88 80Q won't start or idle when cold unless you crack the throttle

Huw Powell audi at humanspeakers.com
Sun Oct 15 16:04:47 EDT 2006


> The car will not start when cold unless you press  down on the gas just the 
> smallest amount. If you crack the throttle, it will  start right up, if you 
> take your foot off it tries to idle at about 400  RPM.  When cold you can make 
> it idle ok ~900 RPM by applying a little gas  by foot, the mixture is correct 
> because no mater how cold it is it idles  smoothly (with your foot on the 
> gas). After a few minutes (or miles) you can  remove your foot and it will idle as 
> normal. When hot, just  hit the key  and it starts up right away.  The heater 
> core replacement requires a  complete dash removal and lots  of wires were 
> disconnected. I didn't have  to touch any wiring under the  hood.
> The car started perfectly when cold  before the heater core operation and 
> still runs great, it's just that something  isn't right.   Any ideas?

Cracking the pedal a tiny bit does two things - one is of course to open 
the throttle slightly, so perhaps there is no air with the throttle 
closed.  That might point to an ISV problem, as some suggested. 
Cleaning it and working it out a bit with a 9v battery could help.

The other thing that happens is the idle switch is opened.  When it is 
closed (foot off pedal), the ECU trims the engine to a fuel efficient 
mode, and controls the rpms via the ISV.

I don't think there are any underdash connections between the ISV and 
the ECU, except the main ECU plug, and, I suppose, the ECU's power wiring.

It sounds like the ECU is running right, since you are getting cold 
enrichment (it would run like crap cold without it) so it must be 
plugged inproperly and getting power.

It really does sound like your ISV is stuck closed when cold.

-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/


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