Ignition Coils part of Preventative Maintenance?

[MTM]

Just curious to see if anyone replaces their ignition coils on a preventative basis...or does everyone tend to wait until they have a fault? Am replacing spark plugs soon (2009 E92 M3 with 65k miles) and want to get a feel for what the experience has been on the forum.

[pbonsalb]

I would not. Have not read of them as a failure item. Would expect them to last 100k minimum.

[///M Ryder]

Originally Posted by MTM

Just curious to see if anyone replaces their ignition coils on a preventative basis...or does everyone tend to wait until they have a fault? Am replacing spark plugs soon (2009 E92 M3 with 65k miles) and want to get a feel for what the experience has been on the forum.

I just replaced all 8 of mine a couple of weeks ago. Last track day car went into limp mode. Codes were multiple misfires but it turned out to be the idle control actuator. With 51k on the car I figured it was about time. These coils are expensive but you won't really know they're bad unless the car is being driven under a heavy load.....ie....track day. After I got home from the track the car ran like new money under daily driving conditions. Also, you can get the plugs from O'Reilly for about $13 each. If you need help with the job holla at me...................Phil

[SenorFunkyPants]

Doesn't seem like a common problem...although one persons UK engine failure was attributed to a failed coil detonating the crap out of that cylinder including the rod bearing.
I would hope though that you would be able to hear and feel if a coil had failed and your engine was pinging.

[///M Ryder]

Originally Posted by SenorFunkyPants

Doesn't seem like a common problem...although one persons UK engine failure was attributed to a failed coil detonating the crap out of that cylinder including the rod bearing.
I would hope though that you would be able to hear and feel if a coil had failed and your engine was pinging.

The problem with these coils is.....once they cool off they won't fail again until they're really hot. And it takes some hard driving to heat them to that point. I've experienced it and have been told this by a BMW shop foreman and the regional tech person..........Phil

[MTM]

Thanks, Gents. Will hold off until I start committing to some track time (darn sailing addiction and tuition payments for my son keep distracting me!).

[Richbot]

Coils, no matter who makes them, do lose some power over time from heat and cycles, and the older they are the less they can hold up to long periods of high load, but it's not likely to cause much of a problem on a street car. IIRC the guys runing these cars in Grand Am weren't replacing coils very often, or at all, it was one of the questions I asked in the pits. I'm replacing mine at 75k but I'm going to keep the used ones as known good spares. I doubt they're appreciably worse than new but I'm going to be doing plugs anyway and it takes no extra time at all to put new ones in (plus I'm likely to break at least one getting them out because I'm a hack). I've no doubt they'd likely all make it for a long time, but I'm one of those guys whose M3 has been so reliable he's having to hunt for things to spend the "M cars need lots of maintenance" budget on...

These cars are pretty good about yelling at you when a coil is starting to go bad, it will throw a cylinder-specific code. The only real driveline "repair" my car has had in 68,000 miles was a #5 coil replaced under the factory warranty. No symptoms, car ran fine, but when it was pulled it had started to swell

Somebody did a study on GM's LS3 coils (popular retrofit) and found they tend to fall off after a certain amount of time in service.

[///M Ryder]

Originally Posted by Richbot

Coils, no matter who makes them, do lose some power over time from heat and cycles, and the older they are the less they can hold up to long periods of high load.......I'm going to keep the used ones as known good spares.

+1.....got the old ones on standby....................Phil

[SenorFunkyPants]

Its the anti knock sensor in the coil that I would be concerned about.