Engine Misfire (Bad Coil?)

[SonnyZ4]

2003 3.0i

Engine ran super rough with almost no power this morning. Code reader showed P0301. I've been doing some research on how to test the coils and what I'm lacking is what the reading on the coil harness/plug should be.

These threads ( http://forums.bimmerforums.com/forum/showthread.php?1345252-e36-How-to-test-coil-packs-(w-pics) ) and ( http://n54tech.com/forums/showthread.php?t=9551 ) give some info on testing the coil packs. I'm not well versed in BMW engines and chassis numbers, so I don't know if I can apply all of this data to mine.

Does anyone know what the reading should be for the Z? If I manage to find the bad coil, do I need to go ahead and replace the associated spark plug?

Also, I read that I could swap coil packs with other ones to see which is bad. Which ones can be swapped with each other?

thanks for all the help!!

 

[Angie4m]

Not sure re what it should be reading but yes you should replace the spark plug and you can generally see from the spark plug which coil has gone. I've always found the spark on a failed coil is very black in comparison to the rest. Yes you can give it a scrub up with a wire brush but considering what a spark plug costs I'd replace it.

 

[MHZ4C]

I'm pretty sure the code indicates the coil, or at least the cylinder if the coil plug isn't at fault. There is a rule to the code numbers and the cylinder number from the front of the car reading backwards (I think...). For example P0301 indicates cylinder 1 misfire. Swap coil pack on cylinders 1and 2 (by completely disconnecting wires and reconnecting after the swap to keep the firing order) and see if the code moves, P0302.

I'm not sure of the exact details but I read a post about this for diagnostics. Worth a search to confirm.

I'd replace the sparks too if it's been a while. I think bad plugs can cause the coils to fail, as they get tired from overcharging the spark plug to compensate for poor performance of the spark plug, so a new coil may suffer without a new spark plug.

Hope you get it sorted!