i have a 04 audi a4 1.8t fwd auto and it has a few problems that im trying to fo fix..

first of all wen the engine is on and the car is idling it shakes and rpm goes up and down randomly, i changed all spark plugs and ignition coils and didnt solve the missfires. plus the car wastes twice as much gas as usual because of the missifre i suppose..

i got it checked in different places and they all tell me different stuff so i dont know wich one to believe since i dont want to start changing parts that dont need to be changed..

some told me it might be an air leak, some said fuel pump, some said mass air flow sensor, and the last one i went to that seamed like he knew what he was talking about said its the throttle body positon sensor.

Another problem i have is that when im driving, the car all of a sudden goes in limp mode and then the car goes in neutral by itself and i have to stop the car, hit the break, and then accelearate again in order to work so i dont know if these problems are related or not

I need some advice in what part is causing these problems if anybody can help

 

For gods sake, WHAT ARE THE FAULT CODES? These cars have on board computers for a reason. If changing your plugs and coils didn't cure your misfires (if thats what it really is) you have a vacuum leak. Of course i could easilly tell you whats wrong with it with fault codes in hand.

Your second issue needs a vag com scan tool to diagnose.

 

Take your car to autozone or pepboys or advance or whoever. Have them scan it. Tell them to print your code faults. Post them up. Dont trust the people at those stores to know what is wrong with our cars.

 

AUDITECH79...I'll give you some fault codes! I have the same problem...04 A4 3.0 Quattro. My problem consists only at cold start up. My car runs great, however when starting up cold, I can hear the car misfire and check engine light comes on with codes as follows. The misfire happens for about 5-10 seconds and goes away and the car runs great again. The machanic has had it for going on 2 weeks and can't figure out the issue yet. I need an expert bad!

3 Faults Found:
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 008 - Implausible Signal - MIL ON
16689 - Cylinder 5: Misfire Detected
P0305 - 008 - Implausible Signal - MIL ON
16690 - Cylinder 6: Misfire Detected
P0306 - 008 - Implausible Signal - MIL ON

What do you think?