Engine running rough or misfiring can be cause by the following:

1.Defective spark plug.
2.Inadequate spark/coil,defective spark plug wire.
3.Lack of compression
4.Vacuum leak
5.Fautly fuel injectors.
6.Insufficient fuel pressure.
7.Contaminated fuel.
8.EGR valve that is leaking.
9.Oxygen sensors.

Answered by rasmataz
68 questions asked

First thing to do is scan the ECM. There will be codes if it is mis-firing. Some common faults on your engine are MAF's, EGR's, turbo pressure pipe leaks, ECT. A lot of things can cause your TDI to misfire. Scan the ECM and post the codes.

Answered by F4I_guy (expert)
3,238 answers provided