ScannerDanner – How to test for a plugged exhaust (picoscope & psi transducer)

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36 Responses

  1. Part 2 of this video will be available only on ScannerDanner Premium.
    Don't worry, if you are not a subscriber, there is no cliff hanger at the end of this video. I promise you will learn something even without the Part 2 video.
    In part 2, I discuss the variables with my friend Mr. Kaplan and then we drill holes in the exhaust in various locations to prove where exactly the restrictions are. We are very surprised by what we find. 

  2. rhkips says:

    Hmm, very interesting!  Out of curiosity, are the compression stroke numbers normal for a running engine?  I was seeing 60-75 PSI at peak compression on your scope there, which is about half of what I would expect to see doing a cranking compression test.  Having never analyzed a running engine before, I'm curious if this is a normal number, or if it's another sign of a restricted exhaust (can't exhale, can't inhale).

  3. This test you can do same. any vehicle.sorry for my bad English

  4. Just a question.
    Can you tell me why an unconneceted plug wire can overload the ignition coil while the engine is running?

  5. Tom N says:

    Fantastic as always.

  6. Nick Nicu says:

    Paul,I have a question regarding your preliminary conclusion that directed you towards a plugged exhaust : you look at the O2s on each bank at WOT and see they are rich,thus eliminating the dirty MAF possibility. My confusion comes because I thought at WOT the fuel trims go in OPEN loop and the computer is not using O2 readings. Do you record those 800mV readings right before it goes in OPEN loop?

  7. 1quickchevy2 says:

    Part 2 says it's not available in my country (Canada) and I'm a subscriber

  8. contagiousFX says:

    checking backpressure test on the dpfe line can bite you later because it's not 100% accurate.

  9. Tim Moss says:

    Paul , i too have the "Unable to view in your country" message but i think it's purely YouTube vetting the post before they release it for me to view . I think some others may come across this message also when trying to view it . 
    Like you say best thing to do if already subscribing is to give it 12-24 hrs and see if able to view there after .   Tim :)

  10. Tim Moss says:

    Haha  … just tried it one more time for luck , and i'm now able to watch it 😀  
    Literally 1 min between .

  11. James Brewer says:

    I got a 98 cadillac eldorado , Bank 2 is running 25 on Long term Bank 1 is running 5 on the long term. I thought it was the intake manifold cause i smoked it and some smoke leaked out of the intake. I replaced the intake gasket  and come to find out the smoke was coming out of a backfire "Flap" so i had no leak to begin with, while i was doing this i swapped the injectors from bank 2 to bank 1 and vise versa incase it was an injector issue. My o2 sensors seem to respond together when i introduce propane into the intake, i also checked for vac Leaks with water / propane and eltrical cleaner. and no change in shortterm/longterm. @ idle. The only other thing i can think of is that i have a exhaust manifold thats leaking , any insight would be greatly appriciated , Thanks

  12. are plugged exhaust systems that common? also how would you reccomend testing for this if you dont have a scope and the exhaust is super rusted?

  13. Mike Eustice says:

    Hey danner don't know if u showed this in part two but a vacuum gauge hooked to the intake could point to a plugged converter the reading on the gauge would be less vacuum at 2500 to 3000 rpm than at idle due to it not being able to breath 

  14. Mike Eustice says:

    Hey danner don't know if u showed this in part two but a vacuum gauge hooked to the intake could point to a plugged converter the reading on the gauge would be less vacuum at 2500 to 3000 rpm than at idle due to it not being able to breath 

  15. nevermind you answered the questions

  16. youre hooking me Danner now I must subscribe to the primo channel As my exhaust makes a whistle beyond 3000 rpm WOT Thanks for youre fine work Amigo.

  17. 02lowrider62 says:

    What scan tool are you using ? Sure don't look like your verus or am I wrong

  18. Thanks for this interesting analysis Paul; what about measuring the vacuum pressure from intake using the pico or even a pressure gauge to detect a plug exhaust?

  19. Tom Smith says:

    Hi Paul I had one that when you take it on a road test or revved it high the exhaust prior to the blocked exhaust glowed red hot if that's any help…what about looseneing flange coupling instead of drilling hole, to let pressure out Fred uk

  20. Ozzstar says:

    Another great video.  Thank you

  21. vessellsbuzz says:

    Paul, If the fuel trims are normal then the plugged cat is the rear one. This is because the MAF correctly measures the incoming air. Then the air is equally distributed bank to bank. If the fuel trims are negative on one bank and positive on the other bank the same amount. Example -22 total fuel trim on bank 1 and 22 total fuel trim on bank 2. Then only one bank is plugged. This is because the engine is now drawing in less air, due to one of the banks cat being plugged. The MAF reads the incoming air correctly, but then the unrestricted bank takes the majority of the air and the restricted side does not, but the fuel is still being added by the injectors on the restricted side. This means the restricted side is getting to much fuel for the amount of air it has available. This means the side with the negative fuel trims is the restricted bank. Hope this info helps.

  22. Hello Scanner,
    I purchased your E Book recently. I like it a lot, as it is an easy read.

    Question, do you have any suggestion for reducing noise using the PICO orange handle COP probe? I get a lot of noise on the screen. Any ideas?

    Do you think the new PICO scope is worth the upgrade?

    Thanks for what you do! 

  23. Hi Paul, great video. I have a WPS 500 and have not considered using for in cylinder back pressure testing as I normally drill a small hole & weld it later.
    One thing though, have you struck back pressure in the exhaust manifold (before the turbo)being higher than normal for turboed engines?
    What are your thoughts.
    New Zealand. 

  24. Paul,how you ever use  fuel trim as a guide direction for plug exhaust? a was in a class where the teacher said  for example if you have in  bank 1, 12 positive  and -12 on bank 2. classic  fuel trim numbers of plug exhaust  on  v type engines . Personally I have not seen it yet, but I hope I can get one soon.

  25. dmorley100 says:

    Yeah, I go with replacing all the cats too when there's 3 or more cats on a car myself. I learned that the hard way on a Hyundai Santa Fe.

  26. scannerdanner what is the best way to adjust a carb? i dont know this old stuff maybe you can help. its a carter series i think thats the same as an edelbrock. 

  27. bobl78 says:

    How many cats do US cars have ? Does it get better when they put in a dozend cats ? How about designing engines that have cleaner raw exhaust ?

  28. Adi Sinkopa says:

    ScannerDanner, my PRO virtual teacher, i really apreashiate all your great clips.
    i have a humble request: if you can do a video clip about the Accelerator Pedal Position Sensor.
    i realy have a tough time with it.
    thanks allot and god bless.
    Adi from israel.

  29. douglas lee says:

    This vid is definitely in the top 20% of your collection. Seeing the pressure pulsations to that level of detail and resolution is amazing. The moment you rev'd the engine on the first bank test I knew what the problem was (like you did). I don't have Premium, so I won't see the follow-up video.

    Also, in a shop environment, a tech could print a screen shot of that waveform and provide it to the customer, to show the proof that the exhaust is plugged. One of the many benefits of computerized testing.

    Knowing if the second bank tested has a bad cat would be a little tougher call, but fortunately both pre-cats get replaced together because they are all part of one Y pipe assembly as you said, so that fairly tough call on the second pre-cat isn't one that necessarily needs to be made.

    Even though this video would normally be in the Premium area only, I humbly suggest shooting a follow-up after the exhaust is fixed, so that those of us without Premium can still see what the outcome was.

    That pressure gauge is SWEET, but at 750 clams, not something I'll be buying in this lifetime (but for a Pro it would be worth it, but not for me as an amateur).

    By the way, my brother has a 1997 Ford F-150  4.6L V-8.  I removed the driver's side O2 to test for a plugged cat, because he has had a massive vacuum leak for a long time, (cracked intake manifold lower section-plastic-) along with massive lean misfires, but lots of fuel going through, because the computer is dumping in fuel, but can't bring the mixture into a combustible range. Anyway, the gauge measured only .1 to .2 psi of back pressure, even at higher rev's. It was your video's that explained proper exhaust back pressures that taught me how to do that, and to know the his cat's are OK.

    Thanks Paul

  30. douglas lee says:

    Nevermind…….I HAVE to learn to read all the comments before I post my own. I just saw the note that said the car was wrecked and the "after" vid would not be available. Bummer.

  31. 8power0 says:

     Another very good video , it shore would have been great to have seen one cylinder pressure transducer per bank at the same time and two firstlook engine diagnostic pulse sensors one at the intake manifold and the next one in the tailpipe, very advanced diagnostics and thank you again.

  32. Another good one. Can't forget to have the exhaust shop check the muffler for cat debris. Maybe you mentioned that in your part 2. Thanks again.

  33. muy bueno en español por favor un abrazo

  34. Cyril Buss says:

    Great Video.  That was really cool.

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