89 Audi 90 stumbling

[Tony Hoffman]

Have you checked all the intake hoses and the air intake boot?
Difference when turning is what makes me think it might be related.
Also, how are the cap and rotor? Is the cap on securely, and with no
cracks? How about the Hall sender plug? Secure, or perhaps rubbing?

Tony

On Sat, Jul 3, 2010 at 7:22 PM, Mark Rutherford
<mark.rutherford at emerytelcom.net> 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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