Fouled Plug Cause

F134. Started running rough last time I was out. Found #2 plug had melted. Any ideas for cause? Plugs were new last year.

Recently had motor apart to hone cylinders and replace seals.

#3

#2

#2

 

Can you post picture of the spark plugs ?

 

Better? First two from #2 cylinder. Last is from #3 cylinder.

 

On #2 I can't tell if that's carbon build up on the electrode or metal transfer.
Looks like oil/carbon fouling to me.
#3 looks normal burn, but gap appears too wide to my eye.
Were the plug gaps proper on installation ? .030 if I recall ?

How many miles on these plugs ?

 

What motor oil are you using ?

 

10-40

Probably less than 1000 miles on plugs.

Plugs looked good before last drive. Started acting up after 10 miles.

 

So just hone and old pistons and rings ?

 

Yes

 

Well, I could say a lot, but I won't.
There are a lot of could be this or could be that here....
Process of elimination.
I'd start with a wet/dry compression test, followed by a leakage test on all cylinders.
If those are acceptable/within limits, then check for good spark.
I'd then check to make sure fuel pump diaphragm isn't leaking raw gas into the engine oil, thinning it out.
You could smell this in the oil on the dipstick.
If okay, then just try straight 30 weight oil for giggles.
Other than that, you could have blow by from the piston rings/cylinder wall conditions.

You could have bad cylinder, valve guide or it could be this or could be that......

Don't fret, others a lot better than me will chime in....

 

I will test compression. Thanks.

 

How old are those plugs? That's a lot of rust for plugs with only 1,000 miles. Has the engine been exposed to a lot of moisture?

 

Some good info here.

Know Your Engine - Read Your Spark Plugs

 

That plug being burned out is incredible. Is your ignition timing correct?

 

Plugs were new last year. The Jeep does sit outside under a cover.

 

Not sure. There's no markings to check. I have had to keep turning it down from where PO had it.

 

I have only had the Jeep for a little over a year. It runs good but seems very low on power. Over the winter I pulled the motor just to clean it up and replace some leaking seals. While it was out I saw the cylinder walls looked like glass. A quick hone and put it back together.

This is my first time into a motor. Any advice is greatly appreciated.

Also while looking stuff up, I found that there are resistor and non resistor spark plugs. These are resistor type.

 

Any rational diagnosis cannot start until a tune up to FSM specs. Points, Timing, plug gap, etc.