Ive got an 04 durango with the 4.7... Was driving it a couple days ago and the check engone light out of no where started flashing, motor was running rough. Took it home and read th codes and i get P0300, P0420, and P0430... I know what all the codes mean but i can not find the problem. I had a brand new set of coils that i bought a couple month back to put on but never got around to it... so i changed the plugs and installed the new coils... still no luck... took the fuel rails off and noticed a couple injectors werent spraying as good as id like so i bougth a brand new set of injectors from the chrysler dealership. Changed them all no luck, ive got 56 pounds of fuel pressure... all of my cyls have between 139-146 psi... then i thoguht it might have been some bad gas, but i had filled up days ago and it ran fine... so i siphoned out as much gas as i could and refilled the tank with 93 octane and added lucas fuel treatment like i do everytime i fill up... my last oil change was about 7k ago but i use the 10000 mile oil and change the filter every 3000. Any idea what i can look at next... only thing i find wrong is the coolant was about a quart low... other than that no problems to speak of other than my truck is barely running and wont accelerate... any help would be great.

Edit: and every plug is white on the tip... i assume its runnign very lean... check my filter but its a fairly new k&n kon efilter... i did a recharge just in case but no luck.

 

I wonder if the coolant is entering the combustion chamber with a blown gasket,
FF

 

ive already done a compression test and a leak down test on each cyl. Theres no smoke coming from the exhaust. I live in arkansas and this morning its pouring down rain... i left my house at 6 o clock and drove both my kids to school my wife to work, stopped and got breakfast, and stopped by a store, so i drove my truck for a good 2 hours this morning and it never had the problem not once... but when i parked it last night it was running so bad that when i came to a stop on my drive way it killed itself. i have no clue where to even begin looking.

 

http://www.obd-codes.com/p0420

 

i took the truck to a muffler shop and they said the converters are fine... i just had them replaced about 6 months ago... i guess ill go today and buy some new down stream 02's and see what that does... i havent had a problem with the truck in the last 2 days but its pouring rain... i wonder what would cause it to run so good in the rain?

 

i dont really see it being the 02 sensors but ill replace them anyways... the chances of both going out at the exact same time and at the same time getting a random misfire.

 

So, what was the cause / cure?