[1988 90Q MT] Fault Codes

[Huw Powell]

> 4431 (Idle Stabilizer) - "problem in wiring" according to Bentley, although
> you can hear it clacking away when doing the output checks.  The car idles
> too high(~1200 revs) and occasionally dithers between 1000 and 1400 rapidly
> when warm.  I've checked the valve, and when it's at rest you can blow air
> through it - the "window" is partially open at rest. I'm thinking that the
> soft brass adjustable "stop" it has been hitting for the past 13 years has
> allowed the little rotary valve to close too far, which actually results in
> it being open.

partially open is its rest state, it can be run at various duty cycles
by the ecu resulting in the required amount of air to maintain the
idle.  Yours is probably sticking rather than being "closed" more often
when warm.  When it unsticks for a moment, your idle drops properly,
then it sticks, idle comes up, repeat as necessary.

try removing it and cleaning with carb cleaner, also make sure the
electrical connection is clean.

-- 
Huw Powell

http://www.humanspeakers.com/audi/

http://www.humanthoughts.org/