I was checking my spark plugs and noticed they have a carbon build up despite being changed within the last year and I was curious as to what may have caused that, I recently changed my ICM as it was bad, could the ICM have caused that?

 

you are going to get some build up regardless.... runing the car with a bad ICM could have caused extra build up as well.... mass build up of carbon is a run rich situation, where fuel that isnt burned efficiently and completely settles in the cyl including the plugs....

when ur ICM was bad it was probably the cause... change them and check em again in a few thousand miles

 

Happens on my Cessna 150 when I am running too rich on leaded fuel during idle and taxiing, the answer is to lean it out and run the revs up on my runup.

Can't really do that in the car though, I would make sure that the engine is breathing good, and just curious, you like at a high altitude? If so, you could try leaning out the ECU or using a ram air?

Good Luck

 

I'll change them and see, I was just wondering why they had so much carbon build up when they never did before, but probably the bad ICM as stated.

 

Hi,
I am the tech manager at Autolite spark plugs. Are you sure you have the correct spark plug heat range? If it is one or two steps cold, you could get substantial build up as the plug tip would not get hot enough to burn off deposits. Certain fuel additives can cause build up as well.