[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!

[DJtoad]

How are they diagnosing the bad coils? There's really no good test that I'm aware of other than moving a suspected bad coil to a different cylinder and seeing if the misfire follows it. Coil failures really aren't all that common so my guess is that you're not addressing the root cause of the problem and are either replacing perfectly good coils or something else in the electrical system is killing your coils. That issue may have been the result of pressure washing the engine. What codes is your car generating? BTW, carbon build-up on the intake valves has nothing to do with your problem. If your indy suggested that it may be, it's time to find a different indy.

[LovinMyE93]

Originally Posted by DJtoad

How are they diagnosing the bad coils? There's really no good test that I'm aware of other than moving a suspected bad coil to a different cylinder and seeing if the misfire follows it. Coil failures really aren't all that common so my guess is that you're not addressing the root cause of the problem and are either replacing perfectly good coils or something else in the electrical system is killing your coils. That issue may have been the result of pressure washing the engine. What codes is your car generating? BTW, carbon build-up on the intake valves has nothing to do with your problem. If your indy suggested that it may be, it's time to find a different indy.

In all honesty I couldn't begin to say how they're diagnosing the coil issue. Or what codes might be coming up.

As I said, I'm new to the BMW world so I'm trying to learn best I can through these forums.
That's where the carbon question came up, not from the garage.

[DJtoad]

Most shops provide a summary of the problem, including the codes they pulled, along with what they did to address them in the paperwork. Check your paperwork to see if they included the codes, and if they didn't, ask your indy for a list of the BMW-specific codes they pulled. Without the codes, you are shooting in the dark. Generic OBD-II "P" codes are often insufficient to track down hard-to-diagnose issues. You really need the extended set of BMW-specific codes so if your indy doesn't have a means to pull them, you need to find a new indy who specializes in BMWs and/or has the proper diagnostic tools.

[Socket]

Carbon build up should not cause coil failures.... rough idle yes but coil failures no

[KeepRidingDirty]

Originally Posted by Socket

Carbon build up should not cause coil failures.... rough idle yes but coil failures no

+1

As far as I'm aware there is no trouble code for a coil, it's just a standard misfire code (it's highly unlikely your misfire is caused by carbon buildup), typical items to replace are spark plugs>coils(you've already done)>injectors. Your carbon buildup would have to be really really bad to cause misfires.

[AM330i]

Most likely your coils are failing do to worn out spark plugs. I would replace all the plugs, if they havn't already been replaced, and see if that helps.

[LovinMyE93]

All very helpful info, thanks folks. I'll hit up my garage and ask about if they swapped the plugs.