It has come to my attention that there exist 2 Bosch part numbers for the idle control valve (ISV) that are available through various sources. The part numbers differ in the last 3 digits.
I am trying to determine if a persistent "idle bounce" problem my car ('90 C4) has is related to the installation of 1 ISV versus the other. I have bought a second ISV, but, unfortunately, they are both the same number.
I'm asking that you take off your ISV and look at the number. This takes all of 5 minutes. Then post here the number and whether or not your car exhibits any idle problems (The idle bounce problem occurs when depressing the clutch, the idle will undershoot, then bounce up, sometimes stalling).
The two numbers are those ending in 531 and those in 514 (to my knowledge). This applies to 964s only, I'd suspect.