Hey fellas i have 93 4.0 v6 explorer and It has what I think is piston slap... I'm not sure exactly but It goes away when you take the plug wire off the #4 cylindar. I was told that you can try using a thicker oil or addative to help reduce the noise... It calls for 5w-30 ... what should I be looking at putting in? Or maybe an addative? It has 200,000 miles on it so I don't want to bother with a new engine, just get rid of the noise. Someone said it might be detanation as well... not sure what that is!

Thanks guys

 

Piston slap in a worn engine can usually be heard as a "thunk" sound directly over the worn cylinder. If you have an engine stethascope or similar listening device, this clearly shows what is happening as compared to other cylinders. Valve train okay? Might want to pull a valvecover and take a good look too, with engine running. What happens is the cylinder is actually slightly larger than the piston, so the piston can move back in forth inside the cylinder. "SLOP" in layman's terms.

Are you burning oil? Do you have any smoke out the tailpipe on start-up? Hazy light blue smoke when fully warmed up? Do you get any smoke haze out of the the tailpipe when accelerating suddenly?

I would go up to a 10w40 oil, a HIGH MILEAGE formula. Valvoline Max-Life and Castrol's Hi Milegae oils are excellent, IMHO.

Then I would move up my OCI's to around 4,000 miles between changes with a fresh oil filter every time.

Nothing completely cures worn engine parts, but this would be helpful. A 1/2 quart of say Lucas Oil Stabilizer would be okay too, but don't overfill with total oil capacity.

 

Might be the timing chain/belt.