Chevy MYSTERY Misfire - Part1 ('98 K2500 Labor Day Special)
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- เผยแพร่เมื่อ 6 ต.ค. 2024
- Just another Chevy truck, just another misfire...right? Not so fast!
There is more lurking under the hood on this 1998 Chevy K1500 than just a bad spark plug....
Took a while to nail this one!
Repairs coming up in Part 2 :)
Enjoy, and Happy Labor Day!
Ivan
The reason it smoothed out under load is because a vacuum leak doesn't have as much of an effect then because you're adding fuel to compensate for unmetered air coming in through the intake leak. Then the air fuel ratio more closely matches what it should be. Great video I'm glad to see technicians doing a proper diagnosis instead of throwing parts at it.
Most of the vacuum is made at idle, not at higher RPMs. The MAF was also reading way off at idle, 9.6g/s should be closer to 6.8g/s, so that left valve cover vent tube into the intake before the throttle body was clearly distorting it at well. The MAF is before the vacuum tub.
Vacuum drops to near 0 at WOT doesn't it? That's what "vacuum reserves" are for(as I understand it)
That is not completely accurate. Manifold pressure increases to near atmospheric pressure as you open the throttle blade. The pressure differential between atmosphere and the intake manifold is less thus air does not travel through
the leak point under load.
Lol Ivan, sounds all to common problem!! Had that exact same issue with my suburban! I bought mahle intake gaskets instead of felpro as they're more solid built. I had pcv issues with high idle. I indeed replaced the pcv with oem. Did not fix it, found out that i was getting to much vacuum in the crankcase, the gaskets were bad, as the water jackets clogging up. Did full flush, fresh gaskets really cleaned the surfaces, never had a problem since. 260,000 and still going! They're really well built, solid motor if well taken care of.
Interesting failure mode! Normally they just leak coolant everywhere...
Lol! Yeah very weird 😅
Hi Wes Great to see you here, how long you've been watchin russian repair videos?
Yep these are notorious for sending coolant into the engine. I’ve heard a lot of 5.0 and 5.7 vortecs knocking from the coolant oil sludge taking the bearings out.
@@mjmcomputers
That's called a lack of maintenance. In other words, neglect. Not a vehicle fault.
@@wildman1137 bad design on the original intake gaskets on these. They normally fail at under 100k.
That's a a good diagnostic boy ,,, truck is probably older than he is,, we had a lot of trouble with those intake gaskets leaking on those engines normally coolant haven't seen one with vacuum that's a good catch,, great job
A little schematic diagram showing PCV valve, idle air valve etc would help in understanding the issue. Thanks as always
Very cool diagnostics ! Old Chey's never die, they just get a bit of Russian help on occasion ! Listen closely to the audio in this video. Shhhh, listen,... You can hear Bob Seger singing......
Great find!
The customer reported no AC. That's one thing they know that isn't working because they're *HOT!*
I have a feeling that the clutch gap is getting too wide and the clutch isn't closing all of the time. Saw this on my '03 Forester.
Try removing a shim on the clutch to close the gap. The other solution would be to replace the clutch or compressor.
Cant remove a shim no shims on these you just get the GM compressor hub/ clutch tool and push the clutch fitment a little tighter. These compressors are not good. Alot of case leaks. Now all the replacements are china. Every one. even GM. They have some nasty looking compressor on it and a high side cap that looks busted off in the valve
@@GhettoWagon thanks for the information!
As soon as I saw the high idle and zero IAC it was a vacuum leak. Good to see you didn't go down the low compression rabbit hole. Easy to overthink things sometimes, but back to the basics and it's just a vacuum leak. Hopefully just the gasket like you said and not some cracked intake runner that never happens...... But would make for a good video!
As soon as you said misfire with no code and high idle code I just shook my head and reached behind the seat of my 95 burban and grabbed the intake gasket set. Its a common issue that many people don't really realize. It usually doesn't manifest with many symptoms on these except a slightly high idle witch most don't really notice a shake at low rpm but when u hammer it everything is perfect and you can see the misfire disappear. It can be frustrating especially if everything is checked out ok and you find a worn out pcv valve or bad vacuum lines and assume that you nailed it. If this engine doesn't use the plastic and rubber o ring style intake gaskets (idr witch year they started using that style but 98 is close to the change) as much as some will reeee about it best long-term solution that I've had great longevity from is to coat both sides of the entire gasket surface with rtv and flush out the dexcool and put green back in it. I do the rtv on the gaskets cause the dexcool causes pitting and I have found that using rtv just around the coolant ports does prevent coolant leaks but it causes the gaskets to blow easier and cause more vacuum leaks. I currently have 3 years and most of 100k miles on the last set I installed. Generally speaking on most any SBC 5 years seems to be the time frame that the intake gaskets seem to start leaking coolant or vacuum or both. The gaskets get hard and brittle and then if you get nice and warm while working it hard by towing heavy wagons or anything like that. Doesn't take much to get a leak at that point. We have had the 88-98 chevy trucks as our farm trucks for 20+ years and it is almost clock work to have to do the intake gaskets on them at 3-5 years always ends up being july-early September during the dog days and ironically right during the heavy hay and haylage season so hauling wagons and getting them nice and warm under heavy load and as soon as I get a break in the fall I swap a new set in before the winter weather sets in.
Sounds like you have a lot of experience with these trucks Clayton! Which brand of gasket do you prefer?
@@PineHollowAutoDiagnostics felpro. They tend to be what is most commonly stocked. I don't really see much difference between the different brands. Only so much that can be different and if your gonna apply rtv I've honestly cut a cereal box and made a set of gaskets a few times in a pinch on on the side of the road after blowing the coolant port and leaking fast. If you've done it a few times can be changed out in about an hour (atleast I could prior to having 3 discs removed from my lower back now its closer to 2 hours).
@@claytoncoolidge992 I believe Felpro and Victor are the best choice. they both tend to exceed GM in upgrades and quality most.
@@claytoncoolidge992I was a gm dealer tech for years and I agree. Doesn't matter much which gasket is used if you use rtv to compensate for the pitting. Being in the aftermarket world now for over a decade I find rtv to be the savior on many issues. Early 2000s Toyota's with common timing chain tensioner leaks at right rear of engine bay is a great example. This leaks oil all over power steering pump which commonly gets misdiagnosed as the issue. It's an o ring that fails on tensioner...and even if you replace the tensioner assembly (comes with new o ring) or just the o ring... This will always fail again within 500 to 10 thousand km in my experience. Adding rtv to the o ring has eliminated all comebacks. I like to follow service manual as much as I can until i get tired of comebacks lol. There is one manufacturer out there that I won't mention that if it has a transmission oil pan leak..i get rid of gasket and don't order another...just clean surfaces well and use red Rtv... hasn't let me down since. I've seen the thin cardboard trick with rtv before when I lived in Asia for a while. Works good. Even saw leaking I ejector o rings on heavy equipment fixed with thread ripped off the operators shirt... 😎
@@jeffreywilsonrubikscubeonb2428 lol ikr I'm pretty sure I know exactly the trans pans you are referring to 😁 i totally agree though if I can do a job once for someone and not have to worry about a come back simply because I can supplement the oem and improve upon the improved redesign then im all for it. Been many times that a couple of extra seconds to toss a little rtv on a gasket made all the difference. The best one I've ever pulled off was on a 1953 john deere 60 head gasket I was 16 or 17 so I can't claim that it was skill or knowledge but it was pure genius. Head was perfect except for a very very small chip that was too deep to machine out and the tractor not only had sentimental value to the customer but it was also all completely numbers matching original tractor. After several failures with multiple shops including the dealer I offered to look at it and see if I could find a way to get it to work and seal and stay sealed. I replaced all the head studs and then used one used gasket and one new one and put red rtv in between the 2 gaskets and on both sides of the outer faces and put it together completely disregarded the torque specs and put a 3/4 drive breaker bar with a 5 foot cheater pipe on the end of it and slowly working in the proper pattern but making sure that I started and ended each pass on the stud closest to the bad spot on the head cranked them as tight as I could possibly get them. And then let it set empty for several days. I never filled the coolant till I got the tractor running and warmed up a couple of times dry. When I filled the coolant up there wasn't any sign of leaking till it built up to full pressure in the system and was very very small. So pulled the valve cover and had the customer help me to tighten the bolts while engine was hot and we cranked another half to 3/4 turn out of them. 21 years and its never blown again it will leak a tiny bit if you are working it too hard at full throttle on a hot day but once u see it leaking as long as u back off the throttle a bit it stops leaking and is all fine. Its never leaked coolant into the cylinder since I did them witch was the major problem.. a small occasional external leak is not a problem considering
Sweet Diag. Ivan. Love when you do are great country holiday specials. Hope you and your family have a wonderful labor day. Say hello to your brother in my home state in Indiana for me. My friend and I just got the 1986 kawasaki 900 Eliminator running. Had a coolant leak. All is well now. 👍👍
Happy Labor Day to you too, Richard!
The Intake gaskets are notorious for going bad on those. There are premium updated gaskets that hold up better. Make sure the manifold isn’t warped as well.
I never had an issue with intake gaskets. I think the problem arises when the mechanic isn't careful enough setting the intake and displaces a gasket. I used shellac to hold them in place and put a dab of sealant on the joints and very carefully set the intake down.
I’ve had five of these trucks and every one of them had to have the intake gaskets replaced between 100-120k miles. Piss poor gaskets. The new upgraded gaskets was the fix.
I think the intake manifold gasket makes sense cause cyl 7 was misfiring a bit as well as 5 and they are neighbouring cylinders. I am surprised you never mentioned cyl 7 misfiring. I am excited for part 2 cause I am wondering if the intake gasket is literally just another red herring lol, but the crankcase was under abnormally high vacuum for sure.
Ahhh, you heard me screaming at my phone. Intake gaskets!! Misfire worst at idle (high vacuum - throttle plate closed) the excess air creates an extremely lean condition in cylinder #5 with little to no contribution. However with a MAF vehicle, I would expect lean codes on both banks. But considering the age of this thing it doesn’t surprise me, doesn’t even set misfire codes! Also good find with the PCV valve. Can’t wait to see the Russian repair in part 2…
Haha! Me to! We must have been making a hell of a racket.
MAF was reading 9.6 to 10.1 at idle, way too high. If the computer was following it, to maintain stoichiometric, it would be adding fuel. It should be 6.3 to 6.8g/s on that rig. Remember, it's got the old skool O2 sensors... That valve cover tube goes into the intake between the MAF and the throttle body likely tricking it by pulling more air into the crankcase at idle than would normally get by the idle circuit, causing the higher reading in MAF.
Faulty fuel pressure regulator will bleed into cylinder 5 on these spider injection sbc engines and cause this #5 misfire. By the look of that plug.. I'd say it's possible
@@RG-cd3uf or cause an intake backfire and blowout the upper intake seal or crack the upper intake manifold.
Thought for sure you nailed it with the injector test, my immediate thought was head gasket slight coolent intrusion into 5
Can you bend a rod starting the engine after injecting fuel into the cylinders with the engine off??
@@Garth2011 If you dump enough fuel in, yes.
Great video. I've owned a 98 K1500 with this engine since new and I'm on my third intake manifold gasket with the last one being replaced at around 75-80,000 miles. There have been three revisions of the intake gasket over the years and my truck has version two. I'm at around 142,000 miles now and so far the intake gasket is still good.
Years ago I had a high idle situation with this truck and it ended up being the thermostat was stuck open so the truck never warmed up to the correct operating temp and had the idle at high all of the time. New thermostat and idle returned to normal.
The AC compressors on these trucks are a know issue for leaking and that one is definitely leaking so the owner will be looking at a compressor replacement in the near future. There are one piece case clones out there that are way better than the HT6 that these trucks use. I've been using a Seltec-Valeo compressor on my truck for years and it's still leak free. I also own a 98 K3500 with the 7.4L big block and have replaced it's compressor with a clone as well with no leaking problems.
I like to use the felpro rubber backed steel intake gaskets on those way better than the flimsy plastic original type.
Don't ever run the spark plug outside the cylinder like that unless you want to start an engine bay fire!
I've been fighting an issue in my '98 Yykon (5.7 vortec) for a couole months. When I bought it, I performed a full tuneup [iridium Spark plugs, wires, cap and rotor- all acdelco, air filter, oil change using Mobil1 high mileage full synthetic, K&N Gold high-flow oil filter]. Started out as hesitation at low idle, then progressed to hesitating and nearly dying unless the engine was cold, then progressed to the same but would even out if the RPM was above 2,000.
I replaced bank 1 and 2 o2 sensors, no luck. Less than 3k miles after oil change, it was black and smelled of gas. I got to the point of thinking a valve was getting stuck, so I used Lucas full synthetic high mileage oil treatment, ran the engine above 2,000 RPM for several minutes, then noticed the problem was 90% solved- it runs much better, but not entirely perfect. So I presume my diagnosis is correct, and now I gotta dive in to the valve cover and inspect rocker arms and valves. Wish me luck.
Excellent! looking forward to pt 2. I caught the vac leak early on only because I watch all yours and fifteen or twenty others others every week for the last five or ten years. But I have little practical exp. Love this stuff but I'm glad I don't have to be doing it. Not a lot of stuff in the bay in the way...Should be interesting. With all the leaking the A/F ratio didn't change that much I guess it could compensate. See what you find.
As soon as I found that much vacuum out would come the Avoca Smoka! LOL
Looking for part 2 to come!! Great diag Ivan!
Ivan, the HR6 compressor on this engine is notorious for leaking freon. And from the looks of this one it is too. Someone may have recently recharged it.
This engine is known for intake manifold gaskets going bad at 100,000 miles. This is a strong possibility . I have 3000.00 miles on mine and have had to replace this gasket twice
Good video....he walks you through his diagnosis and at the same time
I would add onto the parts list, 8 plugs, a set of ignition wires and a PCV valve for good measure as they are all very old looking and the labor cost would mostly be included with the intake manifold gaskets or be greatly reduced. Spark plugs are cheap enough I wouldn't try to clean them and unless those ignition wires were replaced within 5 years or so, I'd replace them too. I believe the only internal concerns on those 5.7L are the exhaust valve stem seals tend to wear out by 76,000 to 100,000 miles.
You're 100% correct. Nice diagnosis. He will get better mileage and more power after you fix that.
Would Eric have sprayed brake clean in the general area of the suspected leak to see if the idle would change?
he would probably pull out the Avoca Smoka
It's leaking underneath the inake manifold. A smoker wouldn't tell you anything. Well, maybe when it came out the PCV valve cover hole.
Where would you spray the brake clean? No external vacuum leaks...
@@PineHollowAutoDiagnostics ahhh. Did t know that!
I always, ALWAYS check for intake problems on these engines. Vacuum in the crankcase is a dead giveaway.
A gross leak indeed. Thanks Ivan!
Magical truck runs on no fuel, I want one.
Thanks for a solid diag video. Im no expert but I feel like Im on track now to find the right solution to my issue! Thanks!
Enjoy your labor day weekend. Can't wait for part 2
Great video. Had the same issue years ago on my 99 Tahoe. Please install the Vortec marine version intake gasket, made of Stainless steel and rubber seals.
That's a great idea!
@@PineHollowAutoDiagnostics For the 1996 and later 5.7 Vortec/Mercruiser (all the same). Should be Felpro FEL-PRO MS 98000 intake set. Also, a must replace, Fel-Pro ES72224 Intake Manifold Bolt Set, they will be corroded to death. Another fail on rare occasions is the upper plenum, clean and look for cracks. If the vacuum leak issue is not fixed soon, the engine will become an internal water pump and suck all coolant into the block/pan areas. The engine will quickly overheat and crack the heads. I know this well, it happened to me.
Take care
John A 60107
You had me worried when I seen you giving up on the diag with the compression theory. I actually came across this before so I was thinking intake the whole time. Nice job.
Man Thanks for making this video you gave me a lot of pointers I been trying to find out why my 97 chevy had a misfire still at cylinder 8, I already replaced injectors and spark plugs this video really helped
I just fixed an Expedition with very low idle. So low it was dying. Only codes are P0420, P0430 and P0705. Ended up being just a dirty throttle body.
NO PARTS REQUIRED :))
@@PineHollowAutoDiagnostics Heck yeah! And thanks to you I'm interested in actually diagnosing. Instead of guessing and fire the parts cannon.
Yup, intake leaking under manifold, fixed a few myself. Same symptoms,took a few to figure out😁
3) Vacuum leak? That's why it smooths under load. 12 minutes in, let's see 😁
At 18 minutes, vacuum is still there with PCV blocked off due to a leaky valve cover gasket maybe? Bank with affected cylinder (as there were also a few misses on number 7).
EDIT: Aah crap, the intake manifold gasket :) Didn't think about the most obvious thing, lol.
No lean code ? What were the fuel trim numbers?
@@joebriano6090 It didn't set a misfire code either, who knows what kind of strategy the ecu has.
nice job. . . . . . . . .I am about to venture through some similar issues, I thank you for sharing bro!!!
Part two I am in !
There's your problem , lady!! Hmmmm, where have i heard that before??? Lol
good job Ivan, even though parts will be required, your going to have to bite the bullitt and put them in
Saw the RPM too high code and instantly thought of a vacuum leak in my mind haha
What I need is a video on an OBD 1 88-95 GMC truck. Been trying to solve the mystery of a dead miss in open loop, that disappears as soon as the coolant temp reaches 40* C. Parts cannon has been fired, reloaded & fired again ! Lol Everything but the charcoal canister has been replaced and I do mean everything. I have no scanners or the knowledge to use them. Could be any thing from the wrong IAC counts to a sticking push rod. Been at this for 2 yrs now, sure wish I had you around for a day I'm sure you'd make short work of it. Love yer video's, love learning from you Bro, keep fighting the good fight my friend ! PS. I smoke tested it. If it is a vacuum leak its not the intake. 94 Yukon by the way
Common problem on these older GM engines. Make sure to use GM gaskets. If I remember right, GM updated that gasket.
Nice work! Love watching your videos. Keep it up!
I recently had an intermittent misfire at idle #6...was worst no load @1400 rpm, fine under load. Opened hood while running & #6 spark plug was shaking (it was loose). Tightened plug and now it's ok. Hard to believe that small of a vacuum leak caused a misfire, but it was close to the spark.
I would bet that that A/C does need a charge because that compressor is pretty dang oily.
"Mystery misfire"
ETCG: I'll just flush the engine with this caustic chemical.
Also ETCG: The Odyssey engine blew up! I have the worst luck. 😂
He blew up the engine?? Did he diagnose the misfire? 🤔
@@PineHollowAutoDiagnostics I watched that video. When he pulled the valve cover. He saw the engine was full of sludge. So he decided to do the engine flush. It was an Odyssey with the VCM system. When it shut down some cylinders. Those cylinders filled with oil and kaboom!
@@billziegmond4943 Flushing engines was something us oldies use to do. Modern engines with modern oil not worth the risk as Eric found out.
You guys didn't even watch all the videos, in the tear-down he discovered that the engine being locking up was caused by lack of oil. The oil pickup was clogged with sludge that he suspected was knocked loose by the oil flush additive. He then went on to say he does not recommend using oil flush additives. I think he even mentioned he does not like the stuff in the video of him using it but he said he would try it.
@@lrdisco2005 Yep! 😂
I had a Silverado once that had fuel, spark, good compression but constant misfire on #2... had the converters checked...one of them on that bank was restricted
JUST went through this, 97 sierra 5.7. #5 misfire... (misfire constant, brought in from another shop, after they replaced all tune up parts.) # 5 spark plug bone dry, no fuel smell. Compression 165 psi. ALL injectors dropped 13 lbs during the drop test. Verify 3/4" air gap spark test. Run engine, fuel trim high bank 1 at idle. (Plus 20%) Fuel pressure stays around 54 psi, no drop after shut down. Owner replaced injector assy 2 years ago from Amazon. Noticed coolant reservoir low, topped off, pressurized, held stable for 1 hour. No signs of fuel in the plenum
Remove intake, #5 & #7 injectors reversed! Owner said it ran good for awhile after replacement, wtf? Verify spray when activated, re installed proper. Run engine, still misfired UNTILL eng warm. Signs of coolant leakage rear of b/1 head. Replaced intake manifold gasket, NO misfiring, fuel trim under 10. I wasted a lotta time on this diag. Gotta think!
Wonder if a smoke test would pinpoint the issue better ?? or the scanner danner method of water bottle with a tiny hole and spray around the area and listen for leak ? Great show
96-99 notorious for defective intake gaskets,you will find the hard plastic broken around the silicone. They love leaking coolant into engine there too and wreck rod bearrings on #2
That's the same thing my 95 gmc sierra 2500 5.7 did. Every 2 months I had to clean number 1 cylinder plug. It would completely fill the gap and the area around the electrode. I'd keep a new plug in glove box. Strangest thing was #1 would get fouled like that and #5 was white at tip. I don't care those gm 350s are monster tanks. Just got another one last month. Has a slight miss but that truck hauls weight and don't complain. The first 1 I bought I could pull 3 zero turns around up hills and all.
Saw the thumbnail and instantly thought "vortec injector failure"!
all classic signs of intake vacuum leak on those engines :)
on the older TBI engines, the base to manifold gasket always went bad.
Once I saw those crusty deposits on the spark plug, I figured the engine was burning oil. At first, I thought the valve stem seals were bad, as they harden and leak after prolonged service. However, given all the evidence, it's clear the intake manifold gasket is the main issue. If memory serves correct, there's a special torque sequence for the intake manifold on engines with Vortec heads. The center bolts must be torqued first, then the outer bolts. If it isn't done that way, the gasket will leak because the bolt angles are different.
Notice that the gas gauge is sitting on negative empty. Two times in my life I have run a car out of gas only to have the engine get fouled when I put in more gas. Never let a car get that empty. Assume the gas tank is contaminated with gas loving spiders.
Not good for electric tank pumps, they overheat without fuel covering them
Just an intermittent sending unit lol...it's a GM thing!
It would be good to test the egr v. before taking off the intake but its prob. fine its not running that bad
Stuck EGR should not cause crankcase vacuum surely? Just terrible performance.
@@ludvigericson6930 Right thats why you test it while your there. buying intake gaskets.
Those engines... I've suffered thru a few misfire diags on those. At least it's OBD2.
Good job iac was compensating for vacuum leak
My initial thought was vacuum leak. I've had similar experience on a 4.3 Vortec.
Hey man, I was prompted to check this video out. You're pretty decent guy. You also know how to diagnose. Good video!
Welcome to the channel man!
The first thing that came to mind were those plastic intake manifold gaskets. They will also tend to cause coolant loss and a rise in oil level.
Harbor Freight has a plug cleaner that works better than any scrapping. All the V8 GM had a oil fouling of the rear plugs due to oil /sludge in rear return holes.
Proper diag i thought you were going to leave it that, great job.What about ac concern? That compressor sure had alot of dye on it looks like it has leaking seals common on those.
I got a 97, just thought i'd check it out for future ref. All's ok now.
Hey Ivan, definitely a manifold gasket leaking internally, SD has a good case study on it. I'm guessing the pcv port in the D.side valve cover must also be quite blocked, otherwise I'd expect it would equalise the crankcase vacuum through the pcv port when the pcv valve was removed?🤔
If you had put a pressure transducer in there, you would have caught the issue fast (or at least known it wasn’t fuel related). You would have seen abnormally HIGH running compression in that cylinder at idle along with low vacuum on the intake stroke (in the cylinder). You would have also seen it in the fuel trims, which I’m surprised you didn’t seem to look at given you thought it was a bad injector. As others have said, this is a common failure, especially if the gaskets were replaced with cheap ones at some point or if the manifold bolts weren’t torqued properly. Since there are so few bolts holding the manifold to the head on the vortec engines, they tend to suck the gaskets in like that if the gaskets don’t have enough support built into them. It’s not strictly a GM issue either. Toyota had a huge issue with this on the 1ZZ engines and I’ve seen it on Kias, Nissans and Fords as well. Glad you continued to look at it further and found the real problem rather than just sticking with your assumption that it was a compression issue.
If I were doing an intake gasket, I'd also upgrade the spider injection to the improved one with real injectors. GM makes an upgrade kit that bolts right in. Better mileage and a bit more power. Not expensive compared to having to go in later and fix a popped off or cracked plastic injector tube.
"If it ain't broke don't touch it " is my philosophy 😉
@@PineHollowAutoDiagnostics If it ain't broke, keep fixing it til it is!
Also makes engine less finicky about fuel pressure.
I would have sprayed engine start around number 5 inlet manifold to check for a vacuum leak, quickest way!
Except the leak is on the bottom side to the crankcase so spraying from the outside would be a fruitless endeavor :)
@@PineHollowAutoDiagnostics Good to know. Love your vidios!
I had 3 GM Goodwrench 350 V8s installed in my 86SS Monte Carlo. They would burn oil after a few thousand miles, all 3 of them. Two were replaced under warranty. Now that I have had a few years to think about it, I'm sure using RTV for an intake gasket was the problem and it was sucking oil from the lifter valley into the cylinders. I removed/replaced chevy V8 intake manifolds many times using gaskets and I never had an issue using gaskets. Ford uses it on the diff covers. I used it once and it leaked. I hate RTV when used as a gasket.
this video is ridiculously good looking
Ivan, when you had the #5 spark plug out, how much more difficult would it have been to run a quick compression test on that cylinder?
With a vacuum leak, shouldn't the fuel trims be out of whack?
Great question! Can you explain why they were NOT out of whack in this particular case?
@@PineHollowAutoDiagnostics I have been thinking about that .... fuel trims get out of whack when unmetered air gets into the system somehow. In this case, it seems the intake manifold gasket has a leak into the crankcase creating abnormally high vacuum at idle. The MAP sensor monitors what is going on in the manifold... possibly it is compensating for the leak?
@@randymarion2466 You're on the right track with the "unmetered air" theory. In this case is the extra air being sucked through the crankcase vent hose metered by the MAF?
Ivan Maybe its has a diaphragm on the engine breather system. It could be split.
I believe my 99 Tahoe has the exact same issue and my mechanic just replaced the intake manifold gasket. Wonder if the gasket isn't seated properly. There goes more money (and labor)....
Well, i'm not tone deaf in 1 khz door chime frequency. This video saved me a trip to the audiologist... LOL
It was driving me crazy too 😂
sounds like a leaking intake gasket, the reason they don't set a code is they usually seal up after driving a short while and the miss goes away. My 5.3 has a slightly bad gasket and if I let it idle for.a while in the winter It will start detecting a miss, goes away when you drive it.
My 5.7 k1500 has had a misfire for several months..after replacing every single sensor including the ignition coil with the control module, and new distributor new plugs and wires and still misfire for several months, it turns out its the pick up coils in the new distributor. Go figure. I also replaced the spider fuel injectors with GM original injectors. Lesson learned
Ivan interesting video. Hope you and your wife have a safe and enjoyable Labor Day weekend. You mentioned the SUR R fuel connection kit. Do you have a part number? Try to adapt a fuel gauge to my 3.5 J series engine. I have the Honda fuel pressure gauge but need fittings to hook it up. Can you recommend a kit? Thanks buddy 😊👍 Artie
Check out the Amazon store!
Wouldn't the long term fuel trims also be way positive? I had a massive leak around the intake snorkel thing and my fuel trims went down 25% when I sealed it up with RTV.
on intermittant ac usually hi pressure switch on those. They drop out causing ac to shut off
Check them sticking valves. Seafoam will fix it. Or distributor cap is arcing through another cylinder
Nice shout out to Eric O.!👍
the misfire counters are there but relaxed on thes hd trucks over 8500 gvwr. If engine is sound almost always the spider even if they flow good
Ya don't know 'til ya know... Moral of the Story: Test... Don't Guess. Call Scotty and ask him to bring a box of cigars for a collaborative smoke test to demonstrate his technique.
I hated those junky spider fuel injector systems.
Why would an intake manifold gasket cause this? Is the mounting surface on the head open to the crankcase? If so, why?
Part 2 will explain that :)
I had a random misfire code -- I replaced the old loose, leaking GROMMET for PCV for a tight seal...now my '97 Silverado
runs like new.
Nice 👍
If that leak is unmetered air , wouldn't the fuel trim numbers be rich because the lean condition would call for more fuel to be added ?
Should smoke test the engine to determine where the vacuum leak is.
If the vacuum leak is internal, where are you expecting to see smoke?
Nice diag! Spray the intake with carb cleaner or brake clean to confirm the intake leak?
Was waiting for new video🤙nice job
Very interesting video. I've got a 1999 GMC K1500 Suburban with the 5.7L engine. I'm getting misfires while at stop light and idle is at 600. Also motor shakes sometimes between 1000-1900 RPM. Usually while in overdrive. Recently tried changing the spider injectors with ones made in china, but they here bad and got my money back. I've changed just about every sensor on this Suburban with no luck. Think I'll take the intake manafold off and see if gasket is in place properly.
Does your check engine light come on with this misfire?
@@jonschwartz9669 No check engine light. I have a code reader and there are no codes stored. When I come to a stop it takes about 5 seconds before symtom shows up. Suspecting a bad fuel injector.
@@rogermerritt6470 Try a bottle of recline fuel treatment it has the highest concentration of PEA this is the best carbon cleaning product on the market also a manifold gasket that leaks can cause misfire a weak fuel pump a dirty fuel filter a weak fuel pressure regulator under upper manifold plenum its either fire or fuel
@@jonschwartz9669 I have replace the fuel pump, but not the fuel filter. The lines are just so rusty in that area. The engine runs just fine when it's cold. Computer module was swapped out with no change. Very strange problem.
Hmm .. idle system .. intake leak (use unlit propane torch, point it at suspected leak spots .. RPM will change if propane gets in the intake), compression check .. head gasket checks …😮
remember the k.i.s.s. principle keep it simple, add what you want or feel like.
I think there was not enough fuel in the tank for the misfire monitor to run. unless the guage did not work it was reading in the red 🤔
Use some of the liquid sealent and make a new gasket with some goup :)
thing is 1 spec of carbon on the tip of a injector can cause flow cone to be wrong and misfire even if it flows
Great video