pinging

[BERTO]

hey everyone,i'm new to the board.i have a 91 explorer with 165k.its starting to ping alot now,i have changed the plugs and upgraded the gas to 93 octane.it is less of a ping now but not gettiing better.does any body got any idea on what it could be.

 

[Redrig]

try cleaning the maf. you can also search the site and find lots of info on this.

 

[MrShorty]

Pinging on the 4.0 OHV has many possible causes, and all of them have been discussed before. One cause is carbon build-up in the cylinders. Seafoam or similar cleaner can clean it out. The other cause is from the engine running lean. A dirty MAF can cause the engine to run lean. A vacuum leak or intake leak downstream from the MAF can cause the engine to run lean and ping. One vacuum leak that shows up on this engine is a leak through the lower intake manifold gasket. Many times, the bolts just need to be tightened. Sometimes dirty fuel injectors don't feed enough fuel and cause the engine to run lean.
That's a start. Have fun.