Re: 88 80: Lumpy idle when hot

[DeWitt Harrison <de@aztek-eng.com>]

On Wed, 3 Sep 1997 19:39:28 +0200 (MET DST), Tom Nas wrote:

>Here's one I can't figure out myself: my (carb'd/cat) 1988 80 1.8S idles
>beautifully when cold, almost inaudible and silky-smooth at 400-500rpm.
>When things get hotter however, idle goes to 1100-1200rpm and becomes
>rather lumpy, to the point where the whole car is shaking sometimes.
>
>It's been tuned a few times, all hoses have been checked/replaced. Being a
>non-injected car, does this have an ISV? Can't find anything in the Book...

All the carburetors I'm aware of run open loop; no idle speed control
mechanism of any kind.  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. When cold, the automatic choke may apply enough
extra draw to get adequate fuel flow. Another possibility is a bad component
in the emissions control hardware (EGR valve?) if such exists on your
Euro automobile.

DeWitt Harrison    de@aztek-eng.com
Boulder, CO
88 5kcstq