My wife has a 1996 Toyota RAV4 with 152,000 miles and the check engine light came on. The first thing that came to mind due to rough idling, etc was the spark plugs / wires. Anyhow, the plugs had never been changed due to it being a PITA but I finally got it done and the problem is solved.

But my question is, when I removed one of the spark plugs, the outside of one of the plugs was well saturated with oil although the dielectric, diode, etc were in quite decent shape, especially for the age of the plugs. Might have just been running a tad lean but that's it.

What can the oil on the outside of the plug be a sign of? The plugs sit on-top of the engine and the only thing that comes to mind is possibly a bad valve cover gasket?

Thoughts?

 

sounds like the valve cover and or spark plug gaskets are worn out. you should pull the vc, clean the spark plugs and replace. should fix it

 

There are a type of press-fit donut gasket around the spark plug tube in the valve cover itself. If one of these develops a leak the oil can get into the tube but can't get out.

Best change out the actual valve cover gasket too when you do the job.

 

This thread has been posted a year go and i just want to state my apology for that...Im on the same boat a week ago and experiencing the same thing...in the morning i noticed that the gas and the clutch are well working but after few kilometers of driving, i would feel it's lack of power...im thinking of replacing the spark plug with a tuned one...would it be advisable? Just curious about it....



Toyota parts

 

You should change the timing belt if you haven't already. It would smooth out the idle and drive smoother.