99 dodge ram 2500 5.9l gas

[jtoyotaman]

also my truck 99 dodge 5.9l gas, under a load it will ping and detonate really bad even though i use 93 octane. the truck only has 60k miles and has only had regular oil changes and such. one thing about it is that it has sat for long periods before we would use it.any help as to what is causing this do the valves need adjusting,valve seats?

[scoutinkeith]

check the plenum gasket. these gaskets are known to go bad on both the 5.2 and 5.9L engines. the intake manifolds on these engines are two pieces, and the plenum gasket is the gasket that is between the two pieces, when it goes bad, it allows oil to be drawn from the crank case and into the combustion chambers, and will cause pinging under load.

to check the gasket, remove the air hat, manually open the throttle blades, and shine a light through the throttle body(so that you can see the bottom of the intake manifold) if there is oil in there, chances are that the gasket is bad.

if it is bad, you have several options,
1: pay dealership around $400 to replace the gasket (that will more than likely fail again)
2: purchase an aluminum plenum pan from someplace like hughes engines( http://www.hughesengines.com/ about 1/2 way down on the page)
3: purchase a M1 performance intake (they are all one piece, so you never have to worry about the gasket again)
4: purchase a gasket set from your local parts store, and replace the gasket yourself for around $40

[scoutinkeith]

also, if the gasket is ok, there are a few other things that you can try(although, I'd bet the gasket is bad).
you can try running a 180* T-stat, or a cooler heat range spark plug.