Please help! I have a 1991 Audi 100 that is flawless and paid for. 215,000 miles and doesn’t leak or use a drop of any vital fluid. It does have one problem: While under load and accelerating from a dead stop, about 75% of the time the engine hesitates as if it is not getting any fuel. You step on the accelerator, get no reponse for one second and then off you go, no problem. On occasion while accelerating from a dead stop, the engine will quickly cough, pop like a backfire, and then catch. I have replaced the fuel filter, and through accident inadvertenlty found out that I seem to have excellent fuel pressure. While at speed, I seem to have little or no problem with instant acceleration when the accelerator is pressed. Local Audi mechanics have been unable to tender any solutions. Any viable solutions are appreciated. It would be a shame to let this car go.
I think this model still used a form of CIS fuel injection and it does have some quirks.
The first thing is to make 100% sure there are no intake manifold vacuum leaks or intake tract leaks.
CIS does not tolerate air leaks at all as any leak affects the fuel pressure sensor plate in the fuel distributor.
Retarded ignition timing for whatever reason could also cause this as could a problem in the fuel distributor.
How did you find out that the fuel pressure is excellent? Should I assume that you got sprayed during the changing of the filter? If so, that test doesn’t mean anything… 