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2003 Dodge Ram 1500

 

Question: code p0300 muti misfire

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NASCAR, 5.7L V8 HEMI, Egg Harbor Township, NJ, October 28, 2009, 18:57
 Rookie

i keep getting this code p0300. i have 125k on the truck i changed plugs and wires first.then i got a code p0305 i drove the truck for about an hour then the code was back to p0300. i switched coil number 5 an put it to 1 an coil number 8 an pit it to # 2 reset the pcm an tried again to days later the same thing happened again. so then while the engine was running i unpluged the fuel injecters one at a time to see if i could here any diferrance an i did on the # 5 cylinder so i put in a new one and the same thing happened. so i had a mech freind look at it he told me it was probobly intake gaskets ( o rings )so i changed them and i still have the same problem. could somebody tell me if the pcm could cause this problem or maybe the softwere in it could be screwed up. im just not sure how to check it. or how much does it cost to reprogram it.or should i just buy a supertuner and do it that way. can somebody PLEASE HELP!

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  • Answer #1

    Bret Bodas from RepairPal Test Shop, October 28, 2009, 20:54
     Master

    Have you read this yet? It has tons of very good info about the p0300 code.
    My initial thought is that there is a fuel mixture issue, either from a vacuum leak in the intake system or a low fuel delivery issue. What you don't mention is how the engine is actually running, is it misfiring or idling rough? Have you checked the ignition timing?

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    NASCAR, October 29, 2009, 13:53
     Rookie

    The truck idles rough and you can here the mis. its diffrent everyday. one day its like one cylinder missing an anouther day its like 3 or 4 cylinders are missing. thats why i thought it might be the pcm. i forgot to say when i replaced the injector it still idled a little rough but when i drove it it ran better then it ever did for about 3 to 4 hours. i turned it off for the night an started it the next day and it was back to the same thing.im just baffled

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    Visitor, March 11, 2011, 04:39

    i have the same prob wth do we do i put new valves springs coil packs injectors crank sensors cam sensors knock sensors everything else whats next i've been to 4 shops and not fixed yet but 1200 tied into it tryin to fix it

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    Visitor, May 05, 2011, 21:25

    I think it might be more than one injector, there known to be faulty, and faulty in pairs, so I would suggest replacing all your injectors...the same thing is happening to me...but for me I would get looong crank times before the engine would fire, so I checked the fuel pressure and found it to be leaking down, I then replaced the fuel pump, and re-checked the fuel pressure and it continued to leak down, so I checked the injectors and found three that were faulty, so I suggest checking them, and if you replaced one already, should continue to replace all...

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