Posted by Neil Curry on January 12, 2001 at 12:19:53:
In Reply to: backfire revisited posted by MarcMc on January 12, 2001 at 02:13:24:
When a car backfires, especially on heavy acceleration, the main reason is that too much fuel is being pumped in (too rich). Running a car too rich causes carbon build up in the cylinders which also causes backfires. the carbon deposits heat up and cause the fuel to preignite before the intake valve is closed.
A car can run rich for many reasons. Its hard to say exactly what it may be from my point of view, but you can figure it out by eliminating different reasons and coming down to the main cause. Some times there is no one cause, it's just an accumulation of all causes.
You should check the air filter (not cloged), and timing (adjust by hand to get fastest, smothest idle with vacumm disconected). You want to run it fast and lean to burn off carbon build up.
Try these and report back!
Neil ('78 530i)