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Re: 88 80: Lumpy idle when hot

Hi DeWitt,

>All the carburetors I'm aware of run open loop; no idle speed control
>mechanism of any kind.

That's what I thought. No diagnostics blurb in The Book.

  Two thoughts on the idle problem: a piece of
>dirt may be lurking around the idle circuit (speed adj. needle valve, idle
>air screw or idle jet.

I've tried carb cleaner. It melted the lens of the flashlight I used to see
where I was spraying (strong stuff!) but did nothing whatsoever for the
idle, whereas I've used it with success on other cars previously.

 When cold, the automatic choke may apply enough
>extra draw to get adequate fuel flow.

It's got a manual choke. I've tried pulling that when idle was lumpy, but
it just made it run bad at higher revs.

 Another possibility is a bad component
>in the emissions control hardware (EGR valve?) if such exists on your
>Euro automobile.

Hmmm... now where would that be located?

Another idea pops up: Could it just be a worn-out carb? ($$$)

The problem is intermittent, BTW. Last week it was horrible, this week it's
so-so. Today, idle was near-perfect. Still, it runs best when the engine is

Thanks for your ideas so far, please keep 'em coming!



 Tom Nas                                          Zeist, The Netherlands
1988 Audi 80 1.8S, Tizianrot metallic, 212,000km

  Half a bee, philosophically, must ipso facto half not be. But can it be
  an entire bee, if half the bee is not a bee, due to some ancient injury?

                                                -- Monty Python