I need help. I have a 1998 Dodge Dakota Sport with the 318 (5.2L) Magnum V8. The first time I tried taking it on the highway after purchasing it second hand, I had big issues with misfiring cylinders, loss of power, and truly terrible efficiency, however it would still idle fine when I pulled it over. Seeing as it had about 190000km on it, I figured it was high time do plugs, wires, distributor cap and rotor. Ever since then, I've had issues with a persistently rough idle and somewhat random misfire. I can't tell which cylinder is missing but the only code that ever comes up related to it is P0306 (cylinder 6 miss). The only other code that comes up at all is downstream 02 sensor (P0138) as I cut out the catalytic converter because it was rattling. At this point I've replaced all the new plugs, tested resistance across all the new wires, listened to the fuel injectors with a screwdriver and tested compression on all 8 cylinders. I'm out of ideas. Does anyone out there have any ideas? Please help!

 

Check the valve springs... Might have a week one.... Just my 2 cents

 

Timing is done by the computer I think so maybe re index the distributor. As Bob said check the valve springs