Can the idle stabilizer valve be bad and still pass the Bentley tests?
I had the same problem with my '86 GTI (CIS-E). Sometimes it idles fine, but many times when I let off the gas it drops almost to 0 RPMs.
I haven't replace the O2 sensor, so it could be bad and I haven't checked the timing, but I've done most everything else:
- new plugs, wires
- new vacuum hoses
- checked intake boot
- cleaned idle stabilizer valve
- cleaned throttle body
- checked idle switches
- new coolant temp sensor
-Mike