M52 Misfire Issue

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JungleGus
Old Skooler
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Joined: Thu Mar 17, 2005 11:00 pm
Location: London

Thu May 31, 2018 6:16 pm

I'm running a M52 3.3 Alpina on the m52 2.8 management and am having a few issues.

I got her on the dyno and there was a big misfire at 6K RPM...I changed all the plugs and ignitors, so now this has gone away.

After taking her round the track, there is still a slight misfire, typically 6-7K rpm (although there was one around 5-5.5 at one point). There's also a bit of non-smooth running pootling around town or at idle (it's pretty minor, just the occasional stumble in revs).

I've replaced the crank angle sensor a couple of years ago with a new BMW one...is there anything else, or any sort of diagnostic process/tools I can use to help track this down?

Cheers,
Gus
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pianist
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E30 Zone Regular
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Joined: Mon Mar 12, 2012 11:00 pm
Location: Lancashire

Thu May 31, 2018 10:16 pm

Ignitors = Ignition Coils?

Do you know which cylinder is misfiring? If you do try swapping Ignition coils with other one and see if problem shifts to that cylinder if not then it might be faulty wires or just a bad ground to coil or engine itself, sometimes coils get cracks were they bolt to the engine (due to over tightening maybe) and they start losing contact with ground.
Also injector can be playing up but that's a next step.
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