Which Knock Sensor????
 

I am in the middle of doing an intake refresh on my 1990 S4 (cat) in the hope that this will help sort out the idle problem I have. I have found some things that need replacing right away such as the two knock sensors.

There seems to be two knock sensors you can buy. One had a black connector (with tin contacts and one a blue connector with gold plated contacts. Will either of these work on my car. Any help would be great as there seems to be a price difference between the two!

The blue/gold plated ones are for the GTS but you can use either one, it won't make any difference.

Change everything while you are in there as you don't want to do the job 2 or 3 times.

928 and 944 use the same sensor with a slightly different length cable, same connector or compatible anyway. 928 is a lot more $$$.

Whenever you are in doubt on any 928 part, use one of the knowledgeable 928 vendors, not cheapest via Google etc or it will bite you in the behind frequently.

I realize I am not really answering your question but I spoke to a guy today who had been trying to figure out his idle problem in his '91 S4. After attempting everything he got a new ECU and the problem was fixed.

Rough idle can be from so many different things, its not one of the "good" problems to have with a 928.