Mercedes ml500 cam / crank waveform 2003

Hi all ! First time on the forum so hope I'm doing this right ! I'm a diy guy and I'm working on a 2003 Mercedes ml500 it seems at idle that it has a misfire which goes away as soon as you raise the rpm no dtcs or miss fire monitors .you can here it miss through the intake by way of a light popping ,so I thought of a bad inlet valve ? Just done a leak down and all are between 10 to 14% which didn't seem to bad with all leaking evenly between oil and intake as best I can hear . It did have positive fuel trim total of 6% bank 1 and 8 bank 2 but new plugs brought down to 0 with short term switching from -1to +2 so no problem there .i don't have a presure transducer for my peco but have done a relative compression ( starter current and signal from spark plug 1 and it appeared that the bank 1cylinders (1234)had there peaks on average 6 to 8 degrees after where there coil would fire (added in the 8 X 90 deg divisions ) thinking of a slightly stretched timing chain ? Can I really use the current as accurately as that ? I've just done a cam crank waveform with coil 1 which looks ok but need a known good ?.? If anyone could help with a waveform I'd really appreciate it oh and it only has 1 cam sensor and it's on bank 1. Thanks Chris

Hi Chris, welcome to the forum!
I see some people have viewed you post, but no one seems to have that waveform yet. Bummer, I don't have it either.
Nothing from Google, Alldata usually doesn't provide this info (and this case is no exception). I'm not a sponsoring member of IATN, so I don't have access to the waveform library.
Someone around here should be able to help with that.

Can you take a screen capture of the waveforms and post them up here as a PNG or something?

hi thanks for your reply ,i did reply to you with 3 waveforms but i cant see them up so will add each indervidualy the 1st is the ml500 ith cam and crank and ingnition no1 ,the 2nd is the cranking and ignition no1 and 3rd will be a different car showing how i exspected the ignition to line with the cranking peaks /tdc

I'm not seeing them, sorry.
Make sure to check out the posting guide for pictures Here .

I suspect the files are just too large.

yes you are correct there 5.6 mb per pic ill try and reduce them thanks chris

ok try these

hi ive resized them add files then attach it puts the file title in the box but not a viewable pic? and when i go to send it says the box is empty what am i doing wrong?

Click "Add File"
Choose the pic you want to upload
Click "Insert"
Then when you're all done, submit.

Late to the party, sorry guys! I found something on iATN:



There's not much info to go with this capture, but I'd guess that the red and blue traces are both wires on the CKP, and the green trace is the CMP. Yellow is an ignition sync, probably cylinder #1?

Hope this helps.

hi thank you very much for the post ,it is as you described athough i only picked up one wire from the ckp, green is indeed the cam and i think your correct with the yellow being no1 athough mine is dead in line with the trailing edge of the cam but thats at cranking and this may well be running . so from this i would say my timing is fine .i have tried to upload my waveforms but it will not have it so i need to find out whats going wrong .very kind of you both to take the time to help regards chris

IT WORKS !!!!!! THIS IS THE RELATIVE COMPRESHION WAVEFORM WITH NO1 IGN FIRING ORDER IS 15486372

THIS IS A RENAULT CLIO 09 1.2 SAME TEST BUT A 4 CYLINDER . NOT SURE IF IT WILL BE CLEAR ENOUGH SINCE I RESIZED PIC BUT ON THE ML500 WAVEFORM THE SPARK EVENT ON 1234 ARE ALL BEFORE THE PEAK ABOUT 6 TO 8 DEG YET 5678 ARE NEAR AS BANG ON ,THE PICK MAY NOT SHOW THE 8 X90DEG LINES

AFTER HAVING A BETTER LOOK MY TIMING IS OFF !IF YOU MOVED YOUR GREEN CAM ALONG TO TOUCH THE YELLOW TRACE THIS IS HOW MY WAVEFORM LOOKS ,MY GREEN CRANK IS YOUR BLUE AND THE TRAILING EDGE OF THE SINK IS NEARLY IN THE MIDDLE OF YOUR CAM BUT ON MINE ITS ABOUT A 1/3 . THATS GREAT NEWS THANKYOU

ChrisG wrote: AFTER HAVING A BETTER LOOK MY TIMING IS OFF !IF YOU MOVED YOUR GREEN CAM ALONG TO TOUCH THE YELLOW TRACE THIS IS HOW MY WAVEFORM LOOKS ,MY GREEN CRANK IS YOUR BLUE AND THE TRAILING EDGE OF THE SINK IS NEARLY IN THE MIDDLE OF YOUR CAM BUT ON MINE ITS ABOUT A 1/3 . THATS GREAT NEWS THANKYOU

Is that great news? :huh: :lol: Most aren't so happy to find a timing problem, but I'm happy that you're happy!

Thinking about a jumped chain?

Tyler wrote: Late to the party, sorry guys! I found something on iATN:

There's not much info to go with this capture, but I'd guess that the red and blue traces are both wires on the CKP, and the green trace is the CMP. Yellow is an ignition sync, probably cylinder #1?

Hope this helps.

Do you think the fluctuations in the A/C signal indicate that this was a cranking capture?

Noah wrote: Do you think the fluctuations in the A/C signal indicate that this was a cranking capture?

Maybe? ChrisG's waveform shows the same oscillations... Good eye, sir!

Now I'm looking closer at the CKP signal... this is a V8, right? So, there should be eight points in 720 degrees where the engine 'slows down' to run a cylinder through it's compression stroke.



I only count six? I'm not saying Chris is missing compression on two cylinders, I'm saying I can't be looking at this right. :lol:

Great news that it's what I suspected from the other waveform ,oh and it's not my car it's my brothers ! Know if it was on my car I would be deep in trouble that would be engine out

Tyler wrote:

Noah wrote: Do you think the fluctuations in the A/C signal indicate that this was a cranking capture?

Maybe? ChrisG's waveform shows the same oscillations... Good eye, sir!

Now I'm looking closer at the CKP signal... this is a V8, right? So, there should be eight points in 720 degrees where the engine 'slows down' to run a cylinder through it's compression stroke.

I only count six? I'm not saying Chris is missing compression on two cylinders, I'm saying I can't be looking at this right. :lol:

Yeah, good eye. That's hard to justify...
Even the known good has only 6 of those "events" per 720 degrees of rotation

ChrisG wrote: Great news that it's what I suspected from the other waveform ,oh and it's not my car it's my brothers ! Know if it was on my car I would be deep in trouble that would be engine out

Ooooooh OK, gotcha! Well, let him worry about it then, right? :lol:

What does Danner say ...I diagnose it and tell Pete to fix it