88 80Q, Runs rough upon starting

[Eric Huppert]

SJ, Ben, Huw,

"Survey says" .... Thanks for the input.

Per SJ, Yes, when car is cold (as in morning) it starts and runs fine. Only
when car is warm, then allowed to sit for 5-10 minutes (or longer) does it
act up.

Did test the sensor (double terminal) last night when car was hot. But will
do the ice water and increasing temps when my son gets home after school.
Will probably pick up another sensor anyway...

Hoping this is throwing off the Diff pres reg values... And not quite
certain why the full throttle switch will illuminate chk eng light when
switch is actuated.. Understand that one sensor can throw everything off,
so, based on the temp effects/when problem occurs I'll go through that
first. Had noticed in the Bentley that the temp sensor actuates the
acceleration enrichment circuit also...

Gotta love electrical stuff! (If this was a 44 it would have already been
diagnosed! :o) When this car sells he's getting my 90 200TQ... Back to
familiar territory (besides the fact I dumped a ton of $'s into rehabbing
and sorting out, so most everything is done already!)

Thanks...

Eric

-----Original Message-----
From: SJ [mailto:syljay at optonline.net]
Sent: Tuesday, November 14, 2006 10:48 AM
To: quattro at audifans.com
Cc: dragracer at netstep.net
Subject: Re: 88 80Q, Runs rough upon starting


> From: Huw Powell <audi at humanspeakers.com>
> Subject: Re: 88 80Q, Runs rough upon starting
> To: Eric Huppert <dragracer at netstep.net>
> > If car is allowed to sit 5-10 minutes after shutting off, (or even on a
cold
> > start) upon restart car fires, then starts to stumble and drop RPM's.
> > Feathering gas pedal, etc, doesn't help. But, discovered that full
throttle
> > will get the rpm's up, but when let off it still runs rough. It clears
up in
> > a minute or two, but something's not quite right
> >
> > Thoughts, BTDT???? Sure this is a sensor issue of some sort and can,
(and
> > will) be easily fixed. Need to resolve this quickly!
>
> Sounds like the temp sender died - ECU thinks engine is already warm.  I
> think they run about $20 or so.  Remove and test with ice water/very hot
> water and your ohm meter per your Bentley specs.
>
> --
> Huw Powell

***** Yup. Sounds like the water temp sensor. Location on an NF engine -
between and above #1 and #2 spark plugs - the top sensor.

These are Resistance readings you should get when testing the sensor in a
pot of water over stove.
Start off with cold water and ice cubes in it.
Temp vs Resistance readings on my 90 100q temp sender.
deg F   ohms
35        4500
60        3200
80        2300
100      1360
150      510
207      203

Question: Does the engine ever start and run normally? Your post does not
mention that - only says 'restart'.

The symptoms might also indicate ignition cross firing - engine does the
funky chicken routine. The problem is due to carbon tracks inside the
distributor cap resulting in cross firing. It only crossfires when humidity
levels are just right . . low temp and high humidity resulting in a low dew
point - moisture condenses inside the distributor cap and bridges the carbon
tracks.
The symptoms will disappear once the engine (and dist cap) are warmed up.

Take off dist cap and clean the insides. I use fine steel wool, then
alchohol wipe down, followed by silicon spray and wipe off. Buying a new cap
is less work. Caps are pretty cheap.

SJ
85 Dodge PU, D-250, 318, auto
85 Audi 4k - - sold but still on the road
88 Audi 5kq
90 Audi 100q





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