increasing idle

[Tur <getur@bellatlantic.net>]

We have a 87 5000tq that over the past two years has been gradually
increasing its idle speed. What happens is that when you start the beast
up in the morning it runs fine, the idle sits at around 800 rpm, this is
with climate control set to econ not auto, after the car warms up. After
driving the car around, say for couple a minutes or more, and then
coming to a stop the idle speed settles at around 1100 to 1400 rpms,
it's inconsisten as to what idle speed it settles at but it's always in
that range. Also after prolonged running and then coming to a stop the
idle speed bounces around, up to 1500 to 1600 rpm before it settles at
the high rpm rate. Sometimes the rpm bouncing will go through three or
four iterations before it settles down to a steady state.

At the annual tuneups I've pointed this out to the mechanic, he's an
independent that works strictly on MBs, BMWs, and Audis, and they say
that they've tuned it to the specs but the problem is still there. I've
also brought it in to the local Audi dealer for a tune up and have had
the same outcome. Both the local mechanic and the Audi dealer have
mumbled something about there maybe being something wrong with an
electrical component, such as a relay, and that it would cost quite a
bit in labor to track the problem down.

Has anyone in this usenet group run across or heard of this problem
before? I never feel comfortable in handing over the car to these yahoos
unless I have some idea as to what the root cause of the problem is. The
car runs fine aside from this fast idle.

TIA

George Tur

87 5000TQ @187000 miles and still going pretty strong