1. #1

    2004 Grand Cherokee 4.0L random multiple misfire P0300-1,2,3,4,5,6

    The problem: The engine Idles fine however while under load (accelerating) the check engine light flashes and eventually the engine sputters out as if it were only firing on 2 cylinders and was horribly out of timing. Almost a complete loss of power and usually happens over 55 MPH and above 3000 RPM. When I turn the engine off while moving and then back on, the problem goes away for about a minute and then comes back. Its all intermitent though, sometimes it runs like a dream.

    List of Codes: P0340, P1490, P1489, P0300, P030X-1,2,3,4,5,6, and P1391

    What I've done: replaced...

    -Spark plugs (copper core Champions)
    -Ignition coil
    -All 4 O2 sensors (Denso)
    -Fuel Pump (Delphi - It could be bad, I can hear it come on and there is a mostly constant high pitched humming coming from it. I only replaced it because I was having some starting issues and a mechanic said I had low fuel pressure. The starting problem was solved.)
    -Fuel Filter (Fram)
    -Camshaft Position Sensor and Synchronizer (Duralast - It was professionally installed but I am not confident in their work because that P0340 code came back a while after they replaced it.)
    -Check for vacuum leaks and I found none. Missed one perhaps?

    Any help you guys could give me would be awesome. I'm out of ideas unless the mechanic didn't do the CPS right. I've thought about the Crankshaft PS but I thought that really only affected the idling. I've also thought maybe the PCM since it works for about a minute after restarting the Jeep. But let me know what you guys think.

  2. #2

    Re: 2004 Grand Cherokee 4.0L random multiple misfire P0300-1,2,3,4,5,6

    I dont know
    no more jeeps at this time. next time it will be a cj with a v8

  3. #3
    Join Date
    Feb 2009
    Location
    Dayton Ohio Area
    Posts
    5,156
    Should be using double platinum plugs.
    P0340 is the cam sensor..airtex/wells. Is OEM
    p1490 is the fan relay. Replace it.
    P1391 crank sensor. Replace it. OEM airtex/wells make sure it has the paper spacer on it when you install.
    Last edited by JPNinPA; 03-18-2016 at 07:33 PM.
    "Never look down on anybody unless you're helping him up" - Jesse Jackson

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