i just bought a 2001 dodge ram 2500 with the 5.9 v8 auto. its fine when you first start it but drive it a ways and let the rpms drop below 1000 and it starts trying to die and pinging and only after it warms up. even in park it does it. i just need help.

 

I don't know but you might start by checking to see if you have a leaking manifold plenum lower gasket. It is common and your symptoms reflect a possible link.

Take your air cleaner hat off the throttle body. Hold the throttle open, with the engine off, and shine a light down the throat. Do you see metal (good) or pooled oil (bad), especially towards the back?

Oil=likely blown gasket. No oil, continue troubleshooting.

This is a 5 minute procedure everyone with a 5.2 or 5.9 should do.