89 Audi 90 stumbling

[Grant Lenahan]

sounds like an O2 sensor to me, btu you replaced that.

Are you sure the new one is good?

Next would be some odd fault in air metering - the other half of  
mixture control

Grant
On Jul 3, 2010, at 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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