'87 5KCSTQ reluctant to start cold

[patrick gillen]

John:
This winter under cooler weather (we don't get cold in western Oregon), my son's '87 5000CST starts right up when cold but will not start easily when hot; it usually needs to cool off but he usually strategically parks it to compression start it. We did that the other day when out an about and it stunk of unburned fuel when it got going yet the tail pipe runs pretty clean. It is hard to suspect vapor lock as it didn't do this all last summer. 

Another thing I noticed is the idle varies, running a very lumpy minute at 900, then a smoother minute at 1100, repeat. I haven't been able to rule out the A/C compressor cycling changing the idle even though compressor is bad and I think disconnected. The timing mark does change maybe 5 degrees on the changing idle speed but is pretty steady at each position. Unplugging the aux air regulator makes no change in the idle.

I too am baffled; are these your symptoms? I can't tell from your descriptions below.

My feeling is this somehow includes the turbo controls as it doesn't seem as neck snapping as it did last summer compared to my old non turbo 5000. Don't get me going on how they managed to completely bury that turbo from any possible maintenance and I also need to understand how the whole turbo bypass system works which is at the south end and buried under a bunch of plumbing on top.

Pat

-----Original Message-----
From: John Larson [mailto:viejoloco at comcast.net] 
Sent: January 07, 2015 5:05 PM
To: quattro at audifans.com
Subject: '87 5KCSTQ reluctant to start cold

While I've been retired and Audiless for a couple of years, I still have a couple of friends with elderly Audis and they rely on me for service help.  In this case, it's a problem I never encountered while I was wrenching.  Hot start, pretty often; cold start, never. Once the car sits and becomes completely cooled off, it takes an extended period of time to get it to start (like 1-3 minutes of fiddling).  Giving it even the slightest throttle makes it worse. Once it's up and running, no problem, and it runs really well.  The cold start valve works, although I didn't time it, the control pressure is under 2 BAR in 75+ degree weather today.  System pressure is within specs, too.

Before I dive into this, anyone here inclined to give some informed commentary?

Thanks for your time.
John.