MAC11 help needed

[Ado Sigal]

If you haven't changed fuel filters, now is the best time. Pre FP filter 
is always the first suspect. To test, swap PPF with 8 mill tube. If no 
better, change main FF. Anyway, similar symptoms on S2 where due to 
loose clips on flexi hose that connects EM and WG.

Good luck,

Ado

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>>patient is coupe quattro conversion (dedicated track car) with 10v turbo
>>(MC1 w/one knock sensor) motor. I can get the car started and running up 
>>to
>>2000 to 2500 RPM before it starts backfiring. Can hardly get up to 3000 
>>RPM
>>even with throttle floored. The flywheel "0" mark, the cam mark, and the
>>distributor mark all line up properly. If I move the distributor off the
>>mark (advance) while running, it will rev like normal, but won't start 
>>after
>>shutdown. I can move the distributor back to initial position and it 
>>starts
>>right up.
>>
>>I suspect that something is causing the timing to retard, but I have 
>>swapped
>>out the ECU, complete distributor, the cap and rotor, plugs, wires, RPM 
>>and
>>flywheel sensors. I plan to try another knock sensor, but can't figure
>>anything else that would cause a properly running engine to start 
>>backfiring
>>like this. BTW, after the problem, I took the opportunity to install my
>>newly rebuilt engine, and the problems are the same, so I can rule out
>>mechanical issues.
>>
>>I have been using the 034 Motorsport EFI, and there is no sign that it is
>>going lean or rich when this occurs. My fuel pressure (aftermarket FPR)
>>rises slightly as revs come up as I would expect with the start of boost.
>>Besides, the timing seems to be the thing that has changed, as evidenced 
>>by
>>the regular running after advancing timing.
>>
>>It acts as though the timing reference pin is in the wrong place, but it 
>>has
>>been running fine for 8 years and the problem came on gradually during 
>>some
>>rainy sessions at Watkins Glen in May. Thought something must have gotten
>>wet, but after swapping everything I can think of, nothing has changed.
>>
>>The pin is still on the front side of the flywheel, but it does not line 
>>up
>>with the pickup when the crank is at "0" and the distributor and cam marks
>>line up. Is this right?
>>
>>Any help appreciated,
>>Rick
>>Pulling my (gray) hair out!
>>
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