1983 Audi Coupe GT - Engine stalls on quick acceleration

Tue May 18 06:21:28 PDT 2010

Sounds to me like an A:F issue.  I gave the text here a quick read and didn't see mention of the O2 sensor.  If it has or hasn't been changed there could still be issues.

Put a multimeter on the O2 sensor wire and see what it reads.  A cheapie anaolg works best for this.  0 to 2VDC range.  Once warm the signal should fluctuate.  If it shows a constant value then the sensor may be shot.  If it does appear to fluctuate then check the CIS system Zero and Basic settings (sensor plate height) and fine tune from there.

If the O2 signal is pegged high then the CO adjustemnt may be way out of spec.  This happened with the coupe I picked up from Hayes.  The CO was adjusted to chase a failing O2 sensor.  Once I adjusted the CO to a reasonable value she ran perfectly.  It all depends on how or if the O2 sensor is failing/failed.

HTH.

--- On Tue, 5/18/10, dgraber460 at aol.com <dgraber460 at aol.com> wrote:

From: dgraber460 at aol.com <dgraber460 at aol.com>
Subject: Re: 1983 Audi Coupe GT - Engine stalls on quick acceleration
To: AUDICPGT at aol.com
Cc: quattro at audifans.com
Date: Tuesday, May 18, 2010, 9:05 AM

Christopher;
Don't give up yet. I have often been where you are and this list (especially Huw) talked me off the ledge.
I have the JC Whitney gauges you are welcome to borrow if you like. Just promise to send them back.
You have done a good job of narrowing down the suspects. You are close to outing the accursed culprit.
Do the plugs look lean or rich after the problem?
Let me know if you want me to send the gauges. (and where to send them)
I might have some parts that would help as well. I will check my stash tonight.

Dennis 
Denver

-----Original Message-----
From: Huw Powell <audi at humanspeakers.com>
To: AUDICPGT at aol.com
Cc: quattro at audifans.com
Sent: Mon, May 17, 2010 5:37 pm
Subject: Re: 1983 Audi Coupe GT - Engine stalls on quick acceleration

It's CIS-E, right (aluminum fuel dist. body)?
It's an unlikely thing to cause this, but check the WOT switch for 
unctionality.
Another unlikely thing to consider is to check the throttle bits to see 
f any are doing something weird, like, say, shorting out a worn wire, 
r opening a vacuum leak.
Btw, that engine/system shouldn't stall when the oil cap is removed.
Also, since the engine "rotates" a bit on its mounts when you floor it, 
t could be opening up an intermittent vacuum leak, under the big intake 
ose thing, for instance.  What kind of shape are your engine mounts in?
AUDICPGT at aol.com wrote:
1983 Audi Coupe GT 2.2L I-5  Miles = approx. 220K

What started out as a random issue has now become a constant problem... as  
follows:

Engine starts fine cold, idles fine also.  Upon quick acceleration,  engine 
cuts-out, as if complete loss of fuel pressure, ignition spark or  engine 
vacuum dropping the fuel metering plate.  If I stay in the pedal,  the engine 
will die... if I jump off the pedal and feather it, it will stay  running.  
On very easy acceleration, it will rev up normally to the  redline.

I checked all my vacuum lines for leaks - cracks - looseness, sprayed some  
starting fluid around connections... all seem fine, no spikes in idle.   
Removing oil filler cap does make engine die.

I suspected plugged up fuel filters since I have been there before on  
another vehicle of mine.  I knew it had been at least 5 years,  so I replaced 
both filters, and also my fuel pump that has been louder  as of late since 
everything was disconnected anyway. I don't have a CIS fuel  pressure test 
it, 
so I had no problem shot-gunning these replacements.   Also, while I had 
the filters disconnected, I checked the free-flow out of the  fuel tank... it 
was strong, no obstructions there.

Testing upon reassembly = No change!

I was advised to replace my fuel distributor (it had been seeping), so I  
did w/ a rebuilt unit from Python.

NO CHANGE!

I suspected stuck open fuel injectors causing fuel pressure drop in  
distributor... so, since I had never had them cleaned I decided to take them 
n  
to Doctor Injector.  The guy said that they were gunked up, but sprayed  fine 
now.  I was optimistic.

Reinstalled injectors (new seals too) = NO CHANGE!

I wanted to check and see what happens with spark during the event.  I  
hooked up my timing light, find steady strobe on idle... rev'd up the engine  
slowly, strobe sped up normally.  From idle, quickly opened the throttle,  
the strobe sped up, and when engine cut-out the strobe continued to  pulse... 
SO, I surmised that the ignition system is NOT the  issue.  Spark is being 
generated at time of stall.

I next considered waving the white flag and taking it to a shop  that had 
the proper fuel system diag equipment I didn't have... BUT  FIRST...

Years ago, I had another car that the Cat convertor disintegrated &  
plugged up, creating huge back pressure to the engine.  That car acted  
imilar to 
my GT's problem, and I wondered if this was the case, it could be  causing 
back pressure that would affect the fuel metering plate.  I  disconnected 
the exhaust to inspect the Cat... it looked fine, I could easily  see right 
through it.  Discouraged, I decided to run open-header to  eliminate any 
questions about the entire exhaust system...

NO CHANGE!  Engine roared to life, idled fine, BUT cut-out on the snap  
accelerations!

At this point I've reached that PUT-A-FORK-IN-ME-I'M-DONE stage.  I  feel 
beaten (which rarely happens to me with my vehicles).

I found this forum, and decided to give it a shot before limping it to the  
shop.  The old GT has been a reliable commuter (keeping miles off my  
Infiniti G35 Coupe), so I can only hope it is something simple I have  
overlooked, and not expensive as to be cost prohibitive in fixing.

I thank you for withstanding my saga, and also for any ideas you may have  
for me.

Christopher

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-- 
uw Powell
http://www.humanspeakers.com/audi
http://www.humanthoughts.org/
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