soot on Spark plug

[Rodolfo]

Hi Everyone,

I noticed that only one of the 4 spark plugs in my 2004 Elantra, is coming out with a lot of black soot on it,

So I did a regular change, and after a week the new one look really bad.

So I swapped the injectors after reading some other posts, and got new cables.

also swapped the dirty one with one of the clean ones, after another week same issue,

Also tried pulling the boot while the car was running, and the spark sound good and looks ok, the car obvusly starts running rough when I do this

so any other ideas to figure why I get so much soot on that one spark plug

Oh! dont know if it matters but isthe number 4 spark plug the one closest to the driver side in my case.

TNX

Topic

[Mike]

OK, so the only spark plug that always gets sooty is #4–even when you swap in a known good plug from another cylinder?
All the other spark plugs look white?

Is there oil in the spark plug well where the spark plug fits into?
If there is, even though the coil is making a good spark, the spark gets grounded out by the oil, instead of jumping the spark plug gap.

One circuit inside a coil can go bad so that it fires one plug strongly but not the other one.
Another thing you can do is to first clean up the sooty spark plug . Next swap the 2 coils, so that coil 2 3 now fires plugs 4&1 and vice versa.
It’s a pain to get to them, so this video should help…

If a different cylinder now gets the sooty plug–you’ll know you need a replacement coil.

Last of all, you can do a compression test to see if the problem is with the engine itself.

Do an oil change to get rid of all the gas that has been getting into the oil because of the misfiring cylinder.

[Rodolfo]

Hello Tahnkyou for the coil SWAP Idea I will try that tomorrow and let you know

Rodolfo

[Rodolfo]

Hi this weekend I swapped the coils so now the #4 cylinder is sparkking out of the #2 will be using the car this week to see If I can notice anny changes and re-check the plug this saturday.

will let you know what I find

[Author]

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