Jerking/shaking/vibrations/rough running under load from 1400-220

Hello everyone!



I'm new here, even though I've been reading the posts for years.



I used to be a certified automotive mechanic a long time ago, so I have some knowledge and understanding of engines, but as I said, it's been 15 years since I left that field.

Today I'm facing a problem that is really troubling me!



My vehicle: a VW Sharan 7N from 2011 with a 2.0 TDI CFG engine, 170 horsepower, and 220,000 km on the odometer.



My problem: I'm experiencing a noticeable vibration under load, particularly between 1400 and 2000 RPM when the engine is running at full throttle. It's most apparent in 4th and 5th gear while driving uphill with the accelerator fully pressed. I believe this issue exists across other RPM ranges as well, although it's less noticeable under partial load. Based on my experience, the vibration seems to be more pronounced when the engine is warm compared to when it's cold.



Undertaken:

Error codes read. There are no errors in the engine control unit or transmission control unit.

The reading of the injector values showed some fluctuations, which is why all four injectors were replaced.
Everyone is running well except for cylinder number 3, which occasionally deviates from the norm by as much as .5 to 3 mg. The valve cover has been removed, and the camshaft inspected without any visible signs of damage (I hope I was thorough). Swapping injector 3 with an injector from another cylinder didn't change the readings, so it's definitely not an injector issue.

I measured the compression and also couldn't detect any significant deviations in cylinder 3. However, I always only removed the glow plugs one at a time. I'm considering repeating the test without removing the glow plugs from all cylinders...

The EGR valve was once disabled using shims, but it made no difference.

Ultimately, the dual-mass flywheel was replaced due to suspected radial play. Unfortunately, this measure also did not yield any success. During this process, the clutch valves N215 and N216 on the transmission were also replaced due to hard starting and shifting. This did, however, lead to a positive result in that regard.



Does anyone have any ideas or can give me some crucial advice? Honestly, I don't know what to do anymore. We've decided to keep the car for a little longer, but this problem needs to be fixed.

It's supposed to go on a 1000 km vacation trip in 3 weeks. I would be grateful for any help, because I can't and don't want to drive like that.


Thank you all in advance!

Hello,

"That's not enough data for an analysis. If injector 3 is consistently causing problems and injecting too little fuel even though it has been replaced, and if the wiring harness is a known issue, why aren't you investigating that?"

Best regards, Rainer.

Hello,

Thank you for your feedback.

It's a common rail system, not a pump-nozzle system. Are there any issues with the wiring harness in these systems as well?
Is this a resistance to ground? Is there any information about the location of this issue within the wiring harness?

Hello,

I am not aware of any widespread cable issues with CR. Of course, that doesn't mean problems never occur.

Why don't we compare?
I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

Sure, here is the translation of the text from German to English:

"LG" translates to "Best regards" or "Sincerely" in English. It is a common abbreviation used at the end of emails and letters.

I'm ruling out the injectors because cylinder #3 has already had three different injectors installed (two of which were new with a test report), and the fuel injection quantity calibration value always remained the same.
The problem didn't transfer when swapping between two cylinders.
I'll still check the injection calibration pressure, just for good measure. But as mentioned above, this is a reliable method to rule out the injector in cylinder 3 as the cause of the problem.

"Please perform a pressure loss test."

Today, I checked the compression again. This time with all spark plugs removed and a fully charged battery!

Cylinder 1: 25.5 bar.
Cylinder 2: 25.0 bar.
Cylinder 3: 19.5 bar.
Cylinder 4: 19.0 bar.

So, it doesn't look very good at all. Now the question is where the leak is coming from. Since two adjacent cylinders have approximately the same low pressure, I wonder if there might be a crack in the engine block between cylinder 3 and 4, or if it could be a head gasket failure between those two cylinders.

The leak tester has been ordered. To use it, the crankshaft needs to be fixed at the top dead center (TDC) position of each cylinder. How should this be done?

Do you have any guesses yet? Could the camshaft be damaged, causing a misfire on two cylinders (would this already be noticeable during a compression test)?

Meanwhile, the solution to the problem has been found, and I think it's important to share it here. In short, it was the head gasket!



I'm not sure what I messed up during the compression test.

The repeated measurement showed 25/25/19/19 bar. Subsequently, I performed a pressure loss test and discovered that cylinder 3 has air leaking into cylinder blower, and vice versa.

During the disassembly of the cylinder head (a really unpleasant job on a Sharan, especially without a lift), I also noticed cracks between the valves, so I replaced it immediately because I didn't know how deep they were. However, it's possible that the engine actually needed a little water.



Please look at the pictures yourself.



The vacation went well, and we've now driven 3000 km. It also drives like new, partly thanks to the new injectors.