BMW 1990 535 rough idle and missfires under load

[louidesc]

Just bougt this 535 6 months ago...run great untill couple days ago.

I can starts pretty when cold, but the idle is rough, sounds like its running on 5 cyl. Tap on the gas litely and goes back to 6 cyl .

I changed the plugs, put a can if inj cleaner, still same problem.

I have been driving the car last few days, and it drive fine under light load, it's when i push on the trottle more and when it get under load, then it missfire and i loose most of the power.

Any idea...?

PS. i changed the gas filter and air filter 2 moths ago.

[robert52]

i have the same problem with a 2000 540i v8 and nobody can find yhe problem i think mine is elec

[emiliomax]

Is your check engine light on? Check your distributor cap and rotor. Also, check your wires and coil. One other possibility, the alternator is malfunctioning. Not producing enough juice. Sounds weird, but it was happening to me. Replaced the alternator and the problem was fixed. Worth checking out

[leegardner]

Hi I have a 540 V8 1994. And guess what I got the same problem. Done same changed plugs. But problem still there. Had a Check Control on dash board. Can run fine when parked up night before. It was the next day the problem began !!!!. has any one solved it yet and wy it happened !

[marti5]

Originally Posted by robert52

i have the same problem with a 2000 540i v8 and nobody can find yhe problem i think mine is elec

You are a little different with the V8, have you changed your fuel filter? also the V8 engine sits a a slight chamber, leaning back, check for oil around the spark plugs esp the rear two on both banks, then there's the PCV valve which is bolted to the rear of the engine on the in take manifold ( these do go sometime guaranteed), after that there's the camshaft sensor or crankshaft sensor, then there's the MAF, Well I hope ive given you somewhere to start.