I have a 1997 bmw 740i. Check engine light came on (matco tool read multiple misfire code on #1, 2, 3 & 6 cylinder). Exhaust has white/blue smoke pouring out.

Multiple misfires usually are caused by a bad crank sensor, some times it can be a bad cam sensor but that usually does not go bad.

Hi bmuller,

While the engine is running, slowly remove the oil fill cap. If there is a heavy vacuum pulling against the cap I would suspect a failed crank case vent valve. If the valve has failed the most common signs are a rough running engine with misfires and smoke out the tail pipe. If this is not the case, try clearing the faults and running the engine without the air mass meter connected. The air mass meter on this particular engine management system is the second weakest link.