Hey guys, My 2001 V6 mustang cylinder 4 spark plug has been repeatedly getting carbon fouled. I have changed that spark plug twice now in the past month due to it fouling out. Today I noticed car was hesitating/stumbling so I removed the cylinder 4 plug and sure enough it had a ton of carbon on it.…

Try running a slightly hotter spark plug in that cylinder. Understanding Spark Plug Heat Range Depending on the engine modifications you’ve made, you’ll need to take a few extra factors into consideration before settling on the right spark plugs. These factors include spark plug seat des…

I have thought about that and will probably try that next. I just can’t think of WHY only that one plug is getting fouled and not all of them. Is there any other part that I haven’t listed that could be the culprit? I just did the fuel pressure regulator today so only time will tell if that fixed t…

Although it is rarely confined to one cylinder, I wonder if the valve stem seals for that cylinder may be defective.

Run a dry and wet compression test on that cylinder. You may be losing one; or all of them actually and those deposits could be oil instead of gasoline. Just my 2 cents, but a compression test is mandatory with any engine suffering a performance problem, fouled plugs, dead misses, and so on.

Smell the plug to see if it smells like gas or oil.

Wouldn’t low compression in a cylinder almost always throw a code? I don’t have any codes

There is no low compression code. There is no sensor to measure that. You might see a misfire code and it could be intermittent. Leave that plug in a while longer and you are highly likely to see a misfire code set. You can’t rely on the cars computer to tell you everything that is wrong. It isn’t …

If you do a google for fouled plugs, one of the first things that comes up is “if #4 is fouling, check valve guides”. Not that anyone on the internet knows what they are talking about.

You mean everyone but you and me I’m sure.

Only one spark plug is getting carbon fouled?

Maintenance/Repairs

Tester September 8, 2020, 1:45am 2

Try running a slightly hotter spark plug in that cylinder.

Tester

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Only one spark plug is getting carbon fouled?

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