cilinder 6 misfire, reset ecu, it works

[pandaXcore]

Hello dear friends

car model: 2002 BMW e39 sedan M54.
problem: Have problem with cylinder 6, it is misfiring or ecu turns it off. Cylinder misfires occasionally on warm engine especialy on cold. Resetting it with my OBDII when engine is running, it is starts to work again. Have replaced the coils and spark plugs no result problem appears again.

Please help!

[marvinstockman]

I can't tell you what your problem is, but just turning the engine off and back on will allow the cylinder to run, that is until a misfire is sensed again.

[pandaXcore]

Thank you for respond. but i did not understand what you mean with: "turn engine off and turn it on again until engine misfire sense again"?

[R Shaffner]

I'd pull the spark plug and take a look. (Is there oil around the plug while it's still in? Once removed, does the plug look OK, or is it dark from carbon fouling? Or is it wet with oil?)

If the plug looks ok I'd swap that coil with another one, to see if you get a code for a different cylinder. (I understand that you changed the coil, but it's worth testing it while you're replacing the plug.)

[Mike WW]

There's an assortment of possible problems of course, but I too have had a similar problem, although if I drive it off at least at a moderate pace it goes away and doesn't do the fuel shutoff.

https://www.bimmerforums.com/forum/s...-start-P-codes

[marvinstockman]

Turning the car off resets the misfire condition on the car's computer. When you turn car back on, the cylinder that the computer shut down is allowed to run until the computer senses a misfire condition. At this point, the computer will shut the cylinder down again. Now the check engine light will remain on until senses a 'no misfire' condition for a certain amount, that is only known to the computer. You can do this as many times as you want.

[Touring530i]

That is a very similar symptom to when I had an exhaust valve burn in my M54. Except mine wasn't just a slight misfire, it was a full on power-killing miss. I was on my way home, climbing the Siskyou Mountains in the snow at 11:00 PM. Every time the light came on, I would reset it and the car would run slightly better until it came back on.
Checking compression and leakdown on that cylinder might be a good idea.