In this video I show how to use multiple methods in order to identify and pinpoint a specific misfire and then the root cause. The customer had replaced multiple items and was still left with a misfire on this 2007 MB S550
Even if you don't have a scope, manual compression and leakdown tests and a bore scope would have saved money for any parts thrown one might choose to toss at it. Most auto parts stores have these tools for rent, and some give all your money back when tools are returned. Excellent explanation. most leave out how other cylinders affect the problem cylinder when a valve is leaking nor look at the crank rotation in relation to compression strokes. Good job.
Excellent diagnostic Sadel! Really well explain and easy to understand the way you show it in the video! I can't believe how much we learn in every of your diagnostics cases. I was thinking about the bonus info that if we don't have exhaust phaser and no turbos and we have that exact condition at the end of the exhaust stroke during acceleration and we only have intake phaser! I've seen cat clogged but the rise starts at the beginning not at the end! I just had that in a RAV4 2006 4 cylinders at the end of exhaust stroke! Thank you for sharing, Sadel. Take care!
Thats crazy you saw your Toyota show it at the end of the exh stroke, I would almost think should be at the beginning. But maybe it's because it's at idle and not revved up, like it needs time to build up the back pressure because rpm and airflow so slow. Thank you for watching as always!
I am thinking that maybe for us (me😊) noobs it might be slightly easier to grasp by using a piston overlay chart, there is one from the drive ability guys and there is a free one in windows as well. This is a hard one to get my head wrapped around, thank you Sadel for your efforts, it is massively appreciated.
Yes I am aware of those and oddly enough on my end personally those make it more confusing for me (I know it's just me because others seem to grasp it better with the charts). I know it is a tough one, it took me forever to figure out the issue by playing in my head what the pistons were doing, and which ones were where. But maybe some repetitive watching in the areas of explanation can help. If not feel free to reach out maybe further explanation can help. Thank you for watching as always.
Thanks for sharing such good information, seeing different ways of finding a misfire or mechanical issues with engine with waveform its amazing. Once again thank you for sharing. I have a question on the pressure pulse when looking at the intake pluses, we are looking at waves going down no upwards correct? sorry if its confusing I can email you my question if you are not clear. Again thank you for sharing.
It is all going to depend on the sensors output being used. So this one is traveling down when there is vacuum or pressure is dropping, so a pull would bring it down. Hope that helps and thank you for watching
That's cool Sadel! I have asked before and understand if you don't want to, but I would get a lot out of it. If you would show your hook ups (where and which sensor you're using)for the scope when you're explaining each capture set up. Equally, super interesting and frustrating to diagnose these valve issues that a few people have covered in the last year. Where it becomes apparent that a valve has a sealing issue but only occurs in a certain orientation of the valve to seat. As the vlave rotates, the issue phases in and out. Do you think that is why you can see the wave trend in the in-cylinder peaks relative to each other? Still blows my mind that such a complex issue to catch and isolate to a diagnosis, could effectively be solved with some $10 valve lapping paste.
yes, sometimes I do just skip over the set up with the assumption some might know or other times it's to add less confusion to the diag and just explain the breakdown of the waveforms themselves. And I definitely believe the random psi issue incyl psi anomaly in the intake trace is due to the valve rotating and bleeding off in different positions
@DTEAuto you do a brilliant job! You always explain what you're tapping into for the purpose of understanding the capture channels. It's purely from a personal learning standpoint, in learning your sensor and hook up choices. The specifics would help me advance way quicker. The 2 big ones . . . I'd love to see your coolant and exhaust pulse hook ups. Coolant = I can see you use a map sensor, but I noticed you have graduated from a direct hose to a hose that has an offset Y in it. Why have you swapped to that from the early days? Are you concerned with having coolant hit the sensor? Another reason maybe? Do you find it alters the signal with it not being a sealed system to the sensor? Exhaust = are you just sticking it up the pipe a bit with a hose? I was trying to figure out how Bernie's ATS tool amplified the signal(physical pulses) to make the signal easier to read. All I can think is that it is a narrowing tube. Restricting at the exit to amplify the swing from positive pressure to negative on misfires. The sensor reference in the tube. Or maybe a bernoulli restriction and measuring on the upstream side. I just know you put a lot of thought into almost everything you do. So even the parts you might feel are rudimentary. Can be of great use to others.
it means absolutely no contribution from a single cylinder. So the engine would run but have a single dead point, almost like when you unplug a coil. Dead misfire compared to partial contribution, the engine will run and barely have a single skip that might be noticed or not, depends on how bad it isn't lighting off the whole air fuel mixture. Almost like a partially clogged injector delivering less fuel, it will ignite and burn just not have the same explosive force to turn the crankshaft as the others that got more fuel, so it will spin the crank just not well but not be a dead skip of no contribution. Hope that helps
With having the intake pulse waveform and it showing the psi bleed off anomaly is enough to know where the chamber is leaking past (i.e. intake valves) so there really wouldn't need a point to perform leak down test. The incylinder pressure test during idle was just to get a bird's eye view of the running pressures the engine is experiencing it that condition, and the great difference in pressures between the two just clearly shows us the end result of the leaking valve which is the culprit and because of the lower psi it captured it shows us why it misfires. Plus in order to perform leak down you have to gain access to the crank in order to spin it, try that on some that the crank bolt is not accessible due to being blocked by the intercooler (MB V6 Twin Turbo) or better yet like the Audi's where the fan assembly sits up against the pulley and the whole front end has to be removed and put in service mode to access the crank pulley bolt and even then they require a special tool adapter to spin the crank because there's no center bolt head. And then after that consider that you have to spin over the engine to the correct tdc position of compression for whatever cylinder and with no markings you won't know how exact you are, and lastly from what I have read or heard, doing conventional leak down has "masked" leaking valve's due to it putting pressure on the face of the valves and literally seating them tighter and not "showing a leak" Imagine doing all that work to not knowingly temporarily fix and seat the valve tighter because the air you are putting in help the valve seal. Plus, if you remember the cranking compression did not show a difference this showed its ugly face during engine operation so it's a very difficult thing to pinpoint. hope this helps explain some reasonings.
