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Thread: Misfire problems

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    Full Access Member Mopar1973Man's Avatar
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    Default Misfire problems


    Hey guys I'm wondering if anyone has a way of dealing with a misfire problems??? Here is what has been done. This is on my Mom's 1996 in signature below.

    I've been getting a weird misfire that is random. It will throw the CEL Light and when you check the flash codes you get a 43 (I think...) But when you hook a code reader you get a...

    P0300 - Random/Multiple Cylinder Misfire Detected
    P0306 - Cylinder 6 Misfire Detected

    Always the same cylinder too...

    What has been done...
    New Cap & rotor, New Spark plug wires, NGK Spark plugs, New injector on Cylinder #6, New oxygen sensors (front & rear).

    Please help if anyone got any ideas...

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    Full Access Member holtzer1's Avatar
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    step one...get rid of ngk plugs...its not a honda. ONLY champion plugs on a mopar product. that could be part of it. what kind of vehicle are we dealing with here? i could shed more insight if i knew what it was. year, make, model and engine size.

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    Full Access Member Mopar1973Man's Avatar
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    As for make and model its in the signature "Mom's Truck"

    Mom's Truck - 1996 Dodge Ram 1500 - Magnum V8 360 5.9L, Auto, 4x4, SWB, 3.55 Gears, 15.36 MPG, 131K+ Miles, 5,500# - "Slash"

    As for the NGK plug a local shop told me they where better than the Champion's that were in the truck. The first time I had the problem I had Autolites, then changed to champion plugs, now to NGK...

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    Full Access Member holtzer1's Avatar
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    well, this is what i do for a living....especially in chryslers...use ONLY champion plugs. i have seen misfires happen with brand new plugs...that werent champions.
    ngk=import
    champion=chrysler
    ac=gm
    motocraft=ford


    now for other possible problems.....
    could be.....
    wiring...as much as youd hate to hear it..could have a break in the injector circuit
    could be a pcm shitting the bed
    i would check compression on that cylinder....
    but with the "random cylinder misfire" i would look more towards the ignition side of the system. does it do it more when damp or raining out? could be a bad cap. the ign wires arent rubbing anything are they? another possible cause is. inside the distributor, the pickup plate is riveted to a piece of plastic. i have seen many that have the cam sensor plate wallowed out the plastic rivet deals and it gets a funky cps signal(which is what fires the injectors)
    check that stuff out and see where it ends up.

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    Full Access Member Mopar1973Man's Avatar
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    i would check compression on that cylinder....
    Done... 130-140 PSI all the way around. Also smooth and steady Vacuum... No ticks (bad valves)

    but with the "random cylinder misfire" i would look more towards the ignition side of the system. does it do it more when damp or raining out? could be a bad cap. the ign wires arent rubbing anything are they?
    When I mean random it could be 2K-3K miles till the next time it start to mis-fire. But it always comes back with the same error. P0306 - Misfire #6 Cylinder. I take it out and run it hard and then I can clear the errors. The stay cleared for another 3K or so miles.

    New Cap, Rotor, and wires... All wire are sepearated not rubbing and not touch hot manifolds.

    i have seen many that have the cam sensor plate wallowed out the plastic rivet deals and it gets a funky cps signal(which is what fires the injectors)
    check that stuff out and see where it ends up.
    I'll check that out... It'll be a day or two but I'll check it out...

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    Full Access Member holtzer1's Avatar
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    other than that...youve got a tricky one on your hands....i'll keep racking my brain for other common possibilities.

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    Shane 96_Bear's Avatar
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    I had the same problem with the 95 1500 5.9 I had. My buddy at the dealership told me to reroute the coil wire by its self to stop a bleed over did it havent had a miss fire since. Just my .02
    '96 F350. Crew Cab, 4x4, At, Warn hubs, SRW, 3.55's, A Pillar Triple Gauges AutoMeter SportComp, Pyro, Boost, Trans Temp, Hypermax Dp, Dual 28,000lb trans coolers stacked plate,5" Chrome stacks, (No kitty CAUSE I WANT TO RUN WITH THE BIG DOGS),4 corner strobes,Meyers 7'6" plow, Open air intake HOME MADE

    "IF ITS TO LOUD YOUR TO OLD"

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    Full Access Member Mopar1973Man's Avatar
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    As a matter of fact it just came back again... Its been about 4 months without the problem and now its back again...

    I took the truck out and ran the trash out of it... Drove it like I stole it... And the miss is gone... I got to clear the error codes now...

    As for the bleed over the coil is mounted on the front of the engine next to the alternator and is routed away from the other wires...

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    Buzzard Pilot PackRat's Avatar
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    Pull the valve covers, and check for a broken valve spring.

    As stupid as it sounds, one time, I heard of an irregular miss, that couldn't be tracked down. After doing all the regular R&R stuff, the mechanic noticed an irregularity on the scope. On a hunch, he pulled the valve covers, and found a spring with about a turn broken off the top.
    Being a nice guy has gotten me far in life.....

    Far in debt, and far from sanity.

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    Reqistered User highest_vision's Avatar
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    Have you pulled #6 plug out when it starts to misfire? Compared it to any others? Maybe scoped cyl 6 and compare to others when it happens vs after you 'clean it out?' Maybe change all your plugs now (since you have it straightened out) and check them at maybe 2k or an interval you feel is relavant.
    James

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    Full Access Member holtzer1's Avatar
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    you could also save some time, instead of pulling the valve covers, just hook a vacuum gauge to manifold vacuum port....with the engine running you should see a steady vacuum reading. if you have a rapidly fluctuating reading..+/- 5 or more psi at idle...you have a valve problem, be it a burn valve, or broken valve spring.

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    Full Access Member Mopar1973Man's Avatar
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    Ok... Here is the information I can give...

    Vacuum is steady right around 18"
    Compression test 130-135 PSI all the way around
    Spark plugs are all like out of the box new yet... No deposits on them. I even had them re-tested for spark pattern.
    Replace #6 injector
    Replaced all plug wires (twice now)
    Replaced all spark plugs (3 sets so far)
    Replaced Cap and Rotor

    This problem is random... Might leave for about 3-4 months and come back. It gets driven very little. About 3-4K a year...

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    Shane 96_Bear's Avatar
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    Check the coil maybe it has a hairline crack when hot or damp maybe causing the problem
    '96 F350. Crew Cab, 4x4, At, Warn hubs, SRW, 3.55's, A Pillar Triple Gauges AutoMeter SportComp, Pyro, Boost, Trans Temp, Hypermax Dp, Dual 28,000lb trans coolers stacked plate,5" Chrome stacks, (No kitty CAUSE I WANT TO RUN WITH THE BIG DOGS),4 corner strobes,Meyers 7'6" plow, Open air intake HOME MADE

    "IF ITS TO LOUD YOUR TO OLD"

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    Full Access Member holtzer1's Avatar
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    had one in yesterday, so this is what reminded me to post back

    remove the air cleaner off the throttle body, take a flashlight and open the butterflies, look into the intake...if there oil in the bottom of the intake planum you have a blown lower intake pan gasket...very common on the older rams as they had fiber gaskets instead of the new metal ones. that could very well be the problem. i had a van come in with a #2 cylinder misfire, guy had done a tune up himself...but it still came back with a #2 misfire...he also had a slight spark knock under load. i checked the lower intake gasjket, and sure enough, there was oil in the bottom of the intake(air plenum). when i got the intake off, i found a blown gasket and the bolts holding it on were all loose.

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    Full Access Member Mopar1973Man's Avatar
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    Well so far the problem came back for one day and left again... I haven't had a problem with it for about 2 months now...

    So the idea of the gasket isn't it. That would be constant... Not to mention It never uses a drop of oil in 3K miles!

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