89 Audi 90 stumbling
Huw Powell
audi at humanspeakers.com
Sun Jul 4 15:48:03 PDT 2010
On 7/4/2010 10:20 AM, Mark Rutherford wrote:
> Changed the ECU with the one from the parts car. The behavior of the car
> did not change. However the check engine light did start working at this
> point. What pointed you to a bad ECU on your car. Is corrosion on the
> terminals a problem on the 90.
My bad ECU was a long time ago so I don't really remember, but the
diagnosis would either have been a quick test at the pressure actuator,
or a simple "swap and see".
The corrosion problem I have is rather unique - I never truly "swapped"
the ECU, I just left it hanging by the harness/connector. Then when my
heater core let go this spring, some of the coolant ran down the wiring
and into the connector. There's just one socket that looks icky, and I
now have to start it two or three times when its warm (!) to get it to
run properly.
But I don't really care to fix it since I'll be porting over to a "new"
one as soon as I get its sunroof closed... oh yeah, that reminds me, I
need to post a question about that...
Oh, and try unplugging the knock sensor. What are the exact stumble
conditions?
> Thanks
> Mark
>
> -----Original Message-----
> From: Huw Powell [mailto:one at humanspeakers.com]
> Sent: Sunday, July 04, 2010 12:12 AM
> To: Mark Rutherford
> Cc: quattro at audifans.com
> Subject: Re: 89 Audi 90 stumbling
>
> ECU connection? ECU bad? (btdt)
>
> On 7/3/2010 8:22 PM, Mark Rutherford wrote:
>> I have a 1989 Audi 90 that has developed a hesitation. I own several
> Audi's
>> and have done all of my own repairs for over a decade. However on this
> one
>> I am stumped. I hope the group can give me some ideas about where to turn
>> next.
>>
>>
>>
>> History:
>>
>> About 5 years ago I install a manual transmission to replace a failed
>> Automatic. Drove the car for about a year no problems. The car sat for
>> about 4 years after that. This spring I decided to sell the car. To get
>> the car started I installed a old fuel pump I had, and fixed a vacuum lead
>> in the intake boot. Car ran fine for about a month.
>>
>>
>>
>> Symptoms:
>>
>> Car will be running fine and then loose power and shake under acceleration
>> then recover and run fine. The problem has become more frequent with
> time.
>> It will not do it when it is cold but will start to before it reaches full
>> temperature. It will happen repeatedly when making a right turn. Will
>> sometimes do it when driving straight. Rarely does it turning left.
>>
>>
>>
>> Repairs done so far:
>>
>> When investigating the problem found that there was no bulb in the check
>> engine light. Installed one and tried to pull codes. Check engine light
>> will turn on when jumping diagnostic connector, but will not flash codes.
>> Placed LED in diagnostic connector with appropriate resistor, no codes.
> Put
>> a volt meter across the connector and found the ECU was producing codes
> but
>> at a voltage of 1.5 volts, I do not know if this is normal for this car
> but
>> I do not believe it is. Also noticed small unchanging voltage from o2
>> sensor ( .2 volts ). Adjusting the mixture produced no change in o2
>> reading. Replaced o2 sensor. No change in problem or o2 readings.
>>
>>
>>
>> 1. From the pulses on the volt meter found a code for the knock
>> sensor. The insulation on the cable was rotted away and in general bad
>> condition. Replaced with new sensor torqued to 22 Nm. No change in
>> problem, ECU produces 4444
>>
>> 2. The used fuel pump was making noise, replaced with new one, no
>> change. Also replaced fuel filter. Read an article in the archive about
> a
>> strainer on the fuel head that can become plugged. Removed it per archive
>> suggestion. Still no change in problem, ECU 4444. The car will run fine
>> under full load in high gear up hill for several minutes. This leads me
> to
>> believe the fuel system is capable of delivering the amount of fuel
> needed.
>>
>> 3. Since I have a parts car I changed.
>>
>> a. The coil, No change
>>
>> b. Installed additional ground wires from the battery to the intake
>> manifold, engine, body and bell housing.
>>
>> c. Coolant Temp sensor - No change
>>
>> d. Fuel distributor including - No change
>>
>> i.
> Fuel
>> head
>>
>> ii.
>> Potentiometer
>>
>> iii.
>> Differential pressure regulator
>>
>> iv. Fuel
>> pressure regulator
>>
>> e. All of the o2 sensors I have seen produce a voltage that changes
>> from about .4 to .6 volts. This one produces a steady voltage between 0
>> and .5 volts depending on the mixture. Adjusting the mixture full rich
>> until the motor dies still produces a reading of .5 volts. Install a new
> O2
>> sensor same results as above. The above happens plugged in on not. This
>> part still makes no sense to me.
>>
>> f. Changed ignition computer - No change
>>
>> g. Changed fuel computer - no change in problem , but the check
> engine
>> light works as it should.
>>
>> h. Checked wiring from All data CD and diagnostic procedures. No
>> problems found.
>>
>> i. The car had a exhaust leak, thought that it could be pulling in
>> air and effecting the o2 reading. Repaired the leaks - problem still
>> there. O2 still behaving strangely.
>>
>>
>>
>> I really do not know where to go next. Only things out of the ordinary
> are
>> O2 sensor reading, and check engine light with original computer. I have
>> not check fuel pressure, due to lack of tools.
>>
>>
>>
>>
>>
>> Thanks for any help
>>
>> Mark Rutherford
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
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>>
>
--
Huw Powell
http://www.humanspeakers.com/audi
http://www.humanthoughts.org/
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