1988 Audi 90 5cyl -warm idle & other problems

[Alan Pritchard]

This message is in MIME format. Since your mail reader does not understand
this format, some or all of this message may not be legible.
--
[ Picked text/plain from multipart/alternative ]
I intermiitantly get the same error code, usually when warming up, I turn
the ignition off and on and it clears, car performance also deteriorates
when this code is stored, it behaves properly after wards (1989 90 quattro).
The idle business I would supect to be relating to either timing or
fuelling, probably mixture  if the car bucks upon wot and idle so I would
check that first , remember timing and mixture must be set with the fp fuse
in. If you need further details on setting up idle co look in the Bentley,
or try sjmautotechnik.com, I think scott has the relevant articles up, if
not try huws site, im sure he has the info there.

Best Regards,
Alan Pritchard
Network Administrator



Tel.  01329 289000
Fax. 01329 289001
www.seaeye.com

-----Original Message-----
From: Chris Roden [mailto:chris.roden at cox.net]
Sent: Wednesday, November 06, 2002 1:39 PM
To: quattro at audifans.com
Subject: 1988 Audi 90 5cyl -warm idle & other problems

This is a multi-part message in MIME format.
--
[ Picked text/plain from multipart/alternative ]
Help - warm idle and other problems,
I have a 1988 Audi 90, 5 cyl, 5 sp, non turbo, with several problems. (this
vehicle has separate ignition and fuel injection computers)

The main problem is that once the car is warmed up, the idle is very poor,
usually very low around 300-400 rpm. If I insert the fuse into the top of
the relay, to dump the codes while the car is running, the idle will jump up
to where its supposed to be (700-900) and stay there until I remove the fuse
and then push on the throttle.  After that the idle will return to its
crappy state. Around 400 rpm.  (idle switch checks ok, and is closed when in
idle position)

I have 2 other issues, the first is occational stuttering while
accelerating.  This is not very pronounced, and does not occur all the time,
and is most likely to occur during very hard acceleration.  This is also an
issue that the car has had for a long time - 5years, in which time I have
replace, a fuel pump, an O2 sensor, a fuel filter, all for regular
maintenance. Lately it has gotten worse, and more pronounced.

The other issue is varying idle during warmup. During the warm-up period the
idle will vary between 2000 and 1000.  It will do this fairly rhythmically.
I put a timing light on it and noticed, that during the faster idle, the
timing was 12 deg. BTDC, and when the engine slowed to 1000 rpm, the timing
dropped to 6 deg. BTDC.  The timing seemed to continue varying with the idle
speed for 2-3 minutes while the engine warmed up, after which time the idle
usually stabilize, and then usually deteriates to the 300-400 rpm. This
issue is newer, and seemed to show up, when I started getting the 2232 error
code - airflow sensor pot.

I have not been able to clear the error codes, with any of the prescribed
methods, except removing battery power to the computer.  I have a spare
ignition computer, and it does not appear to make any difference, so I
assume it is OK.
The one code I always get is 2232 - airflow sensor pot.
I checked the voltage between terminal 3 and 1 while the unit was plugged in
and the ignition was on.  It was 4.85volts.  This value did not change as I
lifted the airflow sensor.
I have gotten some other error codes, but consider them suspect because of
all unplugging and testing I have done.  I did recently get the code about
the computers not talking to each other.
Here are some of the other items I have checked and their measurements.
Full throttle and idle switches both - 6 Ohms closed - infinite Ohms open.
O2 sensor voltage out once warmed up - 0.62 volts fairly constant (+- 0.02
volts).
Differential pressure regulator current is 100mA with the ignition on, and
before starting. After starting the current drops to 0.1 - 0.3 mA staying
fairly constant.
Dual temperature sensors 1690 Ohms cool (70deg), 380 Ohms warm.
Also the O2 sensor is fairly new less that 10,000 miles on it.

I have also checked some of the standards, Grounds at intake manifold are in
good shape. All fuses appear to be in their correct places, (2 engine fuses,
next to spare slots, actually have a red cover over them with the word
"Motor" on it).  No apperent vacuum leaks, but are there any areas that I
should specifically check?

Any help would be extremely welcome. I'm considering getting a used FI
computer from an auto recycler, but am wondering how robust these are, and
if a used one is also likely to have issues.
--