start up problems

[codger318]

At start-up my '92 318is will intermittently "backfire" (usually accompanied by an electronic "grinding" noise). This "backfire" is not in the exhaust, but intake system. This event will usually blow the j-shaped moulded hose off the Idle Control Valve. Most recently it blew up the rubber air duct between the air filter and throttle. I have changed the O2 Sensor (and the blown duct), but the problem has reoccurred.

Any ideas?

[parolof]

what an electronic "grinding" noise"???:-))

[codger318]

sounds like an electric motor (but is not the starter, or any other source I can think of)

[LiquidBMW76]

Sounds as if you are getting spark before the intake valves have a chance to close