Mercedes ML350 valve timing question using pressure transducer

Alex Technician Colorado Posted   Latest  
Updated
Driveability
2009 Mercedes-Benz ML350 4Matic 3.5L (272.967) 7-spd (722.9) — 4JGBB86E29A485555
P0016 — Crankshaft Position - Camshaft Position Correlation Bank 1 Sensor A
P0300 — Random/Multiple Cylinder Misfire Detected
Misfire

Hello everyone. I'm posting this question because I'm trying to get better at using the pressure transducer to determine valve timing problems. I have this ML350 in the shop with the above DTCs. I connected the scan tool and viewed misfire data and found dead misfires on cylinders 1 and 4. I ran some tests and found the ignition coil for cylinder 1 is bad, and I have an intake valve leak on cylinder 4. However I still have this P0016 to address. I installed a pressure transducer on cylinder 1 and took this waveform. My question is can this waveform be used to determine advanced or retarded valve timing? Based on the information I've found, using the degrees cursors in the pico software this looks like the cam timing is advanced based on the exhaust ramp and retarded based on the intake ramp. I say this because the exhaust ramp and intake ramps are both well outside of the 2nd of the 4 partitions aka the exhaust stroke. Can anyone shed light on this?

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Craig Technical Support Specialist
Illinois
Craig
 

Alex could you please repost the file as this one isn't opening.

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Dmitriy Analyst
Ontario
Dmitriy
 

It opens fine with Picoscope 6.14 diag​.​net/file/f5snttzwk… ​

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Craig Technical Support Specialist
Illinois
Craig
 

Thank you Dimitri.

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Scott Owner/Technician
California
Scott
 

Hi Alex, I downloaded your file and measured out the valve timing events. I'm not familiar with this engine so I don't know what's good or bad but what I arrived at is the EO = 57 BBDC and IC = 68 ABDC. Is this a V engine? If so, sample a cylinder on the other bank and compare. I also added the saved PICO file with the cursors set up for measuring the EO angle.

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Craig Technical Support Specialist
Illinois
Craig
 

Alex, you are absolutely correct in your diagnosis. I have attached 2 files from ATS, thank you Bernie! I keep these saved to my desktop as a quick reference. If you search the site for in cylinder waveforms you will find several great tutorials here in diag​.​net

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Alex Technician
Colorado
Alex Update
   

I appreciate all of the responses. Comparing this waveform from cylinder 1 to a capture from cylinder 4 on bank 2 (this is a 3.5 V6), this exhaust event on cylinder 1 does look much longer than what I suspect is normal. I'll attach a pico file showing cylinder 4 which I found to have a leaking intake valve. However, cylinder 4 is on bank 2, which uses a separate timing chain from bank 1, and I…

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Dale Diagnostician
South Dakota
Dale
 

Alex what software can we use on Android devices to view these files as I download them but I'm not offered any option for viewing as in software suggestions generally when there's not a associated app with a certain file type on Android. I wonder if this will be the same situation on Apple devices with the iPads? MY guess with the way tech is moving, the Advanced phones, etc it's probably…

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Alex Technician
Colorado
Alex
 

I see people post pico images on here without uploading the pico software file, I'll have to figure out how to do that.

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Bob Owner/Technician
Massachusetts
Bob
 

Alex, If you want a good capture from the opposite bank for comparison you should use a cylinder that doesn't have a misfire. You said 4 had a leaky valve and the will affect the shape of the waveform. I would take a capture from a good running cylinder for comparison. That being said, a transducer test on 4 should help you confirm a leaky valve.

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Alex Technician
Colorado
Alex
 

Good point. The customer already declined further repairs. I'll see if I can get the vehicle back in and take another capture.

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Dmitriy Analyst
Ontario
Dmitriy
 

“I noticed that the exhaust event is only about half the duration on cylinder 4 (about 44 ms) as on cylinder 1 (about 92 ms). ” Alex, the engine RPMs were quite different when these two waveforms were collected. It is very hard to compare milliseconds because of that. Here is the screenshot of the waveforms merged by the phase rulers. File1 is your Cyl 1 capture, and dashed traces come from…

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Alex Technician
Colorado
Alex
   

Yes great point. The firing order on your chart is correct. Are you calculating RPM with a built-in function of the pico software? I don't know how to do that.

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Dmitriy Analyst
Ontario
Dmitriy
 

With the 0-720 phase rulers placed on compression towers, set the time cursors on 0 and 360 marks. Then the RPM will be displayed in the bottom-right corner. More on that here: diag​.​net/msg/m3t0a79qvr…

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Alex Technician
Colorado
Alex
 

Awesome thanks Dmitriy.

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Justin Mechanic
Tennessee
Justin
 

[REMOVED]

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Alex Technician
Colorado
Alex
 

The service info I have shows this engine has a primary chain and then 2 secondary chains, 1 for each bank. Intake and exhaust cams both directly chain driven.

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Justin Mechanic
Tennessee
Justin
   

[REMOVED]

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Alex Technician
Colorado
Alex Update
 

Here's a running compression test captured from cylinder 5 on bank 2 of this engine. I noticed the exhaust ramp does not appear advanced using the rulers on this one when compared to cylinder 1.

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Bob Owner/Technician
Massachusetts
Bob
 

Yep, that's a lot different than cyl 1. Timing is definitely off on cyl1.

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