intermittent idle issues, not ISV

[Huw Powell]

David.Ullrich at ferguson.com wrote:
>
> OK, I've got a 1987.5 Coupe GT (NG engine). I've got an intermittent idle problem. It always starts fine (cold or warm) but after idling for a minute or so it may start bouncing from 900 - 1600 (can't be exact as I have a digital dash). It never falls below 900 or so. It slowly raises up to 1600 then dumps back down. I know the ISV is working properly and is clean. When removed, it opens and closes smoothly and quickly when applying 12 volts.  Oh, the idle issue doesn't always happen and if it is happening I can just turn the car off then restart to cure it for a while. Any thoughts? Excuse the amateur question...I'm new to this car...

Well, your ISV may be testing as "ok", but is it actually *working* on
the car?  Does it sorta hum or buzz at idle?  There's a test connection
hanging around near the battery that let's you measure the ISV duty
cycle, which is what the ECU is trying to get it to do.

and, at the risk of being *truly* redundant, see the mock addition to my
sig file....

--
Huw Powell

"Undo every electrical connection under the hood one at a time, clean
them, and reassemble with dielectric grease to seal."

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

http://www.humanthoughts.org/