Hi guys, I have a 2002 3.7 6.0 automatic Ram 1500 p/u had a check engine light come on, diagnosed as the #4 spark plug misfire. Pulled the plug, alot of carbon build up on the on the #4. replaced wires and new plugs, drove one day, check engine light is back on still reading the same code. again #4 was full of carbon build up, flushed out engine with a little deisl fuel to break down sludge, replaced the #4 plug, same thing. also Truck runs with vibration at 55 mph and has a "thunk" sound most noticed in park at idle, dont think its a knock, sounds more like something is hitting, still have check engine light on and still reads #4. any ides?

 

I don't know the ignition set up on your truck. If it has a distributor have you tried to change the cap and rotor? If it's a central coil pack have you checked to see if it produces a spark for the #4 cylinder? The only other things I can think of are maybe a bad valve seat or oil ring on the piston. I'm not really that sure, but I thought I'd try to throw a little something in. You might also want to post this over in the Dakota's section. I think there is a lot of V-6 expertise over there..also more eyes never hurt.