Audi start up


My 92 Audi 100S 2.8L has a throttle lag on acceleration and rough idle.Morning start up or after sitting for 3-4 hrs.(summer or winter) the car will initially idle fine then bog or lag (do nothing)as you push down the accelerator. Push a little more and the engine will suddenly catch up. After only a minute or so of repeating this it runs and idles fine. When the lag takes place the idle is extremely rough and there is little vacuum as evidenced by lack of brake boost. Upon revving in neutral I do detect some minor popping like muted backfire.(excess fuel?) I have done plugs filters cleaned throttle body and ISV etc.

Any ideas? Thanks


Throttle position sensor. Check for volt/ohm flat spots and/or voltage spikes.


Thanks I’ll put the meter to it. I did notice this morning when I cranked the motor and had to go back in and get something it Idled for about 3 min or so I did not have the problem.