Misire on startup

[JD323]

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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[DBL.DWN]

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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[Newoldchallenger]

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


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[magnuman]

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??

[Hemissary]

First...what DTCs have been set?

Second...did you alter anything prior to the problem showing up?

[JD323]

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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[JD323]

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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[Hemissary]

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...

[JD323]

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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[Hemissary]

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 / follow the PCM / other modules startup process, 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?

[JD323]

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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[JD323]

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?

Car started acting up again. Using the Torque app, I can see that as soon as it switches from open to closed loop it starts misfiring. It will continue to misfire for 30 seconds to a minute and smooth out. I've gotten a code a couple times for O2 bank 1 sensor 1 but not every time. If I watch the O2 data, it's not at all like it is for bank 2 sensor 1. Bank 2 sensor 1 goes up and down on the chart like it's supposed to, and bank 1 sensor 1 is more of a low line with lots of short spikes in it. Could this indicate a bad O2 sensor on bank 1? If it was a bad sensor, shouldn't it throw a code every time?

I did replace the EGR valve because it was also "hunting" while idling. The hunting issue went away after replacing the EGR, but the misfire problem is still there. I hate to just start replacing parts, but would it pay to change out the sensor on bank 1?

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[Hemissary]

Car started acting up again. Using the Torque app, I can see that as soon as it switches from open to closed loop it starts misfiring. It will continue to misfire for 30 seconds to a minute and smooth out. I've gotten a code a couple times for O2 bank 1 sensor 1 but not every time. If I watch the O2 data, it's not at all like it is for bank 2 sensor 1. Bank 2 sensor 1 goes up and down on the chart like it's supposed to, and bank 1 sensor 1 is more of a low line with lots of short spikes in it. Could this indicate a bad O2 sensor on bank 1? If it was a bad sensor, shouldn't it throw a code every time?

I did replace the EGR valve because it was also "hunting" while idling. The hunting issue went away after replacing the EGR, but the misfire problem is still there. I hate to just start replacing parts, but would it pay to change out the sensor on bank 1?

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Good job; in the toubleshooting section of the FSM, it will give you expected / max operating range. It will also tell you the parameters that activate a DTC and how many key cycles must be free of the dame DTC before it clears automatically.

[JD323]

Here's a screenshot of the O2 data during the misfire. The straight lines on the bank 1 sensors is during the misfire. Wher they start to move again is right where the missing stops. Any ideas what could be causing this?

Misfire O2 data Imgur: The magic of the Internet



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[JD323]

Here's a screenshot of my injector pulse data, notice cylinder 5 is way down compared to the rest. This is all the time thought, even when it's running smoothly. I plan to swap it out with another to see if the injector is bad. Any ideas on this one too?

Injector data Injector data - Album on Imgur

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