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      03-02-2020, 08:06 PM   #1
hC1001
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Just changed the spark plugs. I see carbon buildup.

Changed out the plugs yesterday on my new to me 113K mile 2016 M3. All the plugs were super tight and i was cringing how much force and resistance i was getting when loosening them. Super nervous that i was gonna take out threads of aluminum. I was also freaked out on the first plug because the spark plug well is curved and when you have a socket on it, it looked like someone cross threaded the plug.

Everything came out fine but noticed rust powder after removing the plugs. I used a vacuum with a tube on the end to suck the powder out before installing the new plugs. All the plugs removed were normal. I also checked each hole with a flashlight and i believe i have a lot of carbon buildup It looks like burned cheese in a frying pan. Do i have to worry about this or is the main concern buildup on the valves?

Its an aluminum head right? Where did the rust come from?



Last edited by hC1001; 03-02-2020 at 08:23 PM..
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      03-03-2020, 08:00 AM   #2
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The rust should be a remnant of the plugs. Steel plug threads and an aluminum head mean some electrons are going to migrate if even the slightest bit of moisture gets in there. As for carbon buildup, unless you have a borescope, getting an accurate evaluation can’t be done through the plug holes. The valves will get carbon on them, but the primary concern involves the intake ports. At least one other thread on this forum has shown the S55 to not be susceptible to CBU.
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      03-03-2020, 09:46 AM   #3
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Thanks for the analysis.
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      03-03-2020, 03:44 PM   #4
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any octane boost additives used?
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      03-03-2020, 08:01 PM   #5
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I also noticed some rust when taking out my spark plugs. Also it took quite some force to remove as well. It seems like the dealers really tighten it down and not within torque specs. Glad that I did it myself and now I know its torqued properly.
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      03-24-2020, 06:11 PM   #6
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FWIW...here are mine. Pulled last week. 30,000 miles on them. No boost, gapped stock @ .028.
I did notice a lot of rusty powder on the threads. The tubes looked clean.

Great idea on the vacuuming . I recommend it 1) after the coil is pulled off, and 2) after the plug is pulled out. Basically eliminates the chance for anything to fall down in there during the process.
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      03-24-2020, 11:27 PM   #7
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Thanks for the pic. Looks like they were due for a change sooner or later.
I just took a pic of mine and they look worse than your plugs. There seems to be some buildup on one side of all my plugs too. My car was sitting for a while before i bought it and it took another month after i bought it for the transport to deliver it. I guess the car didnt get to operating temps causing moisture to build and form rust on the threads(speculating). The car feels the same after the plugs were changed but i gapped the new plugs to .023. I wonder how long these plugs havent been changed... I've pretty much done all the necessary and preventative maintenance on the car except a brake fluid bleed and the diff bushings(rear bushing is currently torn). Cant wait to take it to the track when everything is completed and do some HPDEs.

Last edited by hC1001; 03-24-2020 at 11:42 PM..
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      03-24-2020, 11:34 PM   #8
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Are you guys replacing with OEM plugs or NGK?
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      03-24-2020, 11:41 PM   #9
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Quote:
Originally Posted by rborane View Post
Are you guys replacing with OEM plugs or NGK?
I did Bosch OEM plugs. I was planning to keep it stock but i got bootmod3 for it and plan to run CS+ or stage 1 93oct. If had known, i would've probably went with NGK and 1 step colder
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      03-25-2020, 04:00 AM   #10
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Quote:
Originally Posted by hC1001 View Post
Quote:
Originally Posted by rborane View Post
Are you guys replacing with OEM plugs or NGK?
I did Bosch OEM plugs. I was planning to keep it stock but i got bootmod3 for it and plan to run CS+ or stage 1 93oct. If had known, i would've probably went with NGK and 1 step colder
Bosch OEM here. FCP Euro, and no tune for now. My car is an ultra long distance commuter.
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      03-25-2020, 10:06 AM   #11
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Quote:
Originally Posted by hC1001 View Post
Changed out the plugs yesterday on my new to me 113K mile 2016 M3.
Wow, that's got to be one of the highest mileage F80s here. Just curious, what do you know about the service history on this car? I sincerely hope mine gets to 113k with normal maintenance as this is the first car I've even owned where I wasn't bored after 2 years with it.

Those plugs look pretty decent (clean electrode, tannish color) -- any idea how many miles on them? Also, any idea what the semi-circular black mark is -- the one that starts on the insulator and aligns with the black mark on the base of the housing?
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      03-25-2020, 10:57 AM   #12
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Quote:
Originally Posted by RRedline View Post
Wow, that's got to be one of the highest mileage F80s here. Just curious, what do you know about the service history on this car? I sincerely hope mine gets to 113k with normal maintenance as this is the first car I've even owned where I wasn't bored after 2 years with it.

Those plugs look pretty decent (clean electrode, tannish color) -- any idea how many miles on them? Also, any idea what the semi-circular black mark is -- the one that starts on the insulator and aligns with the black mark on the base of the housing?
Yea the plug condition doesnt look bad in terms in colour and condition. I honestly dont know much about the service history. This car looks like it was a long distance commuter car(30k+ miles per year). When doing the maintenance, all the removed parts were BMW branded and not in bad shape. The suspension was still nice and firm. I was expecting a worn out car but it thankfully isnt.

Not sure what the black buildup on the sides of the spark plugs are. Maybe carbon buildup? Im curious to see what the new spark plugs look like when i remove them in the future. I installed an oil catch can and during installation, there was some oil inside the PCV hose going to the intake. Curious to see what the oil catch can picks up too.

Last edited by hC1001; 03-25-2020 at 11:03 AM..
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      04-18-2020, 03:53 AM   #13
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A black, feathery carbon deposit on your spark plugs can be an indication of a weak spark or an overly rich fuel mixture. Causes may include a stuck choke, misadjusted or heavy carburetor float, a leaky injector or carburetor needle valve, low coil output or high resistance in your spark plug wires.
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      04-18-2020, 06:31 AM   #14
hC1001
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Quote:
Originally Posted by advrider6510 View Post
A black, feathery carbon deposit on your spark plugs can be an indication of a weak spark or an overly rich fuel mixture. Causes may include a stuck choke, misadjusted or heavy carburetor float, a leaky injector or carburetor needle valve, low coil output or high resistance in your spark plug wires.
Hi, thanks for the response. I actually looked into this more and the concern with deposits on the insulator are normal. https://www.championautoparts.com/Te...-Problems.html
It does look like i have slight carbon fouling and im going to see how the plugs look when i put 5 or 10k miles on them. Perhaps the ignition coils are getting weaker. I dont really see anything too concerning with the plugs i pulled out.
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