re: '91 200: Minor surging when warm

[pjrose@servtech.com (Phil & Judy Rose)]

Is the surging at _idle_ or at constant throttle running? If at idle (+/- a
couple hundred rpm), suspect the idle stabilisation valve (ISP) located
above the throttle valve. ISP could be sticking (in need of cleaning) or
have a bad electrical connection. If the surging occurs at constant
throttle, suspect a faulty O2 sensor.

Non-functioning or intermittancy of the temp guage is usually a symptom of
a bad "multifunction thermoswitch", which is the one you referred to. Sorry
I don't have part number available, but I'm sure you can get one at either
Chris Miller's (or Scott Mockry's) websites. From a Bosch dealer a
replacement is around $40-50. Sometimes worth a try to pull off the
connector and clean contacts.

HTH

Phil Rose



>Date: Thu, 1 Oct 1998 11:42:48 -0400
>From: "EREC - Duncan, Cameron" <CDUNCAN@nciinc.com>
>Subject: '91 200:  Minor surging when warm
>
>1.      My engine exhibits a slight surging that increases a bit when the
>engine has warmed up in afternoon rush-hour heat.  Distributor & rotor look
>okay, have about 15-20k miles on them.  Replaced a couple of vacuum hoses
>which improved starting and performance, but still have the slight rolling
>surge. I have some Techron I've been meaning to put in the tank at fill-up.
>Used some last Spring, but didn't see much change in engine smoothness.  Any
>ideas on what I should do to find the problem?
>2.      The temperature gauge also does not appear to engage but
>intermittently.  I understand I should perhaps replace a brass-encased
>"switch" that corrodes due to its odd mount (part name? Number?).  Could
>this be partly responsible for the surging?  Anything I should change while
>replacing or cleaning existing gizmo?
>
>Temporarily Bentleyless,
>
>Cameron Duncan, EREC Architect  -       (800) 363-3732  -
>CDUNCAN@nciinc.com
>Audi 200t sedan - daily driver

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