Strange M5 idle problem

[Jim Walsh <jimw@xxxxxxxxxxxxx>]

I'm having a strange problem with my '91 E34 M5.

When I start the car cold in the morning (in an attached garage so never
below 52 degrees or so), it runs just great.  Runs fine on the highway, just
dandy on the track, whatever - no problems at all.

If I shut the car off and leave it for 15 or 20 minutes, plus or minus - go
to the grocery store, whatever, the car has a low idle after I restart it,
and it lasts for a while - 10 or 15 minutes.  Low to the point where it's
stalled at times if I let the revs drop quickly (like pushing in the clutch
and releasing accelerator when coming to a stop).  I have to drop the revs
very gently to ensure it'll work fine.

It's in the shop (Strictly BMW in Bellevue WA), they say HC's are all over
the place, their current theory is dirty injectors.  They've replaced the
plugs, say the spark pattern is better, but problem still there.  My problem
with these theories is they don't address why this would only happen after
restarting it when warm.  O2 sensor output is fine they say.  The injectors
were likely replaced 30,000 miles ago (when the previous owner had it
stroked by Dinan), which seems a little early for injector problems.  I of
course only run high-grade premium.

Any theories before they try to replace or service everything under the
hood?

Thanks,

Jim Walsh
jimw@domain.elided

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