Nissan Repair: spark plugs, piston rings, nissan pulsar

Question
My 89 nissan pulsar wouldnt kick over, i checked the spark plugs and they were black, looked like oil, so i replaced the spark plugs which fixed the problem, 2 weeks later the car wouldnt kick over and the plugs are black again. The car hasnt had this problem before.Is something in the motor stuffed or do i just need a good tune-up? cheers!

Answer
Corey,  

If it is oil on the plugs, then your piston rings are bad.
When the plugs are wet they are not allowed to spark which is what egnites it.

You will have to put new piston rings in if they are wet.

If its just carbon (exhaust) you will have to do a valve job on your exhaust vavles.

Darrel