Sorry for posting here, but I seem to have exhausted the Audi forums for help on this one. The primary question is of a general nature though...
What problem can be overcome by advancing the timing?
Background: Patient is a 1988 UK Audi 100 (with 2.0 5-cyl RT engine, K-Jetronic) which broke down 2 months ago. It is extremely difficult to start. If I can start it, then it will run for about 10-15 mins then cut out. Difficult to restart if turned off. Not driveable as stalls too easily. I can't find anything wrong aside from the symptoms. I have swapped the warm-up valve, fuel distributor & ISV for known good ones but no change. Cold start valve ok, idle switch ok, no vacuum leaks found. Plenty of fuel getting to the fuel distributor. Hall sensor ok - anyway I always get a spark.
Recently I checked the ignition timing and made an interesting discovery.
18° BTDC is the standard figure but I'm using regular unleaded for which I believe the timing should be 8° BTDC. However, I found that by advancing the timing to about 30° BTDC it will start on the 2nd crank instead of about the 30th! Initial testing suggests it's much less likely to cut out. Cam timing seems in order and all my TDC marks line up together.Can anyone explain what's happening?
Thanks, Gary