Bad Ignition Coils....how to diagnose?

[Tanks95]

What are the signs and or symptoms of an ignition coil going bad?

[atdM3]

On p. 120-5 in Bentley's is the procedure.
When you look at the coil connector lace your ohm meter between the first and third pins.
you should get 0.4-0.8 ohms
I went thru this recently, misfires. I thought it was the coils I ended up replacing the rubber boots attached to each coil. These were badly cracked at the spark plug connector. The coils were fine. Check your rubber boots.

[Cup of Coupe]

My friend had this problem on his M. It would mis-fire very badly only in 5th and 4th gear and when it was all the way open. It cost him 500 to diagnose at BMW, they had to get the senior mechanic in to diagnosis because it wasn't throwing any codes (this was after he tried everything else).

His case might have had rare symptoms, but hope it helps.

[M3Rob95]

Mine just went bad and I swapped them.

I have two extra sets if you need some to swap out..

I replaced my fuel filter, plugs, o2 sensors, and more trying to fix my problem before I finally bought coils..

The car feels like an M car again

Pm me if you want my extra coils,

Rob

[M3Rob95]

My friend had this problem on his M. It would mis-fire very badly only in 5th and 4th gear and when it was all the way open. It cost him 500 to diagnose at BMW, they had to get the senior mechanic in to diagnosis because it wasn't throwing any codes (this was after he tried everything else).

His case might have had rare symptoms, but hope it helps.

Mine was this "rare" symptom..

No codes here

[JClark]

Like you said, they often dont throw codes. Noticeable loss of power, and usually gets worse as the rpms go higher.

See if you can get another set of coils and swap them out.

[Tanks95]

Looking for a set of Bosch coils as we speak

[///M3///M5]

I have personally NEVER seen a set of coils go bad. The coil boots are a wear item though, and should be replaced every so often.

[MarkR540]

coil failed on me but threw a misfire code. i swapped the coils from cylinder and the code showed up on the cylinder i swapped with.

the car will run like shit basically. big hesitation and virtually no power.

[///M3///M5]

coil failed on me but threw a misfire code. i swapped the coils from cylinder and the code showed up on the cylinder i swapped with.

the car will run like shit basically. big hesitation and virtually no power.

I assume it idled like crap too, huh?

Sure it was the coil and not just the boot?

I have seen single coils fail, but only like 2-3 times, ever.

[Tanks95]

Any issues with the Bavauto "performance" coils?

[MarkR540]

i inspected the boot and it looked like it was brand new. i dont know how big those cracks are supposed to be.