Which Spark Plugs?

[White340]

Hi,

I have a 2018 M3 Comp with 27k miles on it fully stock. The plugs were changed at the 3y service by the dealer. I subsequently noticed the idle was a little rough on cold starts (hiccups here and there) but when it got warm it was fine. I never looked into it but before the warranty expired I checked and saw on Bimmerlink that these hiccups were actually misfires. I didn't get a CEL though until 2 weeks before warranty expired.

The dealer as a result replaced two plugs and coils on the cylinders that had the misfire according to BL (usually 20-30 per cylinder during cold start idle). Subsequently, I saw random misfires on other cylinders (usually 5-10). Took it back and they replaced two more plugs and now I get occasionally 1 or 2 but on random cylinders. The car drives fine and no CEL but I still don't like that I get these misfires.

I am going to replace my air intake filters and thought that I might as well replace plugs while I'm there. At least I can properly torque it and see what plugs they used (hoping they used proper plugs and torqued it down).

Before I place my order, I want to know which stock plugs I should use.

FCP Euro has:
BMW RB ZMR5TPP330 High Power Spark Plug - Genuine BMW 12120039634
BMW High Power Spark Plug - Genuine BMW 12120042724

Given the info above, should I be using one over the other?

Also, should I replace all 6 coils while I'm there or is this just a waste of money?

Lastly, anything else I should check that could be causing this? i.e. dirty MAF, air leaks etc.

My driving habit is mostly highway. This is not my primary so usually take it out on nice days and drive it pretty easy.

Thanks

[bagekko]

Real OEM says the part # is 12120039634

I haven't heard of any issues in a long time on BMW coils in general they should last 10-15yrs 100-120k miles.

FYI you will need a long thin wall plug socket to change, the typical ones won't fit/work.

I bought these for future use if needed.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[jaylazy2020]

Yes. Thin wall swivel socket is vital.

I had had taken everything off very methodically only to realise my spark plug socket was just fouling off the kink in tunnel.

A friendly mechanic who near by was able to cut it and re weld it and the shorter length fitted with a swivel ratchet.


If you plan to tune perhaps go with the coder NGK?

I’m stage 2 now and on 99ron fuel it idles smoother than ever.

Also worth upgrading the charge pipes seeing as you’ll have them off

[TopJimmy]

Since you are stock and not tuned the OEM plugs are fine. You will need to gap them down to 0.028”-0.025”. Out of the box they are gapped far too wide.

You could switch to the NGKs, but since you’re chasing a misfire I would not.

Other tips:
-Tighten your plugs to 25Nm, not 23Nm like the box says.
-Use a foot of silicone hose as a “plug threader” to put fresh plugs in the holes and start the threads. Hand threading won’t cross thread a plug.
-When using the hose, place the plug in the hole with the grounding strap at the bottom, so it acts like a scoop and helps the edge of the plug get into the hole. This protects the center electrode iridium coating from getting chipped or scraped.

I use a sharpie pen and mark my plugs and coils with 1..6 dots, so I know which cylinder they belong to. That helps you stay consistent and find problems. Whenever a car runs funny spark plugs were the first things I examine, and very closely.

[GregW / Oregon]

What is the recommended spark plug change schedule (2015 M4)? Dealer says it's mileage AND time based. I don't see how spark plugs wear with time - sounds like BS?

Edit: Dug out my manual and it says every 6 oil changes (6 years) or 60,000 miles. I have 24,000 on mine and dealer was wanting me to change them for $1,200.

[M3orbust]

Originally Posted by GregW / Oregon

What is the recommended spark plug change schedule (2015 M4)? Dealer says it's mileage AND time based. I don't see how spark plugs wear with time - sounds like BS?

I know heard the same thing from my dealer. They did them at 25 k car has 40k on it and past the 3 year interval.
. I did it myself not paying 1200 for 6 plugs to be changed. Like I figured 15k miles those plugs looked just fine I really dont think I needed to change them.
Iam also oem no tune, used the stock bmw m plugs pre gapped from fcp euro no problems been 2k miles since

[gerri]

Originally Posted by GregW / Oregon

What is the recommended spark plug change schedule (2015 M4)? Dealer says it's mileage AND time based. I don't see how spark plugs wear with time - sounds like BS?

In Europe every 2 oil changes or 4 years or 60,000 km. Yes, in Europe the oil change is every 2 years or 30,000 km (absurd). I do about 4,000 km a year, so in 4 years it's 16,000 km and I don't change the spark plugs at this mileage. They do not deteriorate over time...

[Kilabyte]

Originally Posted by gerri

In Europe every 2 oil changes or 4 years or 60,000 km. Yes, in Europe the oil change is every 2 years or 30,000 km (absurd). I do about 4,000 km a year, so in 4 years it's 16,000 km and I don't change the spark plugs at this mileage. They do not deteriorate over time...

I can see the oil being changed based on usage AND time as it can break down, but plugs being changed based on time is just silly.

That said, I've gapped mine 2 weeks ago and they've been laying on my bench waiting to be replaced, maybe today...