Hi everyone i was just wondering how often i should replace my spark plug ignition coils. I am aware that i am suppose to replace my spark plugs about every 60,000 miles but i am not finding anything on how often i should replace my coils. I've seen videos that tell me to replace the spark plug boots instead of the coil as a whole itself, but even then i don't know how often to replace the boots. Should i replace them every time i replace the spark plugs? if i can get some advice on this that would be very much appreciated. i have a 2002 330i with about 70,000 miles on it so im trying to take care of this asap. Thank you all in advance.
Replace coils only if they fail. The boots can be visually inspected for tears or oil contamination. Plugs are actually good for 100k with no issues. BMW recommends them at 100k. You can do them early and maybe gain a little MPG but I doubt it.
I did a visual inspection on my E36 coils and they were literally falling apart. The metal was beginning to melt and fuse, and i was experiencing misfire issues.
I ended up replacing plugs, boots, and coils and it set me back quite a bit $$$... Although performance wise the car was running a whole lot better.
When my E36 died and i moved onto an E46, i found out that it still used the same ignition coil part number, so i swapped the coils and noticed no difference in performance, or when turning the ignition... So to that end, i would agree with bmwbob89 -- Replace ignition coils as required.
As far as i'm aware there is no maintenance schedule with the coils. If they work, they work, if they don't work, you'll know straight away.
As for the boots -- They can deteriorate and the rubber lips can crack / split, so i would at least be checking them and possibly replacing them at the same time as your plugs if the rubber doesn't look healthy. You should get a satisfying "pop" when you pull the boot out away from the piston crown. If it's not making a good seal, then replace.
edit: I would also stay away from cheap knock off boots. I was reading up on them a few months ago and found a lot of informaiton about inferior boots that deliver a weaker current versus the OEM boots. Look into it or just buy a set of BREMI / BOSCH boots.
Last edited by Bacender; 03-04-2013 at 08:03 PM.
I suggest replacing the boots anytime you replace the plugs. COILS when they fail. the boot are cheap. BMW actuatly has TSB's out about the boots deteriorating and causing the plugs to crack. since you are a 02 model IMO you have better coils. I just replaced plugs and boots in my 02 with 75k on it.
In 03 BMW went to the pencil type coils and they fail all the time. I don't think the boots are aval seperate on those coils.
Last edited by 02325; 03-04-2013 at 10:19 PM.
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