Barely-running '89 90q

[DePenning, Charles [EPM/MTN]]

I've tried the OXS both grounded and ungrounded, neither seems to make much
difference.  I don't know where I got the idea to ground it.  It did make
the dpr current stable though.  

I am back to the ignition, since I haven't seen anything on the fuel side
yet.  Timing is done by the 'puter on this car, but is it possible to have a
bad control module or hall effect sensor and have the car still run, albiet
crappily?  I have had both items fail on a 4kq, and it just wouldn't start.
Then I think about my cam/crank indexing.  I did check the reference marks
on the cam gear and the flywheel (they lined up), isn't that all there is to
it?  I am getting hot spark to all five cylinders, so I am happy with the
cap/rotor.  It doesn't seem like there is much else in the chain to go
wrong.

I am looking forward to my trip to the Canyonlands of southeast Utah on
Tuesday.  Maybe I can outrun that nasty gremlin while I'm out there.  Thank
goodness I have a Jeep! 


Charley

'89 90q
'84 4kq
'83 5kT
'01 Cherokee  <-- gremlin-free canyon cruiser 

 
-----Original Message-----
From: Huw Powell [mailto:audi at humanspeakers.com] 
Sent: Monday, April 05, 2004 1:16 PM
To: DePenning, Charles [EPM/MTN]
Cc: 'quattro at audifans.com'
Subject: Re: Barely-running '89 90q


> Thanks for the guidance Huw.  Unfortunately nothing seems to be
> malfunctioning- I must be still missing the gremlin, or he is quick 
> and invisible.  Temp sender good according to Bentley specs, fuel 
> dist. pot good (I knew that 3 wire harness connector from the junkyard 
> would come in handy someday!), both WOT and idle switches work as 
> expected, dpr current measures good (100 mA w/o engine running, down 
> to 10 mA for the 'functionality' test when the WOT switch is closed 
> and the engine is stationary, varying current with engine running, 
> tracks with O2 sensor installed, steady with it unplugged and 
> grounded)

the dpr current is supposed to oscillate around 0 mA, up and down a few mA,
with the engine warm and running, at idle.

If you unplug the OXS there is no need to ground it.  If you ground the
signal wire to the ECU, teh ECU will overreact and try to compensate.

> O2 is all over the place, but unplugging does not remedy the 
> situation.  CSV ok, unplugged it with no change, grounds good and air 
> filter clean.  WTF?
> Is it possible to send a steady 0.7v to the computer in place of the 
> O2 sensor voltage (fake it out)?

If you simply unplug the OXS, the computer has a 0.5 volt reference of its
own that will allow the engine to run at the static mixture setting.

A working OXS should oscillate up and down between about .2 and .8 volts
while the dpr is doing its thing (in reaction to the OXS cycling).

--
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/