I have a 92 dakota with a 3.9l. Runs great until it gets to operating temp. Once engine is hot, i shut it off. Try to restart it and will crank but wont start. Once started it will run rough at idle and backfire when accelerating. Replaced fuel filter in rail, fuel pressure regulator. Cleaned throttle body and replaced gasket. All plugs, wires and distributor/rotor replaced. Any ideas?