poor warm start + engine racing - 5kcstq

[Ben Swann]

Troubleshooting combined 5ktqw warm start problem compounded by ISV open on 
startup(engine racing).  Problem started as a warm start problem getting 
progressively worse(perhaps because spring weather is here).

Car always starts right away cold.

After engine warmup complete, come back in 10 min - 1hour and car will not 
start.  Set a few minutes and fires right up.

No vacuem leaks.  New injectors. Timing belt, etc done recently.  Ran some 
BG44K through a couple weeks back.  Worstening problem has prompted me to 
start troubleshooting. I didn't watn to get into fuel pressure/leakdown 
tests - yet.

Now here is what I messed with - my Audi certified tech friend insisted it 
was the pressure relief valve(and not the warmup/control pressure regulator 
as I had suggested).  I removed the assembly  pressure relief assembly and 
saw nothing visibly worn or dirty, cleaned thouroughly and replaced. 
 O-rings were in perfect condition.   I allowed the system to run fuel out 
the hole prior to reinstallation.

After that, the car started and idled very slowly around 500RPM and I 
adjusted throttle screw to 800RPM.  Engine ran fine.  Revved several times 
to make sure engine idle stable and allowed the engine to warm up.

I shut off and restarted, and the engine revved to ~2500RPM - what the!.  I 
could not adjust down with throttle screw, but was able to drop idle by 
disconnecting ISV.

Duplicated situation by reconnecting ISV, shutoff and restart then high 
RPM.  I don't see how anything I did could effect the ISV operation, so is 
this a coincidence?

After engine cooled down later, it started with great difficulty, but I did 
not have the ISV problem repeat.

Any clues - please don't suggest it is a defective ISV, unless you are 
quite certain - I have a spare I can swap out with to be sure.  To me it 
would seem more like the ISV control unit or circuit is on the fritz, and 
may be contributing to the warm start problem too.  Just looking for some 
leads.

TIA.

Ben