1983 Audi Coupe GT - Engine stalls on quick acceleration

[mwvogt at netzero.com]

Chris,
Here's what I hear you saying...

Car is cold... starts fine... runs fine.

Car gets warm to hot...it stalls.

Here's what I think.

COLD START INJECTOR...is getting the wrong signal or because of wiring it won't stop injecting.

AIR TEMP SENSOR...maybe thinking it's cold all the time and keeps doing what it's not supposed to when it's warm.

There's about 3 things that tell the CSI what to do and when and the first thing is to see if it still keeps shooting gas when it's not supposed to. 

Then, there's a temp sensor that runs from the block.

Then there's the small "dryer hose" (as I call it) that runs from the exhaust side of the block to the bottom of the air intake box to tell it if it's warm enough to run efficiently. Sounds stupid but once I found the parts and did that hose my idle smoothed out especially in winter. Maybe just dumb luck.

Sounds like you've replaced a lot of important parts along the way, always a benefit to that once you find the culprit.

Anyway, I'll keep thinking.

Mark Vogt

---------- Original Message ----------
From: AUDICPGT at aol.com
To: quattro at audifans.com
Subject: 1983 Audi Coupe GT - Engine stalls on quick acceleration
Date: Mon, 17 May 2010 17:07:22 -0400 (EDT)

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 kit, 
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 in  
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  similar 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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