[Es2] Sport Quattro problem

[c cohen]

You guys have been kind enough to help shed some light on the mysteries of the KW engine in the light of your terrific AAN et al performers.  I wonder if you would take a look at this problem and tell me what you think.

Starting in the Spring, it would occasionally run rough - as if it was only running on 3 cylinders, but this was not the case.  More like cutting out momentarily - would not accelerate but could maintain speed with very light throttle.  You feel like going to WOT but you know it will probably die before you get there.  Then just as suddenly as the symptoms started, it cleared up and ran normally.  This happened in daylight (no lights) dry but around 28C with the A/C running.  I switched off the A/C but that did not help.  the shop I work with in TX thought it was the diverter valve and replaced it with one for a TT. the problem did not return but the car was not driven as regularly after June.

In September, after a 300 mile run, 4 track runs and 275 miles home, all flawless, the problem started again.  This time it got so bad that when I stopped for a light, it stalled and would not start. There was spark (checked) but a seemingly no fuel was getting through.  The A/C was on but I had switched it off well before it stalled.  I had just refilled and thought it might be bad gas.  I got a tow to the other side of the intersection and started calling for another tow.  After 15 minutes of phone calls, I turned the key, yet again, and its started, ran smoothly as if nothing had happened and home I went.  Warm dry day, 27-30 deg. C.

Later in the same month it happened again but this time it did not stall and cleared itself up after some nursing.  I then put in a bottle of the Chevron injector cleaner.

Two weeks ago, I drove a round trip in driving rain with and without A/C, 20-25 deg C.  No problems.

On Friday I drove it to work (30 miles round trip) and  as I pulled into my garage that evening, it started running rough again.  Tried to keep it going, played with all the electrics - but nothing made a difference.  It was hunting, revving to 2000 then dropping to near stall, then back to 2000 until it finally stalled.  Cold dry day around 14 deg C.  Once it stalled I could not restart but smelled unburned fuel.  The next morning the car started as normal - ran smooth.
I am guessing it might be something to do with the fuel pump but it is not noisy; or filters, which were changed last year.  There is no workshop manual for this car but I do have the calibration numbers for the various sensors but do not know where to start.

One suggestion has been the fuel return or the accumulators?

Anyway any ideas would be appreciated.

Colin