Cylinder misfires (2 & 3) - more likely an ignition coil or spark plug issue?

[libra15]

All 6 ignition coils were replaced 13 months ago. However, a generic brand of coil was used. No issues until now. Only symptom is an intermittent rough idle (and Service Engine Soon light on). I had the code read which indicated cylinder 2 & 3 misfires.

In this case, is it more likely that the ignition coils are faulty or that the spark plugs are to blame? (Unsure when spark plus were replaced, though I think they have been at some point.) What might point to one versus the other?

I don't have the tools to replace the spark plugs, but I can do the ignition coils myself, so I'm hoping the off-brand coils are to blame.

FYI, the car is a 2003 330i with ~90K miles.

[easymoney]

Move the coils to different cylinders and see if the misfire follows. Also check the intake boot for crack/s or have the car smoked checked if you have an access to one.

[MIKYZZ4]

Do as was suggested above, in addition to replacing the PLUGS!

[Raddee]

Change the plugs if you didn't back then. Only use NGK BKR6EQUP plugs! To change the plugs all you need is a spark plug socket, a cheap and worthwhile investment I'd say.

[MarcoZandrini]

The only brands of coils that should be installed in your car are Bosch and Bremi. PEDIOD. Installing generic, aftermarket coils is a recipe for engine performance issues.

[libra15]

Good info here, thanks. The SES light has now mysteriously disappeared, but I'm sure it will be back. I'll swap the coils in the meantime and see if it throws a different code. I probably should have done some research on coil brands instead of assuming they were all the same.

[Dman4249]

Good info here, thanks. The SES light has now mysteriously disappeared, but I'm sure it will be back. I'll swap the coils in the meantime and see if it throws a different code. I probably should have done some research on coil brands instead of assuming they were all the same.

I am dealing with the same issue. Misfire on 2 and 3. Did the issue resolve after coils were switched around?

[libra15]

I am dealing with the same issue. Misfire on 2 and 3. Did the issue resolve after coils were switched around?

That's a weird coincidence! I haven't done it yet. Though, tbh, I'm thinking of getting a couple Bosch coils and putting them in 2 & 3 and hoping it solves it.

I wonder if the generic coils don't do well in colder temps. Last winter (when the coils were replaced) was quite mild, and this issue flared up during a cold spell. A couple of weeks ago was the first time they'd had to do work in the cold. The SES light went away at the same time that it got warmer here.

The spark plugs are NGK and were changed at 60K, so they should still be okay, in theory, anyway.

[All2kool]

Only use NGK BKR6EQUP...

Or Bosch. I've had Bosch 4417's (which are OEM) in for some time now without a single issue. And they're only about $4 each.

[sprocket1200]

if you can afford to replace the coils, then just replace the plugs and get a set of tools. that will be far cheaper and most likely to work....
I'd try staying away from the multi electrode plugs, i've used single electrode for years successfully on multiple e46s. sure, you may have to change them a bit more, but a couple of beer and some tunes, and you are done!