Multiple Cylinder Misfire Codes

[lrb6805]

Hey all,
I recently got a CEL that Ive cleared and has come back. It started when we got our first cold spell here in Texas. I am currently getting codes for:

P0300 (Random/Multiple Misfire)
P0301 (Cylinder 1)
P0304 (Cylinder 4)

It doesn’t seem to be running any rougher that Ive noticed, maybe a little bit more rumble while idling. I am getting worse gas mileage though.

I just read through some of the misfire threads but they all seem to have only one Cylinder effected. Is this a symptom of the coil rail?

I recently just put a bottle of SL-1 through the system, could this have caused it? Ive used the redline about 2 times prior and have never had an issue before.

2006 LJ 6 Cylinder 4.0, 98K miles
Spark plugs changed to iridium ones last summer


Sent from my iPhone using Tapatalk Pro

 

[Jerry Bransford]

Does it run better or worse when the engine is cold?

 

[lrb6805]

Does it run better or worse when the engine is cold?

I wouldn’t say it runs bad cold, but it definitely gets better as it warms up. Really the only thing i notice if the engine is cold/warm is the start-up. Some of the start-ups have been kind of cringy when its cold.


Sent from my iPhone using Tapatalk Pro

 

[Jerry Bransford]

The engine running better as it gets warm destroys my thought that the misfires could be caused by a bad O2 sensor. Right now I'm at a loss for what is causing the misfires. Are your iridiums Autolite XP-985 plugs? Bosch plugs are known to sometimes cause problems in our Jeeps.

 

[lrb6805]

The engine running better as it gets warm destroys my thought that the misfires could be caused by a bad O2 sensor. Right now I'm at a loss for what is causing the misfires. Are your iridiums Autolite XP-985 plugs? Bosch plugs are known to sometimes cause problems in our Jeeps.

Yep, the autolite plugs. About a year ago I did a thorough tune up after buying it used. New sparks plugs, O2 sensors, TPS, ODPA, cleaned battery terminals. All using the high quality parts recommended here that are known to work well


Sent from my iPhone using Tapatalk Pro

 

[Jerry Bransford]

Kind of at a loss now, could maybe be a bad crankshaft position sensor. A bad CPS can give badly shaped signal pulses to the engine computer and cause it to indicate misfires.

 

[lrb6805]

So I ordered the CPS and it has come in (current uninstalled), but the code cleared itself this past weekend when I was driving for extended periods of time on the highway with cruise control set at about 75mph.

Now Im waiting to see if it will come back.

Does anyone have any idea what could’ve caused those codes to begin with? They happened during a cold spell in Texas (which isn’t even really that cold, it was just in the 30’s for a few mornings).

Could could slow ignition have caused the codes to pop up?

Also, is the CPS a sensor that can be cleaned to spruce it back up or can it only be replaced once it started to go bad or “get tired”?


Sent from my iPhone using Tapatalk Pro

 

[KCsTJ]

So I ordered the CPS and it has come in (current uninstalled), but the code cleared itself this past weekend when I was driving for extended periods of time on the highway with cruise control set at about 75mph.

Now Im waiting to see if it will come back.

Does anyone have any idea what could’ve caused those codes to begin with? They happened during a cold spell in Texas (which isn’t even really that cold, it was just in the 30’s for a few mornings).

Could could slow ignition have caused the codes to pop up?

Also, is the CPS a sensor that can be cleaned to spruce it back up or can it only be replaced once it started to go bad or “get tired”?


Sent from my iPhone using Tapatalk Pro

I have been fighting the same codes, P0300 random misfires
P0303 cyl #3 misfire
P0304 cyl #4 misfire

I tried many things, including a new oem crankshaft sensor last week, no luck.
Bit the bullet and ordered new oem valve springs from wermopar, should arrive this week, ill install and post the results.

 

[mots]

If the codes don't come back, I suppose it could have been a one off event, like some borderline bad fuel or something like that perhaps. Usually though we aren't this lucky, but I hope you are! The coil pack services 6 cylinders with 3 coils. Cylinders 1 and 4 would not be serviced by the same coil pack in your case, so I am guessing it's something common to all cylinders, like fuel pressure/quality etc.

I have been fighting the same codes, P0300 random misfires
P0303 cyl #3 misfire
P0304 cyl #4 misfire

I tried many things, including a new oem crankshaft sensor last week, no luck.
Bit the bullet and ordered new oem valve springs from wermopar, should arrive this week, ill install and post the results.

In your case, the coilpack does service cyls 3 and 4, so that would be suspect in my mind. Did you change that out for an OEM unit already?

 

[KCsTJ]

If the codes don't come back, I suppose it could have been a one off event, like some borderline bad fuel or something like that perhaps. Usually though we aren't this lucky, but I hope you are! The coil pack services 6 cylinders with 3 coils. Cylinders 1 and 4 would not be serviced by the same coil pack in your case, so I am guessing it's something common to all cylinders, like fuel pressure/quality etc.



In your case, the coilpack does service cyls 3 and 4, so that would be suspect in my mind. Did you change that out for an OEM unit already?

Im sorry, I should have told that my 97 is the 2.5L and it has a distributor, so no coil pack.
But some 97s had weak valve springs and mine looks like I got a bad batch, its got 169k miles anyway so another $90 and its got new oem valve springs.
That should put an end to my misfires. I'll know in a week.

 

[mots]

Im sorry, I should have told that my 97 is the 2.5L and it has a distributor, so no coil pack.
But some 97s had weak valve springs and mine looks like I got a bad batch, its got 169k miles anyway so another $90 and its got new oem valve springs.
That should put an end to my misfires. I'll know in a week.

Gotcha, I’m not familiar with that issue.

 

[Tmoran82]

I have a 2006 Rubicon 6cyl 4.0L when it’s cold out as well my engine cranks hard to start. I changed the cam sensor cuz of error code p0344 p0340 no luck. Bit the bullet got a new pcm 850 bucks later same issue. Checked all wiring all good. It was warm Saturday in NJ the morning cranked hard went got coffee left at noon and Jeep started right up engine light off. Sunday was cold engine light back on. All plugs are good all sensors are Mopar now last night it was cold left work and Jeep kept bucking like a limp mode at 35mph. 3 mechanics say it’s a mystery but it has to be something. I keep dumping money into this thing and it has to be something!!! What can I be missing. I’m no mechanic I just know basic car crap. I’m at a loss and I don’t know. Now if I clear the codes the Jeep has no issue till morning or Jeep sits in the cold. Any help please I’m in 1400 bucks with resolutions

 

[KCsTJ]

I have a 2006 Rubicon 6cyl 4.0L when it’s cold out as well my engine cranks hard to start. I changed the cam sensor cuz of error code p0344 p0340 no luck. Bit the bullet got a new pcm 850 bucks later same issue. Checked all wiring all good. It was warm Saturday in NJ the morning cranked hard went got coffee left at noon and Jeep started right up engine light off. Sunday was cold engine light back on. All plugs are good all sensors are Mopar now last night it was cold left work and Jeep kept bucking like a limp mode at 35mph. 3 mechanics say it’s a mystery but it has to be something. I keep dumping money into this thing and it has to be something!!! What can I be missing. I’m no mechanic I just know basic car crap. I’m at a loss and I don’t know. Now if I clear the codes the Jeep has no issue till morning or Jeep sits in the cold. Any help please I’m in 1400 bucks with resolutions

I think those codes refer to the camshaft position sensor.
I would consider installing a new Mopar camshaft position sensor and make sure it's genuine OE Mopar or problems will persist.