I have an A4 1.8T from 2001 with about 70K miles on it. Its has for a few months now run very rought at idle, whether going from Park to Drive, coming to a stop at a light, or beginning to accelerate from a stop. The tachometer dips and rises between like 800-1200 and the car wants to lurch foward, then hesitate, then lurch foward again (in concurrnce with the tachometer ups and downs). Once you start to accelerate or cruise normally the problem is gone, only at idle, stop, start periods.

I have heard many theories about this problem. From bad igintor coil, to messed up throttle, to dirty parts. Frankly, the engine just might need to be tuned, the timing could be off. Im just not real sure what the problem is. I tried Fuel Injector cleaner and that didn't help. Any other ideas or suggestions. Thanks!

 

Try cleaning the trhottle body intake.

Any codes? having those read may help.

GL!

 

I feel your pain man, mine is doing the same thing.
You should find an OBD2 tester to borrow and see what the computer has to say about the situation.

 

COOLANT SENSOR!!! Trust me!!!

 

Ill get the codes up in a little bit. Thanks for all your help guys.