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Hi there ! New to this forum because I just purchased a 1988 Audi 90 w/2.0 4 Cylinder engine.
Car ran fine on the way home except it bucked a little bit (like when you let out the clutch too fast).
Now, I have sold my other car, and this one quit on me !!
It runs fine when cold, but after it has been driven a short distance, it starts to buck violently and won't move (runs fine in neutral).
I have replaced the fuel pump and distributor, but it was no help and it is getting expensive.
Please help !!
Thanks !!
 

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shoes VW you have obviously checked the two things taht i would have checked first the fuel pump and distributor-
have you checked ;
the fuel tank vent- run it without the fuel cap on to see if it helps
the fuel filter
vacuum leak at the throttle body or inlet manifold-visual check or you may hear some hissing/suction noise
dodgy spark plugs (check the gaps)
ht leads
ignition coil???
cylinder compression
its a bit wierd that it runs fine when cold and starts to run erratically when warm this may indicate that the temp sensor connected to the injection system may be faulty giving an over rich mixture

hope this is of some help
dave
 

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get your timing and cam belt checked. My coupe bucked despite new fuel filter and the cam went, i've now sold it for scrap. heartbroken
 

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Another thing to check would be the throttle position potentiometer. I had a VW passat that displayed the same symptoms that you describe.

The throttle position potentiometer (maybe a switch) is used to tell the computer when the throttle is closed. If the engine is spinning faster than about 2000rpm and the throttle is closed then the fuel is cut completely (overrun cuttoff to save fuel). If the potentiometer (or switch) is faulty the computer gets a signal that the throttle is closed when it isn't and cuts the fuel, causing the violent bucking. When the engine speed drops below 2000rpm everything the idle control takes over and fuel is metered again.

Good luck.

Keith853
 
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