[LovinMyE93]

I've had three ignition coils fail after a misfire (at different times, not all at once) and my gut is telling me this could be the root cause...
I've read some on the forums about the N54 carbon problems, being new to the car and the whole 'walnut blasting' concept, I'm asking for a bit of help...

'08 E93 convertible with 57K mi., purchased in May, and the dealership I purchased from had a clueless detailer- pressure washed the engine compartment during the sale prep.

That caused a couple of bad problems: ABS error that took two tries to clear properly, followed days later by three ignition coils crapping out at once.

They swapped all six at once back in May, and since then we've gone through three more - always crapping out when the auto downshifted.

I'm starting to think this carbon buildup could be the ultimate cause of my IC probs, but I've also read that the Bosch OEM coils have had bad batches too.

Befor I initiate a service expense of this scale, I'd love some input from you guys to see if there's another even more expensive service I've gotta have done.

What other tips could anyone provide on what necessary maintenance that should be done (that might not have been) and what issues should I ask my indie garage to look into?

Thanks!

[WilliamS]

A walnut blasting isn't going to harm anything and can eliminate a few issues these cars have, mostly rough idle, and some misfires but this is usually not the root of the cause for misfires. A misfire is almost 99% not because of the valves being dirty has more to do with either and old plug, a bad coil, or a bad injector. There is a bit more that can go into it but I would start with the coils and plugs. The plugs need to be changed more often than what BMW would recommend if there has ever been a piggy back or a tune on it.

I would chase the misfire, if you are misfiring on the car in stock form you have an issues that needs to be addressed. If you have already replaced the coils and the misfires are still showing up on the same cylinders I would go next to plugs. If you havent changed the coils yet, move them to another cylinder that has no issues. If they show up on the old cylinders you have ruled out the coils, if the misfire moves to a cylinder that was not causing issues before you determined its the coils. Again this is 100% but its pretty darn close.

My car would get a misfire under load with a tune. My plugs were the culprit. While my mechanic was in there (lillyautomotive) I had the valves cleaned. The valves were not as bad as many on here. It was the plugs.

[LovinMyE93]

Thanks for this info, I'll chat with my mech and see what's old and what's new, and see if they've kept notes on which coils have been replaced.