'88 80q idle weirdness...

[Huw Powell]

> I have had my '88 80q for about 8 mos now and aside from a big hole in the
> heater core and a dead WOT/Idle switch it has run darn near flawlesly.  It
> is actually amazing to me how well it runs at 15 years/135k miles.

It's still just a baby at 135k...

> thing that might be considered a problem is that it idles at ~1000 rpm.  Ok,
> not much to worry about especially since the idle is rock steady.
>
> Recently on hot days (90+) when I get it fully up to temp and then shut it
> off for 30-45 minutes and then start it again the idle will surge.  1000rpm,
> 12000rpm, 1000rpm, 1200rpm at about 3/4 second per cycle.  If it sits less
> than 30 minutes no problem or over an hour again no problem.  I assumed it
> was the ISV so this evening as it was ideling I disconnected it expecting it
> to settle down.  It didn't.
>
> Any ideas?  There are no codes, and once things cool down some it will be
> fine again.  the ISV is very warm to the touch but so is everything else
> under the hood.

Yes, fix that busted idle/WOT switch.  Until the idle switch works, the
ECU doesn't even know to try and regulate the idle, meaning that the ISV
isn't doing anything anyway.  New ones run around $70, as I recall.
Used ones I wouldn't trust - since it is a bit awkward to install, why
do it again next year?

> Oh one other thing, the 1000RPM dle will drop to 800RPM if I turn on
> something that draws a lot of current like the rear window defroster or if
> the cooling fan comes on.

Because there is a load, and as I said, the ECU isn't "doing anything"
about it.

--
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/