[CrimsonMoonLight72]

2016 340i stock up to 25k flashed stage 1 BM3 at 25k then at 30k put new OEM plugs In ( kept stock gap of .030 ) but did NOT replace coil packs... I’m at 35k now and I’m thinking of doing the new OEM coil packs now.....do I really need them at this point with stage 1?? And if I should do them stick with the $400 genuine bmw ones??

Thx

[5mall5nail5]

IMHO no. You only need coil packs when they go bad.

[auburnf30x]

At 35k miles, I wouldn't even be thinking about coils yet.

My general rule is to swap them out around 100k miles. I may shorten that interval on this car to 75k miles, but I guess I'll just see how it idles around that time.

For replacements, BMW doesn't make them. I don't know whose they use, but it's a third party vendor that BMW gets to slap their stamp on and charge you a premium for it. NGK or Bosch would be a good replacement choice. German Bosch, not Chinese.

[CrimsonMoonLight72]

Originally Posted by 5mall5nail5

IMHO no. You only need coil packs when they go bad.

Originally Posted by auburnf30x

At 35k miles, I wouldn't even be thinking about coils yet.

My general rule is to swap them out around 100k miles. I may shorten that interval on this car to 75k miles, but I guess I'll just see how it idles around that time.

For replacements, BMW doesn't make them. I don't know whose they use, but it's a third party vendor that BMW gets to slap their stamp on and charge you a premium for it. NGK or Bosch would be a good replacement choice. German Bosch, not Chinese.

Yes I figured that.....when they go bad. I guess I would know when they are bad. The idle would probably be absolutely awful. At idle right after start however I do notice an occasional idle stumble but maybe that’s normal for that to occur occasionallY? When I put the new OEM ngk plugs in at the .030 gap I did notice one of the plugs gap was a hair bigger than .030. I put that plug up front where it easily accessible. But I figured there is tolerance + or - with the gaps.....I’m talking a few hundredths

[5mall5nail5]

Originally Posted by CrimsonMoonLight72

Yes I figured that.....when they go bad. I guess I would know when they are bad. The idle would probably be absolutely awful. At idle right after start however I do notice an occasional idle stumble but maybe that’s normal for that to occur occasionallY? When I put the new OEM ngk plugs in at the .030 gap I did notice one of the plugs gap was a hair bigger than .030. I put that plug up front where it easily accessible. But I figured there is tolerance + or - with the gaps.....I’m talking a few hundredths

In my experience when coils fail they start to misfire under load because they have to ignite a mixture that's richer, etc. I've got a ~800+ HP BMW with stock coils if that says anything. I think people replace coils preventatively. Generally, the circuit in the coil either works or doesn't so you'll have load-induced misfires or complete misfires.

[CrimsonMoonLight72]

Originally Posted by 5mall5nail5

In my experience when coils fail they start to misfire under load because they have to ignite a mixture that's richer, etc. I've got a ~800+ HP BMW with stock coils if that says anything. I think people replace coils preventatively. Generally, the circuit in the coil either works or doesn't so you'll have load-induced misfires or complete misfires.

Ok thx....glad I didn’t go and drop 4 bills on something I don’t need at this moment. What do you feel about the gap tolerances?

[5mall5nail5]

Originally Posted by CrimsonMoonLight72

Ok thx....glad I didn’t go and drop 4 bills on something I don’t need at this moment. What do you feel about the gap tolerances?

Same deal, if you're having spark blow out you adjust gap down. Small gap has pros and cons. I'd stay stock gap. Some people actually recommend not gapping iridium plugs because of how fragile the electrodes are. I run 0.022 on my custom turbo setup but it's very different from F30 stuff. I run stock gap and coils everywhere else.