I have a 1999 dakota sport 4x4 with a 3.9L V6. Recently my check engine light came on with the code P0302 - Misfire Cylinder 2. I replaced the spark plugs with autolites, put new plug wires, distributor cap, and rotor button on it. The light went out for a few days but now if I go out and start up of a morning and let it idle to warm up the check engine light comes on with the same error code P0302. Any suggustions on what could still be causing the misfire in cylinder 2 only since it has new plugs, wires, distributor cap and rotor button? It has 92K miles on it.

Thanks for any help....

 

I would pull the plug in cylinder 2 and see what it looks like. if its oil fouled you have a problem. if its clean then it must be an intermittent ignition glitch. either way it sounds like you're headed for the shop.

 

This may sound too simple, but injectors do get pluged once in a while. Try a bottle of your favorite injector cleaner. It sounds like the last cheep fix you have left.

 

Thanks for the advice. When I changed the plugs, #2 did not appear to be oil fouled. They all were ready to be changed - black with use, but none appeared to have any oil on them. I'll give the injector cleaner a shot and see what that does for it.

Thanks again.

 

you didn't say if it still missed or not, i know you have to use a scan tool to reset error codes in 99 and new rides even after replacing 3 sensors in mine it wouldn't recognize this until a scan tool was used to reset everything. so get 1 from Jegs or Summit for about 200+ or take it to a shop they may just charge for a reset

 

After running a bottle of fuel injector cleaner through it the check engine light did go out, but only for a while. I have since discovered that the only time the check engine light will come on is if I start it up and let it idle for about 20 minutes first thing of a morning. If I simply get in and go, the check engine light never comes on. It is only when I have let it idle to warm up on a cold morning. Even when the light is on, it does not appear to affect the overall driveability of the truck. It still seems to run okay and I can't seem ot detect any type of knocking, missing, or sputtering. I don't know what to try next since it is not a constant on problem with the misfire cylinder 2 error code.

Thanks!

 

I'm having the same problem with my '02 3.9V6. Cyl 3 is giving me the same trouble P0303. Changed plugs, wires, cap, rotor etc, did the fuel injector and Mystery Oil thing. swapped injectors around etc, etc. The compression on all cylinders are 140-145 lbs.

The dealer wants to pull the head and send it to a machineshop to look for cracks. Of course he sez it ISN'T covered under warranty.. Cost would be about $1500 and they don't guarantee they'll fix the problem......... No Thanks.......

From looking at my scanner, it sez I'm may have a problem with an O2 sensor. Seems the sensor (which one, I haven't localized yet) is staying in "closed loop" mode all the time. Its supposed to (correct me if I'm wrong)
be in "open loop" mode when the engine is cold or under WOT (wide open throttle) then go "closed loop".

I can clear the code with my scanner and it lasts for 3-4 days until let it idle cold in the morning to scrape
the windows/remove the snow.....

I have an O2 sensor in the exhaust manifold on the same side as cyl 3, so it could be that one.
Seems the cable from the sensor to the wiring harness is short and has no slack in it, so maybe there is an
intermittant condition due to the tension/vibration on the cable and connector.
When the weather warms up a bit, I'll check it out and report back.

DakotaJoe

 

Just wanted to provide an update. Since using the injector cleaner, I was advised to change the oil and use Penzoil High Mileage this time. I did so and after about 1500 miles on it, the check engine light does not come on, even in the morning when I start it up and let it idle to warm up. Don't completely understand why switching oils could help, but that has been the only thing I have done and it has been as cold as ever here in the mornings. I had already been using a high mileage oil since I have 92,000 miles on it, but Penzoil is "supposed to be" a cleaner oil and the high mileage additives are likewise supposedly good for your engine. Who knows, maybe it was just luck that stopped the check engine light from coming on, but for now it is not lighting up when I let it sit to idle so I am not going to complain and I will keep using Penzoil High Mileage.

 

dakota joe the dealer is screwing you i took my 5.9 R/T in for a window regulator warranty job while i had my supercharger on and they seen it a few months later i ccoked the motor put it back to stock and they warranted both crackrd heads and a few rockers + pushrods

 

Finally got it fixed. Took some time, but the passenger side head was cracked and the valves in all cylinders were a little bit burnt. So for a few hundred bucks I had the cracked head replaced (came with new valves) and the others ground and re-seated. Runs like a champ now.