Fouled sparkplugs

[NY Scotsman]

I replaced my sparkplugs this afternoon as my 2011 328xi has 63,000 miles and has had a rough idle for the last month.

I was pretty surprised to find that cylinders 1 and 6 had fouled plugs (see pics). The others weren't fouled but had good carbon deposits and were degraded. By the look of them they should have been replaced at least 10,000 miles ago or earlier.

Weird things is that beyond the rough idle, the car was performing well. I'd think it would have been throwing codes and having performance degradation....

So, my observation is that the BMW recommendation of plug changes at 100k may be too long for many.

Also, what can I do differently to avoid this carbon buildup? (Note that I drive highway speeds everyday)

Also with that much buildup in plus 1 and 6 should I be concerned about those cylinders?

Thanks.

[asiemers]

Sea foam has worked great for me with removing carbon build up, as well as fuel system cleaner. Driving the car hard every once in a while helps burn off carbon too.

[cochise325]

No pics?

[NY Scotsman]

Here are the pics. You can see the carbon deposits completely bridged the gap in cylinders 1 and 6. 546175546176546177

[cochise325]

After seeing the pics, something is definitely wrong with those two cylinders.

I change my plugs at 50k mile intervals and they have no carbon buildup on them.

Are these the original plugs that came with your car?

Was there any oil in the spark plug wells?

[NY Scotsman]

No oil in the wells or on the plugs. Just plenty of carbon.
These are the original plugs but at 63k miles they should not be this bad.
I did have misfires at around 45k miles and the dealer replaced all coils. Then had a pretty good misfire event on the highway at 49k miles w a nice puff of black smoke (was like an old time misfire). Took it back in and the dealer said they checked plugs and scoped cylinder and everything was fine.
So, if the dealer is to be believed this buildup occurred between 49 and 63k miles from regular driving.
Thoughts?

[cochise325]

Are you throwing any fault codes?

[NY Scotsman]

None on BMWhat and dealer reported none on last visit (2 months ago).

[cochise325]

Amazing that you would get a visible black smoke backfire and not have codes. Have you tried running some fuel system treatment through it? I like the Chevron Techron. If the injectors are dirty, it will clear them up. And it will clean up some deposits on the back side of the intake valves. It is worth running two full tanks of fuel through it, then do an oil change.

Beyond that, I would want to verify that the O2 sensors are good, and the MAF sensor is good. As these parts will affect the fuel-air mixture. But it seems like you would get codes if something was off here.

Are you able to buy fuel that contains no ethanol?

[NY Scotsman]

I was amazed too when they told me there were no codes. Nothing worse than a one off failure that leaves no trace. Makes me concerned that I have a hidden issue lurking in the engine compartment! However it was 14000 miles ago.

Will try the techron. I have been buying gas pretty regularly at a no brand station. Hopefully it is as simple as going back to buying at Chevron and Shell.

You recommend changing oil soon after doing a techron application. This is not listed on the techron application procedure. Why do you recommend an oil change?

(I just changed the oil this weekend)

Thanks for the input!

[cochise325]

I was amazed too when they told me there were no codes. Nothing worse than a one off failure that leaves no trace. Makes me concerned that I have a hidden issue lurking in the engine compartment! However it was 14000 miles ago.

Will try the techron. I have been buying gas pretty regularly at a no brand station. Hopefully it is as simple as going back to buying at Chevron and Shell.

You recommend changing oil soon after doing a techron application. This is not listed on the techron application procedure. Why do you recommend an oil change?

(I just changed the oil this weekend)

Thanks for the input!

Generally, the best time to run the Techron through the fuel system, is just before you do the oil change. But given what you are experiencing, I would go ahead and use it. Costco had a mulit pack of Techron for a decent price.

[NY Scotsman]

Will do. Heading to Walmart tonight.
Idle is super smooth now. Back to the way it was!