1.4 TDI engine idling roughly

Hello everyone!

I'm having the following problem:
My girlfriend's Polo is shaking quite a bit when idling and seems to be rocking back and forth. The engine doesn't sound great, and when starting, white/gray smoke is coming out from the back. It is likely unburned diesel fuel.

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

"Details:"
- First registration: 07/2006
- 1.4 TDI, 3-cylinder PD engine with particulate filter (engine code BWB).
- 120,000 km (or 120,000 kilometers)
- The timing belt has been replaced, and all other scheduled services have been performed.

due to the problem:
- Spark plugs have been replaced.
- All three PDEs were cleaned by the VW dealer.
- Compression pressure measurements indicate that cylinder 3 is not functioning correctly (this aligns with values from the VCDS-RKS diagnostic tool, which indicates an incorrect fuel injection quantity for cylinder 3). Cylinder elevation is increased (approximately +2.6).
- However, the error memory is empty.

So, I suspect that something is broken in one of the pistons. However, I'm also wondering if the problem might have a different cause. I've noticed that the fuel gauge is malfunctioning (for example, today it briefly showed a reading near 0 while the engine was running, even though the tank is at least half full - then after a while, the reading went back to normal).

Before we open the engine and inspect the pistons, I'd like to know if anyone else has experienced this problem, and whether the cause might be related to the fuel gauge issue.

Thank you very much for your help!

Hello,

If the compression pressure test results are "not okay" and the same cylinder also falls outside the acceptable range during the idle speed control test, there's no need to look any further...
Of course, disassemble.

Best regards, Rainer.

What is the compression ratio?

Hello,

Based on my general experience, I wouldn't start the engine like that again; instead, I would try to find the root cause, which unfortunately can only be determined by disassembling it.

Material costs (seals, ZK screws, etc.) for a "quick check" are approximately 150-200 EUR, plus labor costs.
I would estimate about 4-5 hours of work time for checking (including initial assessment, determining repair needs, and subsequent work). Those who do this more often will likely have a more accurate estimate.

Best regards, Rainer.

Thank you, Rainer. The house number sounds much better than what the VW workshop mentioned.

Can anyone recommend a good and affordable workshop in the Munich/Starnberg area that can take on this issue?

Best regards, Sven.




"@RedR32: The car isn't with me, so unfortunately I don't have any other data available. I took it to a VW workshop for a compression test, and they only reported 'Cylinder 3 is not okay.' I wasn't there myself." Thank you!

Hello everyone,

Was there a solution here that identified the source of the error?

Sincerely,
Markus.

Had to message the OP.
However, instead of performing a compression test, you should conduct a pressure loss test; that way, you'll also be able to identify where the air is leaking from.
There is also the possibility of a worn camshaft.