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  1. #1
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    Misire on startup

    Hello all!

    I have a 2005 Chrysler 300c, and for the past few weeks, nearly every time I start it after sitting for a few hours, I get a terrible misfire. It only last for maybe a minute and a half tops. The cel will flash the whole time, and sometimes stay on, but the only code is random multiple cylinder misfire. It smells really strongly like gas when it's doing it too. I had originally thought fuel pump failing, but with the smell of gas, I'm not so sure?

    If anyone has any ideas, or maybe experienced the same thing and figured out the cause, please chime in. Any input is greatly appreciated!!!

    Thank you!!

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  2. #2
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    Pull the plugs and see what they look like.
    Smell of gas could be from a leaking injector, or from that misfire.
    What does the engine oil smell like?


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  3. #3
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    Same as above. Pull plugs. See if there is odd signs, excessive oil etc.
    Does it puff smoke?


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  4. #4
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    X3 as above. If you suspect the injectors, before ripping into everything, you may want to try a good injector cleaner first. Also, are you always using a good top tier fuel or some "fly by night" fuel from a cheapo place??
    06 300CSRT8, Comp cammed, 85mm TB, HP/DS Tuners, 06 Jeep GCO and 05 Magnum RT (5.7's) both modded almost the same, MDS "ON" Lt, Fumoto Drain Valves, BT Catch Cans, SRT8 CAIs, AFE Filters, Sonnax Trans Line Press Booster, SC, DS and HP Tuners, Transgo Shift Kit, ARH Long Tube Hdrs w/3 in Magnaflow/Xlerator AP Exh Sys, Bilsteins, SRT Springs/Sways, Cust Eng Cvrs, SRT8 frt/rear bumpers, FRI Sidewinder Cams advanced (Jeep 6*/Maggie 10*), 6.1 valvetrain, SLP 25% UD Pulley, BBK and Arrington 90mm T-Bodies, SOS Ign Coils,TEA ported/milled heads w/new valve seats, SRT Reps.

  5. #5
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    First...what DTCs have been set?

    Second...did you alter anything prior to the problem showing up?
    Last edited by Hemissary; 12-02-2019 at 08:18 PM.
    2005 Magnum RT---Viper Venom Red----440ci Aluminum block----Short Runner Valve Intake--410mm BAER 6S Monoblock Extreme--Eibach Multi-Pro 2

    Custom--Grille Work--Hood--Headlights--Side View Mirrors--Rear Spoiler--Rear Diffuser--SRV Control System--Turbine Wheels

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  6. #6
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    I'll pull the plugs as soon as I get a chance. I know they're due for a change, they're copper, and they've got about 50k on them. I always run premium fuel, and 95% if the time I get it from Loaf and Jug.

    The only DTC that has stuck was P0300, and only twice, usually it just flashes the whole time and goes off when it stops.

    Could a bad cat cause this? I've gotten a DTC for O2 sensor on bank one, usually it's bank 1 sensor 1, but I have gotten a bank 1 sensor 2 also. The O2 DTC's don't come on when missing, they come on when I'm driving. I had a Envoy years ago that had a plugged cat, and that thing you couldn't even drive it ran so poorly. My car still runs great after the misfire clears up, no hesitation or loss of power. I have noticed lately though that when I hammer on it on the highway to pass, it stinks really bad kind of like sulfur, which I don't really remember it doing before.

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  7. #7
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    Forgot to mention, no recent changes leading up to this. I changed the fuel pump about 8 months ago, water pump about 6, and thermostat about 4.

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  8. #8
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    Given P0300 is a general misfire DTC that isn't calling out any one (or more) cylinders, there's many potential root causes. The FSM points to (in my suggested order of importance): EGR valve functionality, camshaft position sensor, PCM, O2 sensor(s), catalytic converter(s), high tension leads, sparkplugs, fuel injector(s) / wiring, coilpack(s) / wiring.

    Plugs just don't go bad, nor does control wiring, converters, high tension leads or coilpacks...unless you've continued(!) to drive it for months - while the problem persists.

    Another clue might be switching from open loop to closed loop...
    2005 Magnum RT---Viper Venom Red----440ci Aluminum block----Short Runner Valve Intake--410mm BAER 6S Monoblock Extreme--Eibach Multi-Pro 2

    Custom--Grille Work--Hood--Headlights--Side View Mirrors--Rear Spoiler--Rear Diffuser--SRV Control System--Turbine Wheels


  9. #9
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    Quote Originally Posted by Hemissary View Post
    Given P0300 is a general misfire DTC that isn't calling out any one (or more) cylinders, there's many potential root causes. The FSM points to (in my suggested order of importance): EGR valve functionality, camshaft position sensor, PCM, O2 sensor(s), catalytic converter(s), high tension leads, sparkplugs, fuel injector(s) / wiring, coilpack(s) / wiring.

    Plugs just don't go bad, nor does control wiring, converters, high tension leads or coilpacks...unless you've continued(!) to drive it for months - while the problem persists.

    Another clue might be switching from open loop to closed loop...
    Thank you for the suggestions!! It's been going on for a little bit more than a month now, a few days last week being the worst. Now since I've posted this, of course it hasn't been doing it!

    Do you think the O2 DTC's that I've been getting may have anything to do with it? They're way less often than the misfire, but seem to be getting more frequent, maybe once a week since the misfire started. Thing with them is, they don't show up on startup, usually while cruising.

    How would one switch from open to closed loop? I have a Diablosport i1000, and can purchase the AlphaODB app if needed.

    Thank you!!

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  10. #10
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    Quote Originally Posted by JD323 View Post
    Thank you for the suggestions!! It's been going on for a little bit more than a month now, a few days last week being the worst. Now since I've posted this, of course it hasn't been doing it!

    Do you think the O2 DTC's that I've been getting may have anything to do with it? They're way less often than the misfire, but seem to be getting more frequent, maybe once a week since the misfire started. Thing with them is, they don't show up on startup, usually while cruising.

    How would one switch from open to closed loop? I have a Diablosport i1000, and can purchase the AlphaODB app if needed.

    Thank you!!

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    You're welcome :^)

    Read / learn the PMC / other modules startup process the PCM Open / Closed Loop (OL / CL) sections within the Service Manuals we all have the luxury of downloading...

    After startup, preset timing and A/F values are in-play until many other PIDs (and their values) triger the PCM to enter closed loop control. The O2 sensors are just four PIDs that must be functioning properly and relaying expected raw data - prior to entering CL. OL operation appears more likely problematic...

    Have you altered any engine operating parameters?
    2005 Magnum RT---Viper Venom Red----440ci Aluminum block----Short Runner Valve Intake--410mm BAER 6S Monoblock Extreme--Eibach Multi-Pro 2

    Custom--Grille Work--Hood--Headlights--Side View Mirrors--Rear Spoiler--Rear Diffuser--SRV Control System--Turbine Wheels


  11. #11
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    I have the service manual, I will check it out for sure!

    I am running the Diablosport 91 tune. I already had the tuner from my previous Magnum, so the first thing I did when I got it was load the tune. It'll be 2 years in March. I did alter some things like temp for 180° stat and throttle boost and tire size, but nothing other than whatever the Diablosport canned tune does to the engine parameters.

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