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Hi hope all is well, I was recently driving on the highway I pushed the car a little bit 2012 c350 and got a misfire, I scanned the code when I got home got p0303 so I went ahead and got a set of sparks and a one coil for cylinder 3, after pulling out the old sparks that were in the car for approximately 15k km (Bosch double iridium) the spark plug in the cylinder ended up being the problem the tip of the spark plug was either broken off or burnt off, I put in the new set of oem sparks and replaced the coil for cylinder 3 to be safe. Drove the car for 30 min everything seems to be fine, but I’m worried about the little piece off spark plug that was missing any thoughts about this situation?
Well, depending on how and when it happened, it might have just exited with the exhaust. If it burned away, I would wonder about the condition that caused that. If it broke off, I would wonder the same. If it stayed in the cylinder, over time that could damage the cylinder wall seriously. You could drive it and hope for the best but in my engine building days, anything that big missing that could get into the intake or cylinder was head off to check.
What does the remaining piece of the electrode look like? Is it smooth as if it burned off? Or is is sharp and jagged like it is broken?
Smooth = cautiously optimistic
Jagged = maybe a problem
A close up view of the plug would help to see how it broke, or did it burn away?
Could use a borescope and inspect inside to see if its still in there. Small telescoping magnet to feel around and maybe get it out, if its still in there. Or it blew out the exhaust valve and its now in the catalytic converter.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
How much do exhaust valves open? Enough to let that piece get pass?
I would definitely not run the engine until you know for sure. Steps I would take:
Remove spark plug.
Hand crank the engine to move piston #3 near to the top of the cylinder.
Get a bore scope in the hole and look around. ($90 at Harbor Freight or check Amazon)
If found, try a small pickup magnet or compressed air to retrieve it or blow it out on of the valves. Make sure the valve is max open.
As said, you don't want cylinder damage or valve damage from a tiny piece of metal flying around.
That said, having driven it for 30 minutes probably would have broken something if it was still in there. By the way, that spark plug looks pretty burnt.
Well, depending on how and when it happened, it might have just exited with the exhaust. If it burned away, I would wonder about the condition that caused that. If it broke off, I would wonder the same. If it stayed in the cylinder, over time that could damage the cylinder wall seriously. You could drive it and hope for the best but in my engine building days, anything that big missing that could get into the intake or cylinder was head off to check.
What does the remaining piece of the electrode look like? Is it smooth as if it burned off? Or is is sharp and jagged like it is broken?
Smooth = cautiously optimistic
Jagged = maybe a problem
i personally think it was burned off it felt somewhat smooth to the touch, but then again im wondering how it got broken off or burnt off as the the spark plugs were fairly new.
How much do exhaust valves open? Enough to let that piece get pass?
I would definitely not run the engine until you know for sure. Steps I would take:
Remove spark plug.
Hand crank the engine to move piston #3 near to the top of the cylinder.
Get a bore scope in the hole and look around. ($90 at Harbor Freight or check Amazon)
If found, try a small pickup magnet or compressed air to retrieve it or blow it out on of the valves. Make sure the valve is max open.
As said, you don't want cylinder damage or valve damage from a tiny piece of metal flying around.
That said, having driven it for 30 minutes probably would have broken something if it was still in there. By the way, that spark plug looks pretty burnt.
here’s a link to a video that shows the spark plug more close up, I’m wondering what caused it to get so burnt like that, car is stock although I was pushing the car when the misfire happened, I also looked into the Bosch double iridium plugs and seen a couple others in the same situation as me with the plugs failing. After I installed the new Oem plugs I did drive about 30 km car ran smooth. Update I’ve driven around 100 km or so now and the still car still running fine and smooth. It definitely doesn’t feel like there’s something in the cylinder. Or making any noise or any unusual sound. This my first time seeing a ground electrode be burnt off or broken off. I’m not sure what I should do? I’m afraid if I keep the car and the piece is still in there it will cause a lot of damage long term.
You’re not going to hear anything. If you did, the damage would be catastrophic.
The bore scope suggested by @JettaRed and @TimC300 should be sufficient to verify the cylinder is clear. I didn’t know one could be bought for a price that low and I don’t have one in my shop (not a pro, I do the maintenance on vehicles for my extended family and a few friends). I would add one thing to the inspection. Take the cylinder down to BDC and inspect the cylinder wall for damage. The cylinder walls are very very hard hypereutectic material so if it just bounced around then exited, I would expect none. But if it wedged between the piston and the wall for a few strokes (it’s too big to stay there), there could be some scarring.
Im just a diy-er and never came across this issue before so I did a little searching around. Im coming up with some kind of detonation or preignition in that cylinder, or a loose spark plug that vibrated and broke off. Its pretty violent inside a cylinder. Have you been filling up with the correct octane fuel? Ive also read a loose plug may pull air in causing it to run lean. I watched the video and cant see the break, probably need a magnifying glass to really inspect it. Im just throwing stuff out there.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
I found borescopes on Amazon for around $30 and ordered one to have on hand. Of course, you can spend $200+ if you want. I do think that it would be only piece of mind at this point. The ground strap of a spark plug is pretty soft metal. If the car is running well, any damage that might have been done is too insignificant to worry about. But, if it is easy enough to pull the plug and get a scope in there, I would.
Interesting, I didn't know they were so cheap. I'd want one that can record and snap photos. I noticed some don't have that option. ill go out and snap photos then look through them on the computer to zoom in and see if I notice anything.
02-05-2024, 01:43 PM
