My 2000 Dodge Durango 5.9 engine feel like it going to install in the morning also the tachometer move up and?

My 2000 Dodge Durango 5.9 engine feel like it going to install in the morning also the tachometer move up and down! But when the engine had been warm in running for a while the tachometer stay still on idler! It got a new air filter and a pcv valve! Any suggest?|||it could be the idle air control valve ?? it could be low on coolant,valve works off of coolant temp.