N54 (E92) Spark Plugs/Coils bad every 6-7k miles

speedbee13

Private
Dec 13, 2021
29
1
5
0
Wake Forest, NC
Ride
2010 BMW 335i e92
Hello all, first forum post so I hope I do this right. Got my car in April this year(2010 BMW 335i e92), and it currently has 70k miles.

Mods:
VRSF Dual Cone Intake
Upgraded Chargepipe
VRSF 7.5" Intercooler
BMS Oil Cooler Valve

Maintenance:
Valve Cover Gasket 65k miles
Oil change when I got the car(62k), 65k miles, and 70k miles
Plugs: 63k miles, second set of plugs in between 65 and 67k(replaced 1 by 1 as they went out), 70k miles(NGK 97968
Coils: 63k miles, second set of coils in between 65 and 67k(replaced 1 by 1 as they went out)
Injectors: Replaced with new(I assume) Index 12 sometime before I bought the car(Leak tested yesterday)

Tune: MHD Stage 1+ 93oct

I replaced plugs and coils so often because of misfires during driving and during cold starts. Right now no issues but it's only been 500 miles or so since plugs were replaced, and only other thing I've noticed is oil temp has dropped to around 190-200* while driving normal since I put the new oil cooler valve in, but that's the point of it. Any idea why my plugs/coils keep fouling out?
 
Solution
Arcing? Not familiar with that. I would do logs but I dont have the log license and can't buy it right now. I bought from fcpeuro and replace all at the same time.
Spark plugs fire at insane voltages, and sometimes the spark can travel thru the coil boot. You'll notice tell tail signs of that on the porcelain part of the plug. Can cause damage to coil or plug. Dielectric grease helps prevent that from happening. People have differing opinions on whether the grease is necessary, but I've always used it. It goes in the coil boot where it meets the porcelain.

wheela

Sergeant
Jun 4, 2021
359
199
0
Twin Cities, MN
Ride
2015 e84 X1 35i Msport
Not sure if this is your issue, but cooler plugs tend to foul, as you need heat to burn off carbon deposits. Perhaps that lower oil temp is having a similar effect? Was there a specific reason you wanted cooler oil temps?
 

corbanistan

Specialist
Jul 26, 2021
91
1
42
0
Florida, USA
Ride
E93 335i 6MT
I don't think that would be the issue, he's reporting failure within a very short span of time. I've also never seen anyone have fouling issues with colder plugs on this engine..
 

wheela

Sergeant
Jun 4, 2021
359
199
0
Twin Cities, MN
Ride
2015 e84 X1 35i Msport
Yeah you're probably right about that. I guess I was more questioning the lower oil temp. I imagine significantly cooler oil flowing through the head would pull more heat out of the plugs, causing them to run even cooler than anticipated. But maybe that's not enough to have a noticeable affect on the condition of the plugs.
 

speedbee13

Private
Dec 13, 2021
29
1
5
0
Wake Forest, NC
Ride
2010 BMW 335i e92
What's your spark plug gap at? How do your logs look? Have you been verifying that misfires are definitely the coils/plugs failing and not something else?
Gap is at .022, haven't been able to log to a file yet but nothing looked mad when monitoring all temps, boost, knock degrees, and timing. I'm pretty sure the misfires are from plugs/coils because when I replace the plug or coil the misfire is on, it goes away. And right mow I can do full throttle pulls no issue. Not sure what else it would be as injectors are fine.
 

speedbee13

Private
Dec 13, 2021
29
1
5
0
Wake Forest, NC
Ride
2010 BMW 335i e92
Not sure if this is your issue, but cooler plugs tend to foul, as you need heat to burn off carbon deposits. Perhaps that lower oil temp is having a similar effect? Was there a specific reason you wanted cooler oil temps?
I put the oil cooler valve on just recently, and the misfires were happening before that. Now that I'm looking at it I could just put the stock valve in and put the better one in when I'm at the track. No real reason to want them lower, I just didn't realize the n54 is made to run as hot as it does.
 

corbanistan

Specialist
Jul 26, 2021
91
1
42
0
Florida, USA
Ride
E93 335i 6MT
I really don't think the oil cooler valve is the issue, I'd leave it to avoid having to reopen the plate for it all the time. I've had mine in for more than a year with 0 issues.
 

corbanistan

Specialist
Jul 26, 2021
91
1
42
0
Florida, USA
Ride
E93 335i 6MT
Are you using any dielectric grease in the coil boot? Tightening plugs to spec with torque wrench? Are the plug holes clean? I usually use brake cleaner and compressed air to blow out dirt and debris before I remove old plugs. Then clean the holes by hand after old plugs are out. Make sure connections to coils are clean.
 

speedbee13

Private
Dec 13, 2021
29
1
5
0
Wake Forest, NC
Ride
2010 BMW 335i e92
Are you using any dielectric grease in the coil boot? Tightening plugs to spec with torque wrench? Are the plug holes clean? I usually use brake cleaner and compressed air to blow out dirt and debris before I remove old plugs. Then clean the holes by hand after old plugs are out. Make sure connections to coils are clean.
I have seen a lot of people using dielectric grease, but I haven't yet. I have not tightened to spec but I got really close(my torque wrench is off by 3lbs, but I can't remember if it's higher or lower so I assume higher so I don't break anything.) I recently walnut blasted my intake valves, and apparently I didn't do it right cause I got shells literally everywhere. Last plugs I put in I cleaned the socket with a shop vac cause they were dirty. Obviously having walnut shells everywhere can cause issues but I made sure to clean them out from anywhere in the engine and I also have had this issue long before I did the blasting. After I did it I actually felt an improvement, but I definitely need to take it to someone to get it done properly, cause I wasn't able to get it as clean as I wanted.
 

corbanistan

Specialist
Jul 26, 2021
91
1
42
0
Florida, USA
Ride
E93 335i 6MT
I guess keep driving until it happens again. Do some pulls here and there. Maybe try to get some logs saved thru MHD. When a coil/plug goes out you should replace all 6. If you order on FCPEuro they give you lifetime warranty. Check for any signs of arcing when you pull plugs too.
 
  • Agree
Reactions: SlowE93

speedbee13

Private
Dec 13, 2021
29
1
5
0
Wake Forest, NC
Ride
2010 BMW 335i e92
I guess keep driving until it happens again. Do some pulls here and there. Maybe try to get some logs saved thru MHD. When a coil/plug goes out you should replace all 6. If you order on FCPEuro they give you lifetime warranty. Check for any signs of arcing when you pull plugs too.
Arcing? Not familiar with that. I would do logs but I dont have the log license and can't buy it right now. I bought from fcpeuro and replace all at the same time.
 

corbanistan

Specialist
Jul 26, 2021
91
1
42
0
Florida, USA
Ride
E93 335i 6MT
Arcing? Not familiar with that. I would do logs but I dont have the log license and can't buy it right now. I bought from fcpeuro and replace all at the same time.
Spark plugs fire at insane voltages, and sometimes the spark can travel thru the coil boot. You'll notice tell tail signs of that on the porcelain part of the plug. Can cause damage to coil or plug. Dielectric grease helps prevent that from happening. People have differing opinions on whether the grease is necessary, but I've always used it. It goes in the coil boot where it meets the porcelain.
 
Solution

speedbee13

Private
Dec 13, 2021
29
1
5
0
Wake Forest, NC
Ride
2010 BMW 335i e92
Spark plugs fire at insane voltages, and sometimes the spark can travel thru the coil boot. You'll notice tell tail signs of that on the porcelain part of the plug. Can cause damage to coil or plug. Dielectric grease helps prevent that from happening. People have differing opinions on whether the grease is necessary, but I've always used it. It goes in the coil boot where it meets the porcelain.
I'll look into that, thanks!
 

speedbee13

Private
Dec 13, 2021
29
1
5
0
Wake Forest, NC
Ride
2010 BMW 335i e92
Spark plugs fire at insane voltages, and sometimes the spark can travel thru the coil boot. You'll notice tell tail signs of that on the porcelain part of the plug. Can cause damage to coil or plug. Dielectric grease helps prevent that from happening. People have differing opinions on whether the grease is necessary, but I've always used it. It goes in the coil boot where it meets the porcelain.
I just looked it up real quick, so having yellow on the ceramic(I assume burnt ceramic) means I likely have arcing?
 

matreyia

Major
Apr 19, 2017
1,767
692
0
Ride
335i e93
1. Put in stock plugs using dielectric grease on ceramic for a few months.

2. If things are good repeat with upgraded plugs. If you aren't using the grease you will see yellow burn marks and that is not good.

3. If things still bad, replace all injectors.

From cheap to expensive.
 

speedbee13

Private
Dec 13, 2021
29
1
5
0
Wake Forest, NC
Ride
2010 BMW 335i e92
1. Put in stock plugs using dielectric grease on ceramic for a few months.

2. If things are good repeat with upgraded plugs. If you aren't using the grease you will see yellow burn marks and that is not good.

3. If things still bad, replace all injectors.

From cheap to expensive.
Injectors are definitely fine, did a leak test this weekend, and they are all new index 12's that got put in sometime before I bought the car. Going to use dielectric grease as soon as i pick some up.