4.0L Rough idle/misfire(?) when engine is warm...
I have a 2004 Grand Cherokee with a 4.0L engine and 99k on the clock. The check engine light has come on and I get an intermittent rough idle (500-600rpm) and misfiring/poor performance at highway speeds and when I put a load on the engine (going up a steep grade, ect..) This seems to happen when the engine is at operating temp (~180-200F). Sometimes the engine light will flash when the engine is running poorly. I have put new plugs and a new coil pack in and my mechanic tracked down 3 vacuum leaks, but the problem still persists. The kicker is, engine runs fine before it gets to operating temp. I really don't want to go the dealership route, as the $100 per hour labor rate is hard on my limited income.