Your ability to break down complex concepts into understandable (and often hilarious) terms never ceases to amaze me. I've learned so much from these videos - not just about automotive issues but about the troubleshooting process in general. Thanks for the time you put into these!
In a Buick I worked on 40 years ago I had a similar situation. The car ran fine at idle... but as the load and speed went up the engine bogged badly. The problem was a collapsed exhaust pipe. Not that you could see any deformation the outside .. but the pipe delaminated and one layer collapsed and choked off the inside. I couldn't believe it until I sawed it open. Replaced the pipe and all was well. Kept that pipe on the wall for years. Phil
GM used a double wall exhaust pipe on many vehicles from 1969 to 1973. If you were driving with a hot exhaust pipe [ high speed cruising for example ] and went thru a large puddle of water, the cold water would hit the exhaust pipe, then the inner pipe layer would collapse and block the exhaust flow. You had to cut the pipe open to see it most of the time as it would do this near the middle of the length of the exhaust pipe. I saw this on a Bonneville and an El Camino..
Sounds like a problem you’d see in a cast iron plumbing pipe which will “delaminate” over time. Went to put a pipe plug in once and couldn’t get any to fit. Even chipping some away
I'm waiting for you to get ahold of an old 70's, 80's model without all the high tech computers involved. All your "gadgets" are over my head. Love It.
The 3800, best V6 ever created. I miss mine already. Small, light powerful and can be swapped out in four hours. A thing of beauty is a joy forever. With the supercharger this thing was fast as well.
23:44 I need to see this video it really helped me with my problems with my 2002 Chevy Silverado I could not figure out what was going on with my truck until I saw this video. I had the same problem with my exhaust stopped up
Another great video. So glad you decided to make it once you saw the issue and its magnitude. I'd love to see a follow up that shows where the blockage was and the "after" readings.
IMHO you are too quick to beat yourself up. It was a good hypothesis, and you went through the steps to prove it. The easy stuff is easy, and if you have to get dragged through the mud a little bit to satisfy yourself on the hard ones, that's okay. Every decision you (or anybody) make is done with consideration of the cost associated, based on previous experience. This didn't strike me as too high of a cost to really get a solid diagnosis. Sure it's a bit of time spent, but that time spent will yield positive results for you (and now me) in the future, so it was time spent but not time wasted. Once again, thank you.
You the man Eric nothing like watching a real pro do his job. Not many mechanics like you anymore really wish you worked in Maine you would have a new customer. Keep up the great work! Really enjoy your videos watch them daily!
I watched a couple of guys do these bad cat bad flow video's on different cars... the performance varies a lot... i am 99 % sure i have this issue and possibly i installed my distributor in a tooth off because it used to be drivable and idle like a kitten...but when i drove it ..it lacked half its horse power bucked and hesitated intermittently... thax for all your great repair video's...
hey Erick.I have been watching your videos and noticed that in every other video you have different scan tools. and was wondering if you could make a video comparing the different scan tools. thanks for sharing your knowledge.
You guys want a good laugh turn on the self generated captions on this and watch it again. Love the videos keep up the good work, (not on weekends though) I appreciate what you do here. Helped me not only with certain procedures but you explain it to the why people like myself that like to "get it" the first time.
Oddly, I believe I am dealing with the same issue on a 2001 Toyota 4runner. Idles like a champ-sounds beautiful. Then you get out of the driveway and 10 to 20 miles an hour, can't get above 1800 rpm. Exhaust is wimpy and very hot at idle. A while back I had to replace the turbo on my lady friend's Subaru and while I was doing it, I came across a mention that when the turbo goes out, it dumps a lot of oil into the catalytic converter and plugs it up. I took it out and sure enough, filled with sticky, nasty carbon gunk. New cat, oil changes every 500 miles for the first three thousand miles and 20,000 miles later it is still running like a champ. Now, back to the 4runner-time to order cats--dagnabbit.
I see the references in the "Information" icon. Thanks, that helps. Ivan will be proud of your math skills and the display of his Pine Hollow shirt was a class act. I appreciate that you thought to make a video. As you know, I'm a sponge for learning this stuff and videos like yours sure helps! Plus you crack me up with your sense of humor. See you on the next one and thanks for the help on my truck. My wife is very happy to have "her" truck back, I thought it was mine but whatever. lol
It's easier to take off the digital EGR valve on GMs and use an adapter plate for back pressure tests. Better than risking breaking an O2 off in the manifold. You can make an adapter pretty easy out of a small piece of aluminum plate. Drill and tap the center hole for whatever size fitting you use on your gauge. You can use the gasket to lay out the hole pattern.
Great way to go from a hunch to proving it with a systematic approach to troubleshooting. You’re a great mechanic-Thanks for sharing your experience 👍🏻
Seems to me that the old school vacuum pressure gauge test....is quicker and easier to find the problem. Which as being the old coot that I am.....is very encouraging
Jerry is Jodie's cousin for the record😂 Discovered your channel while researching testing procedures for Exhaust Backpressure Sensor on 6.0 Powerstroke. I'm learning how to use my new scan tool and this will be my 1st attempt at setting up the scope. Matco Maximus 4.0. Replaced sensor (OEM), pigtail & tube couple of mths ago. Not sure if I may have disrupted something with the MAP sensor as I rebuilt the fuel injectors on that side last week and now this. I should've replaced the vacuum line when I noticed how stiff it was. Enjoyed watching you thoroughly test your hypothesis.
I've had several V8 Fords (460 cu in) that had the wrong cat on the vehicle. The cat(s) were plugged. This was pre pressure transducers. The old vacuum gauge at the intake manifold port, start the engine, good vacuum reading at sea level, 20 inches, until reved. WOW! Literally, the gauge went to zero within 10 seconds, shutting off the engine! Disconnected the "Y" pipe at the cat, STRONG RUNNING ENGINE! Just another way to test.
I have an adapter that threads into the O2 hole for a vacuum/pressure tap. Intake vacuum will show restricted exhaust as well, if it can’t get air out, it take air in. All your vids are popping up since I subbed. :)
Could you hook Ivan's pressure transducer up to the line that you had running to the front O2 bung? It would be neat to see a plot of the pressure there instead of just looking at the bouncy needle. It would also be good to confirm/calibrate the transducer output before using it by hooking an air chuck adapter to it and testing the pressure of car and truck tires that were inflated to known values. Chris
Nice case study! Look at my FB answer on your SMA page @1AM and my @9AM one. The 2 things that jumped out at me was when the exhaust valve opened prior to BDC the pressure immediately increased which normally it will continue to drop until after BDC and the piston is just starting it's exhaust stroke and the other was when the intake valve opened pressure dropped like normal but then immediately rose back up until the exhaust valve closed when normally the pressure would drop after the intake valve opened due to intake vacuum prior to it starting on the intake stroke BUT being supercharged the intake pressure would change the waveform to a less pronounced drop & being supercharged it just keep throwing the beans to it. What failed on the original engine & it had to be getting HOT & knocking like crazy?...How bad did it go BOOM? Snap-on has a new adapter that comes with their vacuum/pressure tester that has 2 different adapter threads & the hole is @1/4" to dampen pressure pulses. Nice transducer from Ivan! As usual great video & another satisfied SMA customer!
Just had a GMC Savana with the same problem, idles great, but no beans when you get on it. The van had just had a distributor replaced so initially thought timing was off, not the problem, took the O2 sensor out, gave her some beans and had lots of give, easy way to test for plugged Cat.
Thanks, very informative. That pressure transducer is a really cool tool. The cause of the high pressure would be good to know, I'd guess a clogged cat. Another reason that babying your car is just no good. You're asking for stuck rings and the resulting oil consumption, or this. This (if it is a clogged cat) is unusual, but the cat does require heat to function, and I suspect that many short and/or easy trips reduce catalyst life. I make sure I always get on it a few times- good for my car, and for me, too. That exhaust valve opening is probably at about 40 degrees before bottom dead center, rather than at it. Thanks for your informative and entertaining videos!
I recognised that engine - exact same I expect as the Holden Commodore 3.8L V6 Supercharged - of course in the Commodore it's pointing the right way with the pulleys at the front and driving the correct (rear!) wheels ;-)
Back pressure is never your friend. It's always your enemy. The ideal setup is a straight pipe with no cat or muffler... while that's typically illegal to drive on the streets (and loud as hellfire), it's absolutely ideal for perfect flow and no volumetric reflection or power robbing back pressure.
There may be exceptions. Consider this: I bought a used CJ5 Jeep that looked good, with a strong engine (304 v8) and a suprisingly low price. It was all good until I got onto a steep off road hill in 4wd low and instead of climbing the hill it hopped like a rabbit as the tires would slip with any throttle at all. The engine had too much power! I replaced it's after market headers and mufflers (cherry bombs) with a stock single muffler (to get some back pressure) and 4wd worked like it was supposed too. The gearing was matched to the horse power which was influenced by the back pressure. I hated to lose the cherry bombs. They were pretty.
I have this engine on a 95 Riviera. I got a lean code. Turned out to be a blown supercharger gasket that was found with a smoke test. Early ones had an awful accessory bracket covering the water pump and the SC snout. I think they built the engine around the water pump. Snout couplers rattle on these. I replaced mine a while back.
the fact that you didn;t trust your data is what makes you such a great mechanic! I'm having an issue I wish you could deal with right now honestly p0420 I cant afford cats and am hoping it is o2 sensors but I don't have a scan tool to do any testing. I could use the temp test but I have one of the chevy 2.4 motors with the oil burning issue and had that fixed by top end rebuild a year or so ago but the car has been fine till today.
Where can I buy this pressure transducer? The link for tools and toys is not working. Also great video and your not the only one that didn't trust the results of it. The in cylinder pressure testing is the future of engine performance mechanical diagnostics and even tho you didn't really know why you made the video it for sure helped me gain a little more experience with a known plugged exhaust. Thanks Richard White, shop Owner/Technician
I'm old school, if you think you have a restricted exhaust, raise up on hoist tap test converters check for noise. If you think firebrick is plugged with oil and soot, disconnect header pipe and run engine.....
When exhaust from the pipe wouldn't blow out a birthday candle; rearranging the spark plug wires during half time and petroleum jelly on the wipers could make for a long ride home. Backfiring through the muffler usually blew it to small pieces so the back pressure returned to normal. The un-burned gas left in the exhaust was used to help keep the valves at a lower operating temperature.
love your channel. should be studying for my mechanic final exam but been bindge watching your chanel. quick question. whats the best way to drop the engine quickly with the 3.8s? last one took me a good while. didnt help that the motor was locked up and getting the torque converter to flexplate bolts was a nightmare. drop the subframe im guessing ?
Has anyone simply tried a tire pressure gauge and an air compressor? You pick a cylinder with an open exhaust valve and pressurise it and read what the gauge gets to. Anything higher than atmospheric and the exhaust is blocked.
The only problem is, if any other cylinder has even a slightly cracked exhaust valve. Your reading is out the window. It would work on a single cylinder engine. We're talking multi cylinder engines. To be sure you'll have to pull the valve covers.
@@anomamos9095 sorry I didn't mean to confuse you by the turm " craked valve". I should have stated, if any other exhaust valve is slightly open at the time you pressurized your test cylinder, the air would go into an other cylinder , giving you an inaccurate pressure test for a plugged exhaust system. You would have to verify all exhaust valves are completely closed and sealed at the time of test... But I do like the way you think!
I would speculate that the rubber hose on the O2 sensor port was getting heated from the exhaust, causing the reading to fall over time. Very interesting piece. Thanks!
Hey Mr. O Its Mr. M. again. Just was watching some of your older videos and you asked the question of WHOS JERRY? Well its a slang term for GERMAN so its actually GERRY RIGGING. My family comes from Germany and my grandfather told me that a long time ago. Anywho as always love the videos and keep em coming. Say hi to Mrs O From Me and Mrs M.
Another indication or way to find out with boosted vehicles, On these Regals if you bring up the boost gauge on the cluster, it would give you a quick indication when you go into positive intake pressure, it would shoot up over the stock 8-10 psi under load, usually under part throttle to WOT and show you about the same results and fault.
Awesome testing, Eric! Cool to see my psi transducer in action! Now I'm wondering how you saw 7V on that...did I give you Version 1.0 without a 5V regulator? One note that someone brought up in one of ScannerDanner's vids is that the in cylinder pressure during the exhaust stroke will always be higher than at the O2 sensor since the exhaust valve orifice acts as a restriction. Try a snap throttle on a known-good vehicle and you will see what I mean. Don't wanna get slid by trusting your data blindly! Kudos for using two methods to confirm the diagnosis. A true scientist!
Yes sir this is the OG 1.0 no regulator just straight hard core haha. It is funny you mention that because the whole night I was thinking... why was that different! Then about 3am I awoke and smiled because it finally hit me :)
Oh man science experiments are keeping you up at night huh? Well you might as well keep it simple if it works; with a 5V reg it would top out at 175psi unless you upgraded to a higher range transducer!
HI Eric, Nice testing method,, I had a Buddys GTP 3800 sc with a clogged Cayt,, so bad it tore the tubular exhaust manifold open , Banged it back together and mig welded it closed ,, wonder what kind of back pressure he had ,,
Pretty cool Eric , I always see it used on in cylinder testing , not much on fuel pressure testing. I would think direct injection engines would need to be tested with a transducer , ha I don't know just guessing. Cheers buddy...
Seems like the “hose effect” might be more from the expansion of the rubber hose absorbing / dampening the pressure before it gets to your gauge. What do you think?
Hey Eric, with a huge blockage like that would you be able to recognize the blockage by putting your hand kinda over the exhaust at the rear of the car and having someone hit the throttle?
Thank you- Do you happen to know what the maximum sample rate of that transducer is? I was curious just how fast of pressure measurement I could take with something similar. It's two stroke over 10k rpm wanting it to be able to at least sample every crank degree. I'm new to this but id assume I'd need a sensor at least 60khz? Didn't know if that even exists
Man with all that back pressure that charger sounds like it has been pullied down and ported out..HAHA. Gradma's got boost! Interestingly enough, those 3800's need a little bit of back pressure to run well. The butt-dyno in our cicrles ( i am a 3800 nut) says that doing a cat removal loses HP. Thanks for the video Dr. O
awesome video Man. Your channel, Scanner Danner and motoyam are the best. I learn some new tricks all the time watching you guys videos. keep up the good work! How do you like the autel maxiscope? I have the auto maxisys mini and it's great but i can't bring myself to pull the trigger on the scope.
Wow 70 Pounds Of Back Pressure that is impressive it even runs or idles pretty strong motor For sure Eric O good Video very informative @SouthMainAutoRepairLLC
Cool . I still have my old snap on counselor 2 Vac transducer I've used it to test compression problems. Now i need to find out how it works on back psi. Also Got me thinking. The map sensor volts I think would have been high right?
Remember being super charged the MAP is a bit different than a NA engine. We deal with negative and positive manifold pressures. At an idle I would have to believe we could have saw that though. Counselor II!? Man thought I was th only one to have one of those haha
Eric, it's "Jury Rigged" or "Jerry Built". A Jury Rig is an emergency sailboat rig if the mast has come down. Jerry Built refers to a poor firm of 19th century builders in Liverpool UK. So Jerry is off the hook! Greg (UK)
When you’re calculating the back pressure you are taking the voltage 7.2 deducting 1/2 a volt and multiplying by 40. How does the half volt and x 40 come into play? Where do those numbers come from? Great videos thanks for all the effort.
0.5V is atmospheric pressure, that's what the transducer is showing when nothing is affecting it other than the atmosphere. Multiplying by 40 is because that transducer is 40 PSI per V. He explained all of this in the video btw, although maybe not directly.
BDC occurs before the point at 28.5 ms you noted on the o-scope. At 10:00 you put cursor at time peak to peak divided by 4 or at 28.5 ms and said its BDC. But...it was at 501 mv or the average level of the exhaust pressure trace section. Problem with that is, about 5/8 of a div before that point or what would be 27.25 ms we see pressure hit a low then rise up to about atmo at 28.5 ms. The piston can't just have hit BDC at 28.5 if pressure is rising between 27.25 and 28.5 ms. BDC was actually hit at the low point of the curve about 5/8 of a div or at 27.25 ms before the 28.5 ms point you noted. At 28.5 ms the valve is nearly or already fully open. The valve started opening at 27.25 ms because pressure starts rising right after that. I thought perhaps the piston may be rising but we are not 1/4 way thru time and the valve should open/opening before piston rises. So BDC first occurs at 27.5 ms and the pressure rising at 27.5 ms is start of valve opening. At 28.5 ms I'd say thats where the exhaust stroke and piston physically rising starts, not where BDC occurs albeit the piston may still be at BDC then. Don't mean to be anal here, it was strange to hear you say this is BDC and the scope shows pressure has already been rising, we think of BDC as the low point in pressure.It may have been between to say, this is start of exhaust stroke at 28.5 ms. Or......I could be completely wrong..................... Please don't shoot me I'm only the piano player. Your Navy Nuc Sub Veteran fan in internet world -Don
If you suspect a clogged cat, remove the front oxygen sensor. It will be very noisy, but if it runs better (and it should run a LOT better if the cat is clogged), you have an exhaust restriction.
Did you get the job to fix it? If so, what was the restriction? I had a plugged catalytic converter on my 2005 T&C van and it didn't show up until we loaded the van and went on vacation and had trouble getting up hills. I had gotten a P420 code a couple times in previous months, but thought it was from driving through snow or a minor cat issue. My wife had no trouble around town, but it wouldn't go above 60 on a hill. I have a video showing the symptoms I had. Had to get it replaced on vacation, but it solved the problem.
Whoa. Personally I hate trying to remove an o2 sensor to hook up a back pressure gauge. In NY that's easier said than done. I also don't drill holes in the exhaust either, I suppose it wouldn't hurt if you plugged it back up. But yeah, I will try it your way now. thanks for sharing.
did the high back pressure blow past the rings and blow the oil out the old block ? I'm surprised it didn't kill the valve gear - did you get a quick vid or pic of the blocked cat ?
3800 is notorious for knocking if conditions aren't right. The stock exhaust was designed horribly and is way too restrictive. Removing the u-bend just before the resonator deletes a good chunk of knock. Actually, upgrading to headers is the #1 way to eleminate knock on these motors (besides intercooling). I don't think there is much hope for the engine at this point. You should hook up the Snap-On scan tool and see what value of KR comes up. It should have less than 1 degree lol.
Your ability to break down complex concepts into understandable (and often hilarious) terms never ceases to amaze me. I've learned so much from these videos - not just about automotive issues but about the troubleshooting process in general. Thanks for the time you put into these!
In a Buick I worked on 40 years ago I had a similar situation. The car ran fine at idle... but as the load and speed went up the engine bogged badly. The problem was a collapsed exhaust pipe. Not that you could see any deformation the outside .. but the pipe delaminated and one layer collapsed and choked off the inside. I couldn't believe it until I sawed it open. Replaced the pipe and all was well. Kept that pipe on the wall for years.
Phil
Laminated exhaust pipe?
Phil Kohl I had the same happen long time ago.
GM used a double wall exhaust pipe on many vehicles from 1969 to 1973. If you were driving with a hot exhaust pipe [ high speed cruising for example ] and went thru a large puddle of water, the cold water would hit the exhaust pipe, then the inner pipe layer would collapse and block the exhaust flow. You had to cut the pipe open to see it most of the time as it would do this near the middle of the length of the exhaust pipe. I saw this on a Bonneville and an El Camino..
Sounds like a problem you’d see in a cast iron plumbing pipe which will “delaminate” over time. Went to put a pipe plug in once and couldn’t get any to fit. Even chipping some away
I'm waiting for you to get ahold of an old 70's, 80's model without all the high tech computers involved. All your "gadgets" are over my head. Love It.
The 3800, best V6 ever created. I miss mine already. Small, light powerful and can be swapped out in four hours. A thing of beauty is a joy forever. With the supercharger this thing was fast as well.
What i really wanted to see was what was plugging the exhaust.
i'm just a diy, driveway joe, i find this kind of stuff absolutely fascinating. way beyond my skill set, another gr8 video from SMA ,,Thx Eric O
23:44 I need to see this video it really helped me with my problems with my 2002 Chevy Silverado I could not figure out what was going on with my truck until I saw this video. I had the same problem with my exhaust stopped up
Another great video. So glad you decided to make it once you saw the issue and its magnitude. I'd love to see a follow up that shows where the blockage was and the "after" readings.
IMHO you are too quick to beat yourself up. It was a good hypothesis, and you went through the steps to prove it. The easy stuff is easy, and if you have to get dragged through the mud a little bit to satisfy yourself on the hard ones, that's okay.
Every decision you (or anybody) make is done with consideration of the cost associated, based on previous experience. This didn't strike me as too high of a cost to really get a solid diagnosis. Sure it's a bit of time spent, but that time spent will yield positive results for you (and now me) in the future, so it was time spent but not time wasted.
Once again, thank you.
4 years ago... And still relevant! Nice episode!
You the man Eric nothing like watching a real pro do his job. Not many mechanics like you anymore really wish you worked in Maine you would have a new customer. Keep up the great work! Really enjoy your videos watch them daily!
I watched a couple of guys do these bad cat bad flow video's on different cars... the performance varies a lot... i am 99 % sure i have this issue and possibly i installed my distributor in a tooth off because it used to be drivable and idle like a kitten...but when i drove it ..it lacked half its horse power bucked and hesitated intermittently... thax for all your great repair video's...
hey Erick.I have been watching your videos and noticed that in every other video you have different scan tools. and was wondering if you could make a video comparing the different scan tools. thanks for sharing your knowledge.
You guys want a good laugh turn on the self generated captions on this and watch it again. Love the videos keep up the good work, (not on weekends though) I appreciate what you do here. Helped me not only with certain procedures but you explain it to the why people like myself that like to "get it" the first time.
Eric, great video, great to learn multiple methods of diagnostic testing to verify a suspected failed component!!
Eric you should make up some hats or shirts from SMA with “there’s your problem lady” I would definitely buy one and I’m sure others would too!
So awesome of ivan to make you a Pressure Transducer Eric O @3:20 @SouthMainAutoRepairLLC
Are you going to show where the blockage was,CAT,crushed pipe,muffler?
I'd be keen to see this too
Every so often I hear "Welcome to the self made auto channel" and I think, "Yes it is". Then I remember you are saying South Main..lol
It does not hurt to double check one method with another if something weird is happening. You did it again Eric, THANKS FRIEND
Oddly, I believe I am dealing with the same issue on a 2001 Toyota 4runner. Idles like a champ-sounds beautiful. Then you get out of the driveway and 10 to 20 miles an hour, can't get above 1800 rpm. Exhaust is wimpy and very hot at idle. A while back I had to replace the turbo on my lady friend's Subaru and while I was doing it, I came across a mention that when the turbo goes out, it dumps a lot of oil into the catalytic converter and plugs it up. I took it out and sure enough, filled with sticky, nasty carbon gunk. New cat, oil changes every 500 miles for the first three thousand miles and 20,000 miles later it is still running like a champ. Now, back to the 4runner-time to order cats--dagnabbit.
Best constipation video I've seen with exception of that 4 banger frontier from nissan
I see the references in the "Information" icon. Thanks, that helps. Ivan will be proud of your math skills and the display of his Pine Hollow shirt was a class act. I appreciate that you thought to make a video. As you know, I'm a sponge for learning this stuff and videos like yours sure helps! Plus you crack me up with your sense of humor. See you on the next one and thanks for the help on my truck. My wife is very happy to have "her" truck back, I thought it was mine but whatever. lol
It's easier to take off the digital EGR valve on GMs and use an adapter plate for back pressure tests. Better than risking breaking an O2 off in the manifold. You can make an adapter pretty easy out of a small piece of aluminum plate. Drill and tap the center hole for whatever size fitting you use on your gauge.
You can use the gasket to lay out the hole pattern.
A naturally aspirated engine probably would never be able to create that much back pressure. This is definitely a special case. Good work.
Great way to go from a hunch to proving it with a systematic approach to troubleshooting. You’re a great mechanic-Thanks for sharing your experience 👍🏻
Seems to me that the old school vacuum pressure gauge test....is quicker and easier to find the problem. Which as being the old coot that I am.....is very encouraging
Jerry is Jodie's cousin for the record😂 Discovered your channel while researching testing procedures for Exhaust Backpressure Sensor on 6.0 Powerstroke. I'm learning how to use my new scan tool and this will be my 1st attempt at setting up the scope. Matco Maximus 4.0. Replaced sensor (OEM), pigtail & tube couple of mths ago. Not sure if I may have disrupted something with the MAP sensor as I rebuilt the fuel injectors on that side last week and now this. I should've replaced the vacuum line when I noticed how stiff it was. Enjoyed watching you thoroughly test your hypothesis.
I learn so much from every video. Sure appreciate you taking the time to post this stuff.
Cool. Eric sporting the PHAD shirt.
I've had several V8 Fords (460 cu in) that had the wrong cat on the vehicle. The cat(s) were plugged. This was pre pressure transducers. The old vacuum gauge at the intake manifold port, start the engine, good vacuum reading at sea level, 20 inches, until reved. WOW! Literally, the gauge went to zero within 10 seconds, shutting off the engine!
Disconnected the "Y" pipe at the cat, STRONG RUNNING ENGINE!
Just another way to test.
I have an adapter that threads into the O2 hole for a vacuum/pressure tap. Intake vacuum will show restricted exhaust as well, if it can’t get air out, it take air in.
All your vids are popping up since I subbed. :)
Could you hook Ivan's pressure transducer up to the line that you had running to the front O2 bung? It would be neat to see a plot of the pressure there instead of just looking at the bouncy needle. It would also be good to confirm/calibrate the transducer output before using it by hooking an air chuck adapter to it and testing the pressure of car and truck tires that were inflated to known values. Chris
Nice case study! Look at my FB answer on your SMA page @1AM and my @9AM one. The 2 things that jumped out at me was when the exhaust valve opened prior to BDC the pressure immediately increased which normally it will continue to drop until after BDC and the piston is just starting it's exhaust stroke and the other was when the intake valve opened pressure dropped like normal but then immediately rose back up until the exhaust valve closed when normally the pressure would drop after the intake valve opened due to intake vacuum prior to it starting on the intake stroke BUT being supercharged the intake pressure would change the waveform to a less pronounced drop & being supercharged it just keep throwing the beans to it. What failed on the original engine & it had to be getting HOT & knocking like crazy?...How bad did it go BOOM? Snap-on has a new adapter that comes with their vacuum/pressure tester that has 2 different adapter threads & the hole is @1/4" to dampen pressure pulses. Nice transducer from Ivan! As usual great video & another satisfied SMA customer!
Just had a GMC Savana with the same problem, idles great, but no beans when you get on it. The van had just had a distributor replaced so initially thought timing was off, not the problem, took the O2 sensor out, gave her some beans and had lots of give, easy way to test for plugged Cat.
Thanks, very informative. That pressure transducer is a really cool tool.
The cause of the high pressure would be good to know, I'd guess a clogged cat.
Another reason that babying your car is just no good. You're asking for stuck rings and the resulting oil consumption, or this. This (if it is a clogged cat) is unusual, but the cat does require heat to function, and I suspect that many short and/or easy trips reduce catalyst life.
I make sure I always get on it a few times- good for my car, and for me, too.
That exhaust valve opening is probably at about 40 degrees before bottom dead center, rather than at it.
Thanks for your informative and entertaining videos!
I recognised that engine - exact same I expect as the Holden Commodore 3.8L V6 Supercharged - of course in the Commodore it's pointing the right way with the pulleys at the front and driving the correct (rear!) wheels ;-)
Holden is Australian
love the 3800 supercharged engines definitely fun in my GTP I had
good lesson eric..wouldnt a clogged exhaust make it overheat from just running at idle?
Jerry-Rigged comes from an old english sailing term "jory saile" which means a make shift sail/rigging setup on a ship.
Good video and very good use of the pressure transducer. You make Ivan sound like a mad scientist lol. You both do a very good job with your videos
Back pressure is never your friend. It's always your enemy. The ideal setup is a straight pipe with no cat or muffler... while that's typically illegal to drive on the streets (and loud as hellfire), it's absolutely ideal for perfect flow and no volumetric reflection or power robbing back pressure.
There may be exceptions. Consider this: I bought a used CJ5 Jeep that looked good, with a strong engine (304 v8) and a suprisingly low price. It was all good until I got onto a steep off road hill in 4wd low and instead of climbing the hill it hopped like a rabbit as the tires would slip with any throttle at all. The engine had too much power! I replaced it's after market headers and mufflers (cherry bombs) with a stock single muffler (to get some back pressure) and 4wd worked like it was supposed too. The gearing was matched to the horse power which was influenced by the back pressure. I hated to lose the cherry bombs. They were pretty.
I thank you very much for sharing your knowledge on demostraiting on how to used the EScope t diagnost a plug converter. Thank you.
i had one that was 8 psi at idle and still ran. gotta love the w body.
Hey thanks for sharing the find with us...excellent ..
good video, thanks, can you share the site on how to make that pressure transducer please, thank you again
Enjoyed the vid Eric. Nice comparison between the mechanical and digital data.
Hey Eric, my birthday is in 2 days. And a birthday wish from you would be great! Love your videos.
i understanded the backpressure test perfectly on the scope now!
I have this engine on a 95 Riviera. I got a lean code. Turned out to be a blown supercharger gasket that was found with a smoke test. Early ones had an awful accessory bracket covering the water pump and the SC snout. I think they built the engine around the water pump. Snout couplers rattle on these. I replaced mine a while back.
Your right as you told me that this video would be interesting and you were right. And I forgot to ask when at SMA, what was plugged?
the fact that you didn;t trust your data is what makes you such a great mechanic! I'm having an issue I wish you could deal with right now honestly p0420 I cant afford cats and am hoping it is o2 sensors but I don't have a scan tool to do any testing. I could use the temp test but I have one of the chevy 2.4 motors with the oil burning issue and had that fixed by top end rebuild a year or so ago but the car has been fine till today.
Loving the crickets in the background
Where can I buy this pressure transducer? The link for tools and toys is not working. Also great video and your not the only one that didn't trust the results of it. The in cylinder pressure testing is the future of engine performance mechanical diagnostics and even tho you didn't really know why you made the video it for sure helped me gain a little more experience with a known plugged exhaust. Thanks Richard White, shop Owner/Technician
I'm old school, if you think you have a restricted exhaust, raise up on hoist tap test converters check for noise. If you think firebrick is plugged with oil and soot, disconnect header pipe and run engine.....
When exhaust from the pipe wouldn't blow out a birthday candle; rearranging the spark plug wires during half time and petroleum jelly on the wipers could make for a long ride home. Backfiring through the muffler usually blew it to small pieces so the back pressure returned to normal. The un-burned gas left in the exhaust was used to help keep the valves at a lower operating temperature.
That was so interesting. Fantastic video Mr owe
Could you have used a temperature reading using Non-contact Digital Laser Infrared Thermometer at the cat to confirm the symptoms?
love your channel. should be studying for my mechanic final exam but been bindge watching your chanel.
quick question. whats the best way to drop the engine quickly with the 3.8s? last one took me a good while. didnt help that the motor was locked up and getting the torque converter to flexplate bolts was a nightmare.
drop the subframe im guessing ?
Cool video. Its hard to believe that backpressure was so high.
Has anyone simply tried a tire pressure gauge and an air compressor? You pick a cylinder with an open exhaust valve and pressurise it and read what the gauge gets to. Anything higher than atmospheric and the exhaust is blocked.
I like your idea boss
@@waynemoore5259 Problem with that is that engines flow an awful amount of air. Regular shop air won't do much there.
The only problem is, if any other cylinder has even a slightly cracked exhaust valve. Your reading is out the window. It would work on a single cylinder engine. We're talking multi cylinder engines. To be sure you'll have to pull the valve covers.
@@daveschidlmeier6425 . As the test is for a blocked exhaust system a bad valve would be a different problem.
@@anomamos9095 sorry I didn't mean to confuse you by the turm " craked valve". I should have stated, if any other exhaust valve is slightly open at the time you pressurized your test cylinder, the air would go into an other cylinder , giving you an inaccurate pressure test for a plugged exhaust system. You would have to verify all exhaust valves are completely closed and sealed at the time of test... But I do like the way you think!
I would speculate that the rubber hose on the O2 sensor port was getting heated from the exhaust, causing the reading to fall over time. Very interesting piece. Thanks!
Excellent tutorial Eric O
Hey Mr. O Its Mr. M. again. Just was watching some of your older videos and you asked the question of WHOS JERRY? Well its a slang term for GERMAN so its actually GERRY RIGGING. My family comes from Germany and my grandfather told me that a long time ago. Anywho as always love the videos and keep em coming. Say hi to Mrs O From Me and Mrs M.
Another indication or way to find out with boosted vehicles, On these Regals if you bring up the boost gauge on the cluster, it would give you a quick indication when you go into positive intake pressure, it would shoot up over the stock 8-10 psi under load, usually under part throttle to WOT and show you about the same results and fault.
Awesome testing, Eric! Cool to see my psi transducer in action! Now I'm wondering how you saw 7V on that...did I give you Version 1.0 without a 5V regulator?
One note that someone brought up in one of ScannerDanner's vids is that the in cylinder pressure during the exhaust stroke will always be higher than at the O2 sensor since the exhaust valve orifice acts as a restriction. Try a snap throttle on a known-good vehicle and you will see what I mean.
Don't wanna get slid by trusting your data blindly! Kudos for using two methods to confirm the diagnosis. A true scientist!
Yes sir this is the OG 1.0 no regulator just straight hard core haha. It is funny you mention that because the whole night I was thinking... why was that different! Then about 3am I awoke and smiled because it finally hit me :)
Oh man science experiments are keeping you up at night huh? Well you might as well keep it simple if it works; with a 5V reg it would top out at 175psi unless you upgraded to a higher range transducer!
+motoYam82
you should do a video on pressure transducers or a how build one and the science behind it
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Jerry was the German soldier back in WW 2
Great video.
HI Eric, Nice testing method,, I had a Buddys GTP 3800 sc with a clogged Cayt,, so bad it tore the tubular exhaust manifold open , Banged it back together and mig welded it closed ,, wonder what kind of back pressure he had ,,
Pretty cool Eric , I always see it used on in cylinder testing , not much on fuel pressure testing. I would think direct injection engines would need to be tested with a transducer , ha I don't know just guessing. Cheers buddy...
Great analysis man
Seems like the “hose effect” might be more from the expansion of the rubber hose absorbing / dampening the pressure before it gets to your gauge. What do you think?
Well at least you knew all the exhaust gaskets were tight!
That was awesome I have never seen a reading that high
Eric, just to let you know since ya asked, Jerry is Wills best friend, That poor bugger that everyone is firing at { : Love Your Work!
Thank You { :
Hey Eric, with a huge blockage like that would you be able to recognize the blockage by putting your hand kinda over the exhaust at the rear of the car and having someone hit the throttle?
I could watch all night
Thank you-
Do you happen to know what the maximum sample rate of that transducer is? I was curious just how fast of pressure measurement I could take with something similar. It's two stroke over 10k rpm wanting it to be able to at least sample every crank degree. I'm new to this but id assume I'd need a sensor at least 60khz? Didn't know if that even exists
Man with all that back pressure that charger sounds like it has been pullied down and ported out..HAHA. Gradma's got boost! Interestingly enough, those 3800's need a little bit of back pressure to run well. The butt-dyno in our cicrles ( i am a 3800 nut) says that doing a cat removal loses HP. Thanks for the video Dr. O
awesome video Man. Your channel, Scanner Danner and motoyam are the best. I learn some new tricks all the time watching you guys videos. keep up the good work!
How do you like the autel maxiscope? I have the auto maxisys mini and it's great but i can't bring myself to pull the trigger on the scope.
20:44 wank means something completely different in Britain 😂
Wow 70 Pounds Of Back Pressure that is impressive it even runs or idles pretty strong motor For sure Eric O good Video very informative @SouthMainAutoRepairLLC
Wow finally somebody with an Autel Scope
Cool . I still have my old snap on counselor 2 Vac transducer I've used it to test compression problems. Now i need to find out how it works on back psi. Also Got me thinking. The map sensor volts I think would have been high right?
Remember being super charged the MAP is a bit different than a NA engine. We deal with negative and positive manifold pressures. At an idle I would have to believe we could have saw that though. Counselor II!? Man thought I was th only one to have one of those haha
Nice, I'm like you. I keep old tools. You never know when you might need it. See you soon.
Eric, it's "Jury Rigged" or "Jerry Built".
A Jury Rig is an emergency sailboat rig if the mast has come down. Jerry Built refers to a poor firm of 19th century builders in Liverpool UK.
So Jerry is off the hook!
Greg (UK)
So helpful! Very good video
Thanks for the new vids Mr O. We are like crackheads. No going back now. 😎
When you’re calculating the back pressure you are taking the voltage 7.2 deducting 1/2 a volt and multiplying by 40. How does the half volt and x 40 come into play? Where do those numbers come from? Great videos thanks for all the effort.
0.5V is atmospheric pressure, that's what the transducer is showing when nothing is affecting it other than the atmosphere. Multiplying by 40 is because that transducer is 40 PSI per V.
He explained all of this in the video btw, although maybe not directly.
And you look good there Dr O sporting that PHAD shirt!
I can tell you love your electronic toys.
BDC occurs before the point at 28.5 ms you noted on the o-scope. At 10:00 you put cursor at time peak to peak divided by 4 or at 28.5 ms and said its BDC. But...it was at 501 mv or the average level of the exhaust pressure trace section. Problem with that is, about 5/8 of a div before that point or what would be 27.25 ms we see pressure hit a low then rise up to about atmo at 28.5 ms.
The piston can't just have hit BDC at 28.5 if pressure is rising between 27.25 and 28.5 ms. BDC was actually hit at the low point of the curve about 5/8 of a div or at 27.25 ms before the 28.5 ms point you noted.
At 28.5 ms the valve is nearly or already fully open. The valve started opening at 27.25 ms because pressure starts rising right after that. I thought perhaps the piston may be rising but we are not 1/4 way thru time and the valve should open/opening before piston rises.
So BDC first occurs at 27.5 ms and the pressure rising at 27.5 ms is start of valve opening. At 28.5 ms I'd say thats where the exhaust stroke and piston physically rising starts, not where BDC occurs albeit the piston may still be at BDC then.
Don't mean to be anal here, it was strange to hear you say this is BDC and the scope shows pressure has already been rising, we think of BDC as the low point in pressure.It may have been between to say, this is start of exhaust stroke at 28.5 ms.
Or......I could be completely wrong.....................
Please don't shoot me I'm only the piano player.
Your Navy Nuc Sub Veteran fan in internet world -Don
You.The.Man. YeSir...
If you suspect a clogged cat, remove the front oxygen sensor. It will be very noisy, but if it runs better (and it should run a LOT better if the cat is clogged), you have an exhaust restriction.
Did you get the job to fix it? If so, what was the restriction? I had a plugged catalytic converter on my 2005 T&C van and it didn't show up until we loaded the van and went on vacation and had trouble getting up hills. I had gotten a P420 code a couple times in previous months, but thought it was from driving through snow or a minor cat issue. My wife had no trouble around town, but it wouldn't go above 60 on a hill. I have a video showing the symptoms I had. Had to get it replaced on vacation, but it solved the problem.
th-cam.com/video/jPlifvgyrVI/w-d-xo.html
Whoa. Personally I hate trying to remove an o2 sensor to hook up a back pressure gauge. In NY that's easier said than done. I also don't drill holes in the exhaust either, I suppose it wouldn't hurt if you plugged it back up. But yeah, I will try it your way now. thanks for sharing.
did the high back pressure blow past the rings and blow the oil out the old block ? I'm surprised it didn't kill the valve gear - did you get a quick vid or pic of the blocked cat ?
3800 is notorious for knocking if conditions aren't right. The stock exhaust was designed horribly and is way too restrictive. Removing the u-bend just before the resonator deletes a good chunk of knock. Actually, upgrading to headers is the #1 way to eleminate knock on these motors (besides intercooling). I don't think there is much hope for the engine at this point.
You should hook up the Snap-On scan tool and see what value of KR comes up. It should have less than 1 degree lol.
Keep the videos coming, great case history !
great video I didn't no u could use your fuel pressure gauge for that and does Ivan sell them to anyone
"Look, man, I ain't fallin' for no banana in my tailpipe!"
Where was it plugged and what did you change? Also how to determine where it is plugged.