#2 Spark plug is black all others are fine. Is it the rings or valve stem seals?

[Brown87Rolla]

I was going to do a compresion check but after I get a reading across the cylinders how do I know if it is the Valve stem seals or Piston rings that are leaking? It is only the #2 plug that gets black every two weeks, all others are normal color ( brownish tan ). When I start the car in the mornings it definetly blows blue exhaust.

[reym]

Oh my goodness, if the compression is normal then you are looking at a valve guide leak. Try using a STOP or STP oil additive and replace your plugs with a hotter one, that migh temporarily solve your problem.

[Nick]

check the resistance in that wire and consider getting a hotter plug, if you're getting weak spark it'll look like ou're running rich

[schn0354]

If you get good compression, it is most likely a valve stem seal leak. However, your oil control rings can be worn causing oil consumption while still getting good compression. This was true in my case. I just replaced valve seals and rings, but the wear on my engine was even across each cylinder. In your case, you may have a cracked valve stem seal for just cylinder 2. Do you hear any odd valve train noise? I would only install recommended plugs.

Originally Posted by Brown87Rolla

I was going to do a compresion check but after I get a reading across the cylinders how do I know if it is the Valve stem seals or Piston rings that are leaking? It is only the #2 plug that gets black every two weeks, all others are normal color ( brownish tan ). When I start the car in the mornings it definetly blows blue exhaust.