1. Random mis when driving and rough idle

    1996 Jeep Cherokee Jeep was running good figured it was time for a tune up with 297000 replaced cap roter plugs wires coil coil pick up iac fuel filter upgraded to Bosch 4 hole injectors o2 sensors switched back to original set up do to random cut out witch it never did before the tune up when driving sometimes it does it a lot sometimes it runs great I might miss 1 time in 10 miles or it might miss 20 times but just cuts out a split sec and goes back to running good any help would be great out of ideas beside cps it was throwing codes p0300 and p0301 after tune up

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  2. #2
    Join Date
    Feb 2009
    Dayton Ohio Area

    Random mis when driving and rough idle

    P0300 and P0301 are misfire codes. 301 denotes cylinder P0300 is random misfire. Little more broad for causes.

    What RPM do you idle at?

    What brand and part number plugs did you use?

    If only 301

    Verify it is always 301.
    Inspect TPS and IAC connections.
    Check for vac leak at cyl #1 by spraying TB cleaner or WD 40 water... around plug, injector and intake to head while idling and listen for rpm change.
    Inspect the boot is over the plug properly and not cracked or damaged. Might show as a burn mark on the plug ceramic.
    Inspect plug is seated and torqued properly.
    Inspect gap.

    Inspect injector has all gaskets. And no additional are left in intake.

    If all pan out ok swap injector 1 with 4 and plug 1 with 6. See if 301 becomes 304 or 306.

    Post back what you find along the way.

    Never look down on anyone unless you are helping them up - Jesse Jackson
    Last edited by JPNinPA; 05-01-2020 at 02:48 PM.
    "Never look down on anybody unless you're helping him up" - Jesse Jackson

  3. Re: Random mis when driving and rough idle

    I had a similar issue recently. On the 4.0 the number 1 plug wire makes a difficult transition within a couple inches of the plug. I had arcing from the wire to the adjacent bracket. I applied a couple wraps of silicone tape and problem solved. If you crank it up and look under the hood at night you might see it arcing.

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