Cold Start Stumble

Phil Rose pjrose at
Thu Mar 23 20:41:50 EST 2006

At 4:18 PM -0800 3/23/06, Rich Letsinger wrote:
>Howdy. I'm a new poster to this list and have an urquattro with a 3B in it.
>I'm running factory engine management with everything except the after-run
>pump hooked up as it would be in a 200.  On cold startup the car stumbles to
>life, barely turning any RPMs at all until I blip the throttle.  Once the
>RPMs have exceeded 1K or so she runs perfectly, doing the normal warm-up
>cycle stuff and then settling down to the 850 RPM idle.  All other bahavior
>is normal include warm restart.
>The bypass is new and I've just finished weeding out any vacuum leaks.  I
>cleaned the ISV with carb cleaner and it seems to work correctly in every
>situation except cold start.  It never used to have this problem, started a
>few months ago and has been getting gradually worse.  Are there any other
>things to check?

I recall (maybe incorrectly) that one source of rough running during 
warm-up can be from a bad intake-manifold air temp sensor. One thing 
to check--at a minimum-- is that the wiring to the sensor contacts is 
good. I believe the only way to do a valid resistance measurement for 
that sensor is to remove the ECU connector (see Bentley).


Phil Rose
Rochester, NY
mailto:pjrose at

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