1983 Audi Coupe GT - Engine stalls on quick acceleration

Mon May 17 16:31:51 PDT 2010

> Here's what I hear you saying...
> 
> Car is cold... starts fine... runs fine.
> 
> Car gets warm to hot...it stalls.

No, he's saying it starts fine, idles fine, and mild acceleration is ok, 
hard acceleration makes it bog down and die.

> Here's what I think.
> 
> COLD START INJECTOR...is getting the wrong signal or because of wiring it won't stop injecting.

Easy to test by unplugging it.

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

No such device.

> 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.

Which may be an issue, can be removed and tested in ice water/boiling water.

> 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.

All that does is supply slightly warmer air while the flap is closed. 
It doesn't "tell" the ECU anything.

> 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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