenoid, and ohm your coil packs. Even new delphis have been faulty. The problem should go away. I chased a missfire on my 4.2 for two years. Injectors, plugs, purge valves, regulators, fuel filters,pump, in the end it ended up being a faulty coil pack, and a bad vvt solenoid. It ran perfect after that. Had gobbs of power and gas mileage was great. Unfortunately the 4l60 left the building shortly after.
$4K for a Reman transmission - and I'm hoping the engine will last another 250,000. hahaha. I put an external OEM Magnefine inline filter on the transmission - runs way better now.
Hi Jimmy
Concerning the ruff idle, sometimes running the engine at lower rpm at idle can cause a ruff idle and intermittent shut off because the engine is not getting the right mix of air and fuel, try turning the idle up.
E.G. If idling at 500 rpm try turning it up to 600 rpm and so on.
If that doesn't work try a adjusting the air to fuel mix to see if it is that was the cause of the ruff idle, if all is controlled by a ecu then a retune may be needed of the ecu settings.
If that does not fix it then the wiring loom needs to be looked at because the ecu and the wiring loom especially the connectors to the sensors are a weak point in the electronic fuel control system.
Thanks! I’m considering all ideas. 👍
When I had similar idle issues I cleaned the throttle body and that solved it. I only had 50k miles on it but there was already carbon buildup on the throttle body.
Thanks, I did do that not too long ago. It already looked decent but made it look brand new. 🤷♂️
Check into your downstream O2 readings. Compare it to where it should be... My father in law changed the transmission out of his 06 trailblazer I6 due to a rough idle and a "slip" condition. Turns out his catalytic converter was quite plugged, but plugged enough to set a code. Weird I know but changing out the cat fixed his problem... Don't know if that helps but it's worth looking into.
I had this problem as well
I diagnosed by drilling a 1/8 inch hole before the cat and measuring the exhaust pressure using a vacuum gauge (very cheap at harbor freight)
Mine was also rattling, almost as though a chunk of material broke off...
I was throwing all kinds of codes too it was a diagnostic nightmare!
Thank you bruv. Your transparency is appreciated.
you must be from bromley
90 chevy truck butterfly in exhaust was rattling once in a while , which sensors picked up as engine knock adjusting fuel causing rough engine running, swapped about a hundred things before one thing standing on passenger side it rattled and engine acted up.
Mr parts cannon! Auto zone loves guys like you 😂😂😂😂😂😂
Did you happen to check spark plug tubes for oil? I need to do this to my 07 Trailblazer. Not looking forward to it.
The rough ideal if the battery was disconnected probably the vehicle is just having a hard time relearning its map (An engine map is essentially a table of data that is used to tell the engine what to do in certain situations.)
I used cheap Rock Auto Coils, Injectors and used alternators off Ebay to keep my 408,000 mile NY 05 Colorado on the road. I used Mobile 1 since brand new and changed oil every 6000. All the rough running I've ever experienced is due to harness corrosion especially to coils and injectors. If you don't tighten your coils enough. You will get oil in the plug holes.
That stumbling can be tough to diagnose, especially when no engine light comes on. There are a couple things you can check if you have an OBDII reader. Most obd readers give mode$06 data, which has test results for the monitored systems, there could be logged misfires on a particular cylinder. And then checking the total fuel trim (long-term fuel trim + short-term fuel trim. Or ltft stft.) Most manufacturers won't set a fuel trim fault until the total is +20% or -20%. Fuel trim is a command, i.e., sensors telling the computer add or subtract fuel. That rattle noise at the beginning of the video souded like a water pump or fan clutch failed, and I've experienced a faulty fan clutch causing idle concerns on many vehicles.
There's still things to check, all vacuum hoses and fittings, smoke test if you can, check short term fuel trims with a scan tool, it could be the isc.
Hi Jimmy, out of curiosity. Have you replaced the engine coolant temp sensor by chance? The 4.2 relies heavily on every one of its sensors to run correctly, and a flaky sensor can definitely cause it. If possible, I would do a fuel pressure test to be on the safe side. The factory rated pressure specification is 50-57 PSI, anything less is typically a fuel pump. If the fuel pump needs to be replaced, stick to BOSCH (they provide the OEM fuel pumps for the 4.2, and 5.3 Envoy/TB.) I would give the MAP sensor a good cleaning (or replace it, its a relatively cheap part). Since the 4.2 was never equipped with a PCV system, all the oil/blow-by just gets sent back through hence why the intake manifold had that gunk around the ports. The MAP sensor is located at the top of the manifold next to the throttle body.
The rough idle/stalling at a stop were usually linked to the throttle body being dirty, but since you've cleaned it you MAY need to do a relearn (if you haven't). The procedure for the 4.2 is;
Disconnect the negative cable
Leave battery disconnected for 30-40 minutes
Turn key to ON, do not start the engine or touch the gas pedal. You may/may not hear the TB actuating during this time.
After leaving the key to the ON position for 5 minutes, do not turn the key to the off position, instead start her up and let her idle for 10-15 minutes.
Drive around to get it to operating temp, and see if that makes a difference.
Otherwise, I would suggest getting a test done on the fuel injectors.
Do a compression test
Than a leak down test to see if there's any problem with the cylinders
You need a good baseline
Was there any slack in timing chain? Takes very little slack to throw sensor off
I tried moving it and it seemed tight.
Nice job Jimmy.Have you checked your fuel pressure?
One thing that comes to mind is PCV system and/or something like the oil cap gasket or dip stick tube seals.
how much fun was it to get to that last bolt by the firewall for the intake manifold. iykyk
You need to swap out the Winter air for Spring air in your tyres, mate.
Cheers from the UK!🇺🇸🇬🇧
Did you reset the pcm after taking throttle body off.? I didnt do that on mine at first and it was idling really rough until i did
It's supposed to reset automatically though - if you disconnect the battery right?
also check the MAF sensor if it has one
I was about to suggest the same thing
I had many cases where MAF/MAP gets wet from oil/moisture and it trows the drivebility of the car way off - sends wrong data to the ECU and the car starts misfiring, dying and all sort of wierd stuff
It’s new.
Is that cleanable?
I had a similar issue with my RSX (acura integra), turned out to be a vacuum leak! -they are way more sneaky than you'd think, other things i would check -upstream 02 sensor, catalyst & finally (not very likely and I have no idea how you would confirm but.. the transmission could potentially be loading the wheels more than expected in first gear?)@@1RoadGarage
edit: also, is there a chance you just aren't used to the inline? haha -you gotta remember secondary balance is not what they're about, top end power is what inlines are for!
@@1RoadGarage Yes. Very easy to do, just need to use maf cleaner and be extremely gentle with the spray. Let air dry, then reinstall.
I'm not good w/sensors but could the knock sensor be picking up the alt noise?
Ruff idle is usually a cam position sensor and or crank position sensor and your around mileage they will need changed give or take. Also when the catalytic converter starts plugging up it will cause weird ruff idle and other symptoms that are not consistent at all.
Almost wondering, IAC? If you've already replaced it, Mightn't it be bad from the factory?
So what about the third gen Sienna? How are you supposed to change the spark plugs without removing the intake manifold?
A fuel injector causes misfires too, usually gets ignored, a noid light set helps. If it is actually picking up a misfire on a particular cylinder, you can swap injectors around to duplicate a misfire on a different cylinder. Check fuel pump pressure, low fuel pressure can cause a boggy idle and a dead spot on acceleration. If there isn't a misfire being picked up, have the exhaust backpressure tested, that can cause an engine to be sluggish at low RPM
Also check for a clogged cat. I used "cataclean" recently on my 2007 hummer with 3.7. It runs better and better fuel economy. I also used it on my 04 6.0 powerstroke and fuel millage is better. Clogged cats can cause rough idle.
I agree with the last guy. Check your fuel delivery system! You could have a failing pressure regulator or a damaged fuel pump!
You need a good scanner to check your computer for error codes. After what you have done to that car i would be checking the fuel pressure. How long is it since you changed the fuel filter?
Do you recomend Amazon for the new parts?
Did all this on my '04 Envoy about 4 years ago at 260K miles, plus changing the fuel injectors. She's got 296K on her now. I notice you didn't show getting to that rear-most intake bolt. What a PITA. By the way, I thought mine was idling rough...change your motor mounts. Not that hard. Makes a world of difference.
Bro. Not to be negative. But 65k on the third alternator and having issues with the engine, Maybe the problem is the oem parts. Was a good video. Get a computer so u can check different perimeters like ur fuel trims and o2 sensors, that kinda diag information is critical when dealing with rough running engines
Do you need to do a throttle body relearn since you had it off that should take care of the issue
I thought the computer would figure that out since I had the battery disconnected for days.. I’ll look into it thanks!
Jimmy could it your throttle body sensor that’s causing the ruff Idle .
On the alternator. Pull off that back plastic piece if it's easy to take off. You should be able to see that back bearing cover. Make sure the cover is there. It's often a piece of sheet metal pressed into place. Sometimes they forget and that'll cause dirt to be sucked into the bearing. Then it'll go bad and make noise. I always check.
Sounds like Idle air solenoid, usually just cleaning them works, but cheap to replace. Also check the temp sensor reading with scan tool (sensor in intake)
Does this car have a gas tank vapor absorber? I had a similar story, I used smoke to find leaks, they were there, but they only affected the corrections that I looked through the ELM scanner. The main reason turned out to be a stuck adsorber valve, which did not close by about 5-10%. And also, everything is fine, but the idle is not smooth. Replacing the valve solved the issue.
Haha, your thumbnail caught my attention, I have the 2.9 version of the Vortec inline with the same manifold and everything really, I actually have a rough idle on my truck, it's kinda on and off but not nuts, maybe I'll take a look at these gaskets now, could be the culprit, cheers!
Some of these have a metal intake alternative. My Buick has a later style metal alternative I’ll be switching to when I go to do my lower intake gaskets next weekend. Got the adapter plate, & changing the lower intake elbow orings or just new elbows cuz it already has the metal ones.
Try some fuel cleaner next on it, & see if that helps.
Fuel injectors clean and how old is the fuel filter? I'd double check for vacuum leaks. I used to just get a water bottle and put a small hole on the top and squirted over the engine. Definitely do the basics first like these. When I an auto tech, a lot of idle issues were due to maintenance like injector cleaning.
I would suggest maybe changing the engine and transmission mounts. It's possible that the rubber in one of them is ripped and causing a slight shudder.
I had the alternator for my 97 Olds 88 go out with bad bearings. It was an upgraded Mechman alternator and the bearing towards the rear totally blew apart and was wobbling around. Thankfully I could limp home and had power if I let the engine idle but as soon as I gave it gas it would moan really bad and drop the voltage.
Is your fuel filter located inside the tank with fuel pump or is it outside the tank, my Pontiac torrent has that idling problem too and my fuel filter is inside the tank
Best tool for finding that tick is a mechanics stethoscope. Best tool for finding a leak is a can of carb cleaner. Just spray around any potential vac leak and listen for stalling.
While we are throwing parts at it, replace the knock sensor and crank position sensor. Both located next to each other on the driver's side engine block down low. Access from driver/front wheel well (Envoy on jack stand) and underneath. I had to replace the CPS on my 8.1L Burb because it was stalling out intermittently while I was driving. Age could be getting to motor and tranny mounts, as well. Also, a long extension from a part to the ear is good for finding sounds, just be real careful on a running engine not to get into the fan or belts.
Gunk on throttle body plate. Give it a good cleaning and see if it changes things. My 5.3L 2013 Avalanche's throttle plate was pretty caked. A toothbrush with some intake cleaner smoothed things out quite a bit. Still not perfect but does WAY less throttle wobbling.
I was getting 14.3 mpg for 7 years. I replaced the map sensor and my mpg has gone up to 15.3 mpg.
Does it have fuel filter that is not in the tank? If so I would change the fuel filter. What brand of spark plugs are in it? I would put the exact plug in that it left the factory with. Should tell you in the owners manual. So it was doing this with the old coils and you replaced the old coils with new coils and it still does it? Do you get a random cylinder mis fire code or are you getting a specific cyclinder misfire code? What is the live stream data saying?
love the content. keep up the great work
you get signs what is the problem. noise from alternator refer that camshaft not balance, it's mean that becasue camshaft spins not in center then alternator will have damage to alternator bearing.-------------------------------------------------------------------------------------------------- conclusion : 1) one or more of engine cylinder or valve had leak, you can easy check that with ODB (check negative pressue on idle), because of that the camshaft will not be balance and you will get also oil leak. ----------------------------------- i think it not worth to fix.