Mercedes w204 running fault - help interpreting cam/crank and in-cylinder pressure
Vehicle: Mercedes W204 MY2013, Engine: 274.910 - VIN:WDD2040312A839282 (always unable to enter in the field above for some reason).
Car has a fairly consistent running fault. It feels like a typical HT-type issue, but have taken the opportunity to gather some scope data targeting potential mechanical valve timing issue - the stored faults report issue with the crank signal (see log attached). For the record, we have looked at the plugs - they could do with renewal, but don't reckon they are responsible for the fault.
If someone can kindly take a look at the attached cams vs crank scope data and advise. Also if someone could point me towards, or contact against a known good for this, that would be great.
I've also got in-cylinder pressure traces for all 4 cylinders (cranking with cam adjusters disconnected). I'm very new to this, but from what I've learned to this point, the pressure traces don't look correct (see attached). Note that I didn't cap off the intake, which I do know can affect valve event definition. All cylinders are pretty much the same. We used 4x transducers to make this file. Again, if someone with superior wisdom in this area can comment that would be fantastic.
Thank you and I look forward to the chat!
Hi,these engines are known for stretch timing chain,rule this out and swap the coils if you have from another car.
Is the 4 cyl engine a 1.8 or a 2.0T. The consistent running fault means a rough idle or misfires? Do the P0339 ckp codes set at start up or at high rpm? In the scan data, does the Desired and Actual cam timing match at idle and while cruising? Does the engine have 1 or 2 knock sensors. Does the P2339 knock sensor code set on start up? Is the engine noisy? Is the PCM retarding the ignition…
Adam, did you capture the crank signal at the sensor or at the module? Is the code set a short time after the startup or not?
Hi Dmitriy, the codes reset after startup. The cam/crank capture was taken via breakout kit (sub optimal, I know).
See atached modified sensor
Interesting. Thank you for this, Kevin!
My concern is I see no intake pull in your capture
The capture was taken with the engine cranking, so you will see very little cylinder vacuum pull during the intake strokes.
Capped off intake and repeated in-cylider pressure test (cranking - see attached, per cylinder). The exhaust events looks a little advanced to me. Perhaps indicative of chain-stretch? Thinking next move would be to strip and confirm timing via manufacturer's marks etc. Would love to know your thoughts on the pressure traces guys...and thanks for all input so far!
Just wait a second... If you think the exhaust events are advanced, this means the exhaust valve should close too early (before 360 mark) as well. How would then the waveform look in the 300-360 region?
Pressure should spike as the exhaust stroke finishes with the exhaust valve closed early and before the intake valve opens, I think. What could cause that hitch that every cylinder seems to have just after TDC compression? I don't recall seeing that in any "good" in-cylinder traces, but I've admittedly not seen as many as I'd like.
Go in to your pico and pull a in cylinder wave form .under demo mode and compare
Exactly, Jj! There would be a hump on the waveform, but there is none in that region on Adam‘s capture. Proof by contradiction, so to say. Now about that “hitch”... very unusual... might be some quirk of pressure transducers used, but could be real... Almost looks like something mechanically shifts after crossing TDC... but I have no idea really!
I am not nearly proficient enough with in-cylinder to say for sure if the "hitch" is a rabbit hole or a valid diagnostic direction, but I'll throw in my thoughts on the hitch itself Gut feeling on that hitch in the waveform, assuming it is not just a weird artifact, is that there is a very slight/short duration leak occurring during the power stroke. It's a more rapid drop off of pressure for a…
Thanks all! To advise, I can confirm that the “hitch” is real. I’ve taken a number of other cylinder readings and this feature is not consistent. I will be revisiting this one later in the month and will update on further testing in dues course.