I picked up a 1990 Audi 80 Quattro rally car. I'm sort of brand new to all things Audi, but I figured why not take the plunge and jump in head first, which is kind of crazy, which sounds about right for me. Anyway, the car is a bit of a Frankenstein- it has a KH motor in it from an 85 turbo. Ur CIS. Clutch is from an Audi 200 20v. And the the transmission and difs are 4000 quattro.


Car runs fine, idles fine, revs throughout the range smoothly. In gear, the car will run OK for about 1-2 mins. Then, when under load in gear, it first hesitates, stutters while accelerating. Then the problem gets worse fairly quickly to the point where when accelerating while in gear it bucks wildly, engine cuts, and I have to clutch in to stop it. You can almost minimize the problem if you barely give it throttle, but not by much it seems. Then power loss gets so bad, it won't even make it up the driveway.


I've scoured everything I could think of for vacuum leaks. I haven't done a PSI test on the injectors, but did a volume test, which was fine. So, onto sensors, unless someone can suggest some really elusive leaks to check for.

I have the MAC 11B ECU which has been modded by Intended Acceleration.

Here's what I know and have tested for on that front:

Pins 23 to 24 (intake sensor to ground) are supposed to be 13-33 ohms at room temperature. Mine measures 470 ohms. It was 45 degrees outside. Normal?

Pin 20 (idle switch) to ground measures 35 M ohms!, then climbs to an OL state. This is confusing.. Closed it's supposed to be 0, opened it's supposed to be infinite. I guess you could say it's shot?

Is there any way to check the Hall sensor? Any way to check the knock sensor?

Are there any other sensors I should be checking?