Rough Running 90q

[DePenning, Charles [EPM/MTN]]

I did disconnect the OXS this weekend- no change.  I measured OXS voltage
with the car stumbling along (fully warmed up) and it looked like it was
attempting closed loop control- oscillating voltage moving a little too fast
for me to really know what was going on (need to increase the sample rate,
Mr. Nyquist).  I need to hook up my scope to really take a look, but the
fact that it ran the same told me pretty much all I needed to know.

So I took the injectors out and gave 'em a squirt- wow, neat gasoline
needles shooting out of these things!  Unfortunately, that doesn't burn real
well, so I've got five of those on the way from Blau, plus the kit of
inserts, because I just KNOW those will break (BTDT on the '83 5kT).  A wee
brittle by now.  

Hopefully I found the problem.

Thanks for the help,

Charley
 
-----Original Message-----
From: Huw Powell [mailto:audi at humanspeakers.com] 
Sent: Monday, March 22, 2004 11:43 AM
To: DePenning, Charles [EPM/MTN]
Cc: 'quattro at audifans.com'; 'syljay at optonline.net'
Subject: Re: Rough Running 90q


> I wonder how bad a faulty OXS would make the car run?  If the signal 
> is bad from the Lambda sensor, doesn't the ECU go into failsafe mode?  
> Something like 50% duty cycle or basically open-loop control?

It all dpends on what is wrong with the OXS.  If it sends a constant, say,
0v or 1v to the ECU. the ECU will respond by running the car as fully rich
or lean as it can, trying to get the voltage back to 0.5v in vain.

If you *disconnect* the OXS, the ECU will read it's own internal 0.5v that
is there on the circuit by default, or as a comparator voltage or something,
and run the car at the basic static mixture that is set.

Which might let the car run "ok."

Why not measure the output voltage of the OXS with the car running and the
OXS hooked up?

--
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/