Bought a 98 Econoline 150 with the 4.6, it's having a heavy pinging problem under light to moderate throttle when at operating temperature, but when I give it the onions it stops completely and runs great, the previous owner replaced spark plugs, MAF, TPS, EGR, it doesn't ping when cold, only when it gets to operating temperature. Any ideas would be greatly appreciated. It has 186000 Miles.

 

Not the cheapest test, but an easier one and if you have been burning regular grade gasoline, consider installing a tankful of PREMIUM. That should get rid of a lot of built up carbon which may be contributing to pre ignition.