Hello, I have a 1997 dodge ram 3500 v10 gas. Sometimes when I turn it on, the rpm goes up then almost all the way to zero and the flusters back to normal idle. Sometimes it even hits zero and turns off. The same things happens sometimes when I pull up to a stop sign or light. I have recently replaced spark plugs, a ignition coil, pcv valve, fixed a vacuum line, and ran some injector cleaner as well. It seems to happen more when I have the a/c on

 

a/c on means higher engine load. Make sure you don't have any more vacuum leaks, and clean the throttle body really well. Especially where the IAC motor goes. (remove it, clean the hole, and the valve.) Leave the battery disconnected while you are doing that, when you have it all back together, reconnect the battery, turn the ignition to On, (not start) count to ten, without touching anything else, THEN start the truck.