My car shakes when accelerating only

[Bee7even]

I have a 2008 Audi A4 automatic 2.0 TDI with 248xxxkm on it. It vibrates and shakes the entire car when accelerating and also when it's standing still except for when it's in neutral. I have also checked that when i change from Park to Reverse or from Reverse to Drive etc. the engine shakes.
What can be the cause of this?
I have balanced wheels, changed my left drive shaft (going to change the right one tomorrow because it's defective too) which helped a bit. Engine mounts are changed too which helped A LOT for a while, but the shaking came back after a few months. There are some defective bushings on the front axle and a turbo tube is loose (maybe it sucks in unfiltered air?).
It doesn't matter what speed I'm going at, if I let go of the gas pedal, the shaking stops. And it shakes especially hard when I'm going uphill on the highway.
I have watched a lot of videos and read a lot of forums and some even suggest it may be the dual-mass flywheel.
I would appreciate any help at all as I have limited funds and don't want to waste any more money on this car.

 

[obi_waynne]

You mentioned that replacing the engine mounts initially helped a lot, which is a great clue. Engine mounts are crucial for absorbing the vibrations and movements of the engine. If the shaking returned after a few months, it’s possible that the mounts might be faulty or of low quality. It might be worth revisiting this area. Cheap mounts often fail quickly and could lead to the return of the shaking.

Dual-Mass Flywheel​

Your research about the dual-mass flywheel could be on point. These components are designed to absorb vibrations to make the engine run smoother. When a dual-mass flywheel fails, it can cause intense shaking and vibrations, noticeable both when accelerating and at idle. Given the symptoms and the mileage on your car, this is a strong possibility. The flywheel's deterioration would fit with the shaking stopping when you release the gas pedal and the increased vibration under load, such as going uphill.

Does the DMF rattle when idling and accelerating? Listen for a rattling noise from the flywheel area when the engine is idling. The noise might decrease or change when you press the clutch pedal if the DMF is at fault.

Loose or Damaged Turbocharger Components​

The loose turbo tube you mentioned could also be contributing to the problem, especially if it’s allowing unfiltered air into the engine. This can upset the air-fuel mixture, potentially causing rough running or misfiring under certain conditions. Fixing this should be a priority, as it could also lead to other engine issues down the line.

Drive Shaft and Bushings​

You’re on track with planning to replace the right drive shaft, given the improvement after replacing the left one. Also, consider the defective bushings you mentioned. Worn bushings on the front axle can significantly affect the alignment and stability of the vehicle, leading to vibrations, especially at higher speeds or when under engine load.

1. Reassess the Engine and Transmission Mounts: Make sure they are of high quality and installed correctly.
2. Inspect the Dual-Mass Flywheel: Have a mechanic specifically check the condition of the flywheel. This could be the root cause of your problems.
3. Secure the Turbo Tube: Fix this to ensure all connections in the turbo system are tight and secure. This might solve the issue or at least improve the situation.
4. Complete the Drive Shaft Replacement and Address Bushings: Since you saw improvements with the drive shaft change, finishing this job might further reduce the vibrations.
5. Diagnostic Scan: If the problem still persists, a full diagnostic scan might reveal underlying issues not immediately apparent.

Given your situation with limited funds, it's wise to approach this methodically. Prioritize repairs that address multiple symptoms or seem most likely to resolve the major issues, like the flywheel and turbo tube. Remember, solving one big problem might eliminate what appear to be several smaller ones.