98 Ranger 4.0L engine knock

[Uncle Al]

Bought this V6 used. Dealer said problem was deposits in engine and they kept it to "burn out" the carbon deposits. Problem came back after a few hundred miles. Lo mileage - 70,000. Knock sounds like a diesel at times. Does not get worse under a load and is evident at idle.

Any ideas?

[EVH5150]

Check plugs,wires,dist. cap and rotor. Also could be incorrect timing. Just some ideas.

[Uncle Al]

All that was checked by the dealer before we got to the burnout procedure.