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Discussion Starter #1
Hi guys, trying to diagnose issues with ignition in cylinder 2. M52 B28.

The problem is quite intermittent. About half the time the car runs smoothly, but half the time it's clearly on 5 cylinders (or just very lumpy). It often switches between smooth and lumpy whilst driving, as if someone is literally flicking a switch for a spark plug off and on.

It threw a code for ignition coil cyl 2 so I replaced it and the code hasn't come back, but the problem remains.

Have tried swapping plugs and coils with cylinder 2 and 1, but the problem always remains on cylinder 2 as shown in the INPA screenshot below:

piMCb6i.jpg

In this album, you can see all my analogue INPA values plus three separate videos of the car idling on the roughness screen. They were all taken one after the other, with no changes. Simply turning the car off and on again. This appears to show the cylinder struggling but not quite failing completely (which it did later in the day as evidenced when I unplugged the ignition coil and it made no difference to the running). Interestingly, cylinder 3 also seems to struggle in these videos.

https://imgur.com/gallery/4Clcmec

Also has new OEM crank+cam sensors.

Compression test showed 120 - 135 range, so all seems good.

All I'm thinking it can be is dodgy wiring to the ignition coil, a failing injector (no code though?) or a bad ECU?
 

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Discussion Starter #2
Fixed! It was the ignition coil wiring harness. I replaced the whole unit with a used one from ebay, super easy and cheap!
 
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