Ok I got a code for the # 7 misfire (P0307) I just wanted see what all I needed to do to fix this. It is 2002 QC 5.9 with 89000 I just bought It about 3 weeks ago so I dont know how long it has been since things have been changed. Do I just need to change the plugs and wires or is there more. What are the best plugs and wires for our trucks or which ones should I stay away from. Thanks grassman

 

if it was me...i'd just go ahead and change everything ie...(plugs, plug wires, cap, rotor) just be on the safe side......then go on from there and see if the misfire is still there, but can't go wrong with changing that stuff anyways since you don't know how well kept the truck was

 

would be best to change them both. Odds are they are original. If the wires are bad, it will miss fire more once it is warmed up too. I would just do the tune up, should help. Is either bad wire or plugs are real bad. Good luck m8

 

Did you buy it with any engine mods? It probably is a plug or wire, but if the cam was ever upgraded, a misfire code is common, and something some people just have to live with. No harm, just a stupid CEL on the dash...
Just something to check if all the obvious stuffchecks outOK...

 

The only mods that I know of was the exhaust. and a 2 inch body lift. Would this code cause my gas mileage to suck.

 

Replace the plugs, all of them. Make sure to gap them correctly. After that do the wires.

I was getting a misfire on my SRT, it was the plug.

 

I hope that it is something simple instead
but the 5.9 V8 have a problem with
cylinder heads cracking between the intake and exhaust seats
especially on cylinder 7 (or 8)

Coolant leaking into that cylinder would cause missfires.

It might pay to carefully examine the sparkplug nose in cyl 7 for white or yellow deposits and do compression tests. Even better would be a cylinder leakdown test with a pair of pressure gauges...with this test you can watch for air bubbles in the coolant and listen with for leakage.

http://www.area51groupllc.com/produc...products_id/30

There is also a chemical test you can buy at NAPA auto parts stores that tests your coolant for the pressence of combustion gases, which would be the tell-tale of a cylinder head crack.

Good luck.

 

If you are popping a misfire code AND your gas mileage is really bad, it sounds to me like that truck is way overdue for a full tune up!!!

 

If you have change all tune up parts the only thing left is the cylinder head. This has been problem with all dodge 3.9 5.2 and 5.9 engines, with high mileage.

 

A mechanic at work told me to just try some injector cleaner and see if that helps first but I think I am going to do a full tune up since I just bought this truck a couple of weeks ago and do not know when the last time everything was changed. Does anyone suggest a certain plug