88 80Q won't start or idle when cold unless you crack the throttle

[SJ]

> From: MXHOWES at aol.com
> Subject: 88 80Q won't start or idle when cold unless you crack the
> throttle
>
> The car will not start when cold unless you press  down on the gas just
the
> smallest amount. If you crack the throttle, it will  start right up, if
you
> take your foot off it tries to idle at about 400  RPM.
***** That means your spark is ok and its an "air or fuel" issue.
"Cracking the throttle" means opening the mechanical throttle plates to let
in more air.

Why would you need more air? If the ISV valve is stuck in closed position,
you would need more air.
Or, if the fuel distributor air sensor plate is binding, you would need more
air  . .the extra air flow would pop the sensor plate out of its jammed
position. A jammed sensor plate will result in no fuel at the injectors.
Once the plate is popped free, it should float above the "jamming position"
on a column of air while the engine is running.

Your symptoms indicate a cleaning as the first diagnosis step. And, if you
are cleaning, you might as well clean the ISV valve, the throttle plates,
and the fuel distributor air sensor plate "throat" area.
Use carb cleaner or throttle body cleaner.

You have to relieve fuel pressure before cleaning around the air sensor
plate. Otherwise, there will be quite a bit of resistance to your trying to
lift the sensor plate by hand. Fuel pressure is used by the system to
provide a counterforce to the air going by the sensor plate. To relieve fuel
pressure, crack open the cold start valve feed line - either end will do.
Use rags to catch and soak up the gas.
With no fuel pressure, you can test for binding by lifting the plate with a
magnet. Plate travel should be very smooth and light - - no resistance.
Even with no binding detected, clean the throat area and edges of the sensor
plate anyway.


>When cold you can make
> it idle ok ~900 RPM by applying a little gas  by foot, the mixture is
correct
> because no mater how cold it is it idles  smoothly (with your foot on the
> gas).
***** This confirms that your problem is not a fuel metering(A/F) issue. The
engine is not getting enough air into the system without you "helping" with
the throttle plate.

>After a few minutes (or miles) you can  remove your foot and it will idle
as
> normal. When hot, just  hit the key  and it starts up right away.
***** Yup! After the car warms up, the ISV gunk has softened enough so that
the valve works correctly. There is enough thermal mass(the engine) around
that valve to keep it warm enough so that the engine will start up and run
fine all day.
When the car sits ovenight, the cold congeals the gunk and the valve wont
operate until the gunk warms up.

This type of problem usually shows up in cold temperature conditions.
I've had a similar problem - except it would occur AFTER starting up and
driving! The temperature got colder as I was driving. After 30 miles on the
highway, when I got to the Bridge toll booth and stopped to pay the toll,
the engine was doing its funky chicken routine and would not idle right. I
pulled off at the exit right after the the toll booth. The car would not
idle unless I had the throttle cracked.
I shut off the engine, and sat there contemplating my doom. After 15 minutes
of crying, I started the engine and all was well, the engine idled fine . ..
what the hell?!
I turned around and went back home with no further problems. The temperature
by this time had risen. I left before dawn when temp was 12 F, and was
returning after the sun was up and temp was 25 F.
That day I took out the ISV valve and cleaned it thoroughly several times.
For the next several days, I tested the car under the same temperature
conditions. No problems. Yeah, I got up before dawn, started the car and
went on the highway. I did this over several days to confirm the fix.
I havent had that problem for 6 years now.
My original post on the problem at
http://www.audifans.com/pipermail/quattro/2000-December/011783.html

A fellow lister, Tony Lum, provided the following private response to my pos
t, which solved my problem:
"Problem with the Idle Stablizer Valve (ISV) or connections to it.  Remove
it and spray with carburetor cleaner till it runs clear.  Check the
electrical contacts on the ISV and the cable harness and clean with
electrical contact spray.  Final coat with Stabilant 22A if you can find
some.  The control for the ISV is in the auxiliary relay panel in front of
your left knee.  Its the double wide relay at the bottom left side of the
panel.  Remove and check contacts for any signs of oxidation.  At -12
degrees all contacts have to be perfect for correct operation."

When you fix your problem, send a post to the list telling us what you did.

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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