Audi 100 Won't Start

[Marc Boucher]

My otherwise reliable Audi 100, 1990 has finally let me down.  (CIS-E-III, 
NF engine, non-turbo, non-quattro, automatic)

I've owned the car in California for over 4 years and its been fairly 
reliable with only routine maintenance required.  Almost a year ago I moved 
up to eastern Canada and its also been trouble free, including through the 
tail end of last winter.  Never gave any trouble starting or running.  Its 
kept indoors in a garage heated to about 10C (52F).

A few days ago we set out to the store.  It started ok but about 1/2 a mile 
down the road it died and would not restart.  Battery is fine, turns over 
fine, runs for 1/2 second then dies, in other words it tries but never quite 
reaches a stable idle.

We pushed it home and almost 3/4 of the way home we tried again and managed 
to get it started again and I parked it underground.  I've left the battery 
on a trickle charge to make up for all the attempted starts.

Right now, it will only start after several attempts and then die.

I performed the input and output tests as listed at this site:
http://www.sjmautotechnik.com/100ecuf.html

and pulled the codes.   Here are the results (in order as they appeared) and 
their meaning:

INPUT TESTS:
2232 Air Flow Meter plate rotary Potentiometer defective, check sensor 
output and system wiring
2232 Air Flow Meter plate rotary Potentiometer  defective, check sensor 
output and system wiring
0000 End of Diagnostic Output
1231 Transmission speed sender (G68), Signal used by Ignition Control Unit 
(ICU), check sensor output
2411 Exhaust Gas Recirculation Valve, (California Vehicles only)
2132 Data Wiring Defective, check wiring (California Vehicles only)
2132 Data Wiring Defective, check wiring (California Vehicles only)
2132 Data Wiring Defective, check wiring (California Vehicles only)
2132 Data Wiring Defective, check wiring (California Vehicles only)


POTENTIOMETER CHECKS OUT OK:
I checked the potentiometer.  It moves freely and is centered within the 
venturi when at rest.  The resistance between the bottom and the middle 
contact is about 2 kOhms at rest and rises to a max of about 13kOhms near 
full open falling slightly to 11kOhms at full open.  The resistance between 
the bottom and top contact is a constant 4.4kOhms.  The resistance between 
the top and bottom contact is 5.5kOhms rising to about 11kOhms near full 
open then falling slightly to 8kOhms at full open.  From what I've read this 
appear to be functioning correctly.

NO APPARENT VACUUM LEAKS:
I've searched the hoses and they seem in good condition.

OUTPUT TESTS ALL PASS:
Tests of Differential Pressure regulator, Carbon Canister Solenoid, Idle 
Stabilizer, and Cold start valve all perform as expected.

I changed the fuel filter and added two bottles of gas-line anti-freeze to 
the tank (tank has been at least 3/4 full anyway).

I checked all fuses and all are good and none are missing.

I erased the codes from the computer (California version has a memory that 
can be erased).

I performed a cursory check for any loose wires.

I started the car again (after many tries).  It ran smoothly (I had to keep 
it at 2000 rpm) for a few minutes.  Exhaust was thick white smoke which is 
probably a combo of rich mixture and the -25C air its exhausting into.  
After a few minutes it died (perhaps I let the idle drop a bit).  No 
restart.  At this point I pulled the codes from the computer again.  This 
time the following codes, in this order were pulled:

4444 No Faults have been recorded.
0000 End of Diagnostic Output
2132 Data Wiring Defective, check wiring (California Vehicles only)
2122 Engine speed sensor signal missing
2123 Full load/full Throttle switch Switch open ckt, stuck closed
2121 Idle switch Switch open ckt, stuck closed

A couple of other notes...the one problem this car has had since I bought it 
has been inconsistent electrical problems.  Interior lights will stop 
working for months, bulbs and fuses check out, and then they start working 
again.  This has included the trunk light, the under the hood light, and 
some interior lights.  Speedometer once cut out then came back next day.

I've checked that the ECU is firmly grounded, as is the intake manifold.  
I've read that I should check the grounding of the potentiometer, but 
neither that nor the fuel distributor appear to have been designed to be 
grounded as they're installed on top of the plastic air cleaner.  I also 
think that both are made of a non-conducting metal.  Strangely the fuel 
filter doesn't appear to be grounded, in fact there is a constant 10kOhms 
between it and ground.

Obviously I'm way out of my depth right now but I'm not quite prepared to 
take it to a mechanic yet, at least not without pointing him in a certain 
direction.  The problem is despite all my investigations I don't have any 
more of a sense of the likely problem.  Right now I'm thinking it could be 
any of the following: Bad Fuel-Injection Control Unit; Bad Ignition Control 
Unit; Bad Fuel Pump; Bad Fuel pump check valve; Bad Fuel pump relay;  A lose 
wire or connection somewhere leading to either ECU or between them; or any 
of a number of things.

I'd really appreciate any advice or any guesses at what the most likely 
causes might be.


Thank you,

Marc

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