4kq runs rough when cold

Adam P. Brodeur AdamB at net1plus.com
Mon Nov 27 12:51:57 EST 2000

I agree with Huw on this.  Your problem sounds very similar to the one I had
with my 84 4ksq.  I don't have the specs for the temp sensor as I'm at
school and don't have the Bentley manual.  Test that first.  If that is
alright, make sure that the computer is in circuit.  That was my problem.
The 10A fuse in the computer was blown.  Don't know how, but that fuse made
the car run like sh*t.  I also replaced the temp sensor, about $35 from Blau
because it wasn't in range, probably another problem waiting to happen.  If
the sensor is orignal, replace it so that the computer can get accurate
readings.  My car runs much better after a new sensor, complete tune up and
yes, a 10A fuse.

Adam Brodeur

-----Original Message-----
From: quattro-admin at audifans.com [mailto:quattro-admin at audifans.com]On
Behalf Of Huw Powell
Sent: Sunday, November 26, 2000 11:32 PM
To: Greg Rich
Cc: quattro at audifans.com
Subject: Re: 4kq runs rough when cold

most likely the temp switch on the underside of the top coolant hose -
tells the ecu engine temp so it can compensate for cold conditions with
more air and fuel.  I forget what its resistance values are suppsoed to
be cold/hot right now but I'm sure someone else could find it in their

> 1986 4000 S quattro, 5 cyl, non turbo,
> 1.Starts fine, hot or cold, cranks and fires rigth away
> 2.After running a few seconds it will start to miss (idle)
> 3.After running a couple minutes it will stall (idle)
> 4.If I try to drive it will buck and miss and be a really difficult to get
> to highway speed
> 5.After running 15 minutes it will run like a champ, then once in a while
> fire
> I have unplugged various sensors and switches but cannot fool it. It will
> however run quite well when the full throttle shut is making contact
> rich).

Huw Powell



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