Intermittent rough idle

RALLENBY

MEMBER
2002 BMW 745
4.4L
V8
2WD
AUTOMATIC
150,000 MILES

Hello, my car listed above 745i has a rough idle intermittently. I just rebuilt heads and replaced timing chain guides myself. New AGM fully charged battery. Smoked tested and diagnosed at BMW dealership. Misfire on bank 2 5, 6, 7, and 8.
I used AGM timing tools when I set the cams.

Is it possible that the timing is out on the left side just slightly enough to get misfires, but close enough the eccentric somewhat compensates for it?

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

Camshaft timing is important but it should give a code if there is a problem. There is a ground wire for the coils on each side of the engine can you confirm there is a good connection? Please let me know.

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Saturday, June 29th, 2019 AT 7:33 PM

RALLENBY

MEMBER
2 POSTS

Yes, confirmed all grounds are clean and secured properly. I did a full continuity check on all pins. Voltage check on all connectors 14 volts engine running. Ground continuity on all ground pins.

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Sunday, June 30th, 2019 AT 12:03 PM

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

It sounds like it is lean due to a MAF sensor that needs to be replaced which is common. The hot wire becomes contaminated you can try cleaning it but I have better results with a new sensor. here is a guide to walk you through the steps and diagrams below to show you how on your car:

https://www.2carpros.com/articles/how-to-replace-a-mass-air-flow-sensor-maf

Check out the diagrams (below). Please let us know what happens.

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