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Discussion Starter #1
2010 jeep patriot sport AWD 2.4L. was missing bad and had p0300 code. replaced both camshaft sensors, crankshaft sensor, sparkplugs and 1 coil pack on the cylinder that was misfiring. cylinder 1 is the one misfiring. i swapped the fuel injectors of cylinders 1 and 2 to see if it was an injector and cylinder 1 still misfired. while it is running with the misfire i can remove the plug to the coil pack on cylinder 1 and the motor stays the same, any other cylinders the motor dies when plug removed. i am at my wits end please help.
 

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2010 jeep patriot sport AWD 2.4L. was missing bad and had p0300 code. replaced both camshaft sensors, crankshaft sensor, sparkplugs and 1 coil pack on the cylinder that was misfiring. cylinder 1 is the one misfiring. i swapped the fuel injectors of cylinders 1 and 2 to see if it was an injector and cylinder 1 still misfired. while it is running with the misfire i can remove the plug to the coil pack on cylinder 1 and the motor stays the same, any other cylinders the motor dies when plug removed. i am at my wits end please help.
sounds like a valve is burnt or not closing, need to take compression test.
 

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Valve is a good bet, but ... Since spark plugs were changed, I would also check the spark plug and associated parts again. Check the plug (the new plug could always be faulty and switching with another from another cylinder can cause problems as well - but you could always switch two to see if the fault code travels) for cracked ceramic or damaged threads (indicating cross threading), check the spring on the boot to make sure it isn't broken or damaged, check for flashing or damage to the coil itself. Check the little rubber seal and that the plugs are snug. Then check for frayed wiring.

Do this before looking for a burnt valve.

PS: also, you may need to do a cam/crank sensor relearn if this all happened after the sensors were changed. And plugs should be replaced as sets. Not one individual if possible unless they were all brand new.

PPS: also, if you have a scan tool with live data, see how often it misses. How many miles/kilometres do you have on the car?
 

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Discussion Starter #5
have tested spark plugs with the other cylinders. all are new. the original problem has not been resolved with all the parts that have been replaced. i am leaning toward the pcm module as it has to be electrical. i can drive it down the road and it will start missing after 20-30 seconds. pull off turn ignition off, restart and the problem is gone and car runs fine for 20-30 seconds and i can repeat this process all day and it does the same thing. does not matter if i am running it hard or it is sitting idling. i have also reset the adaptive memory. it has 150,000 miles has been well maintained. i have tried to do the relearn process but am unable to exceed 55 mph in the 20-30 seconds that the car runs good.
 

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There is a relearn for cam/crank sensors. Did you do that, or just reset adaptive memory (you can do it with a more advanced scan tool)? Also, is it possible that one of the sensors you changed was bad? Have you checked timing? Could it be that the chain is slipping?

I'm guessing that you don't have any new codes?
 

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The p0300 code you state is for multiple cylinder misfires. P0301 is for cylinder #1 misfire. Something doesn't add up.

The lengthy factory service manual diagnostic sequence for P0300 starts out with this statement:

Misfire may occur and may not be caused by component failure. Any of the following conditions can cause a misfire:
•Worn serpentine belt
•Misalignment or binding water pump, P/S pump or A/C compressor pulleys
•Improper CKP, CMP, MAP, or TP Sensor mounting.
•Poor connector/terminal to component connection for CKP sensor, CMP sensor, MAP sensor, TP sensor, fuel injector, ignition coil, etc.
•Corroded PCM power or ground circuits.
•Vacuum leaks.
•Restriction in the air induction or exhaust system.
•Internal engine component malfunction.
•Moisture on ignition system components
•Insufficient fuel
•Low quality fuel
•Manual transmission bog
•Towing overload

These are the systems (not parts) that the service manual goes through step by step diagnostics:
- FUEL DELIVERY SYSTEM
- IGNITION COIL, WIRING, OR CONNECTORS
- ECT SENSOR, WIRING, OR CONNECTORS
- MAP SENSOR, WIRING, OR CONNECTORS
- O2 SENSOR, WIRING, OR CONNECTORS
- ENGINE MECHANICAL SYSTEM
- POWERTRAIN CONTROL MODULE (PCM)

Not trying to be a jerk here. Your parts swapping might be in vain if you haven't really identified the problem. Just sayin'............ Lately, my only input on threads like this is that you should buy a basic scan tool (under $100) and factory service manual.
 

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Treegrower +1
 

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Discussion Starter #9
not trying to be a jerk either but i have both items you suggested. scan tool and manual. it does seem that you are not understanding the issue. it runs perfectly well for 20 to 30 seconds and then cylinder one starts misfiring. it is like the control module tells it to stop firing on cylinder one after that short time. this is consistent. it happens every time after a startup. the code jumps between p0300 and p0301. i do thank you for taking the time to reply.
 

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Well, shoot. I would not have posted the above if I knew that you had ferreted out all the diagnostic procedures and still was at a loss. I have no experience with your p0300/301 code and am flabbergasted at the number of things that can throw these DTC's. And then, the repair procedures are so complicated. For instance, I didn't know that the replacement of an O2 sensor (a possible cause here) requires clearing the Ram data for a relearning process to occur.

I once had a "transmission" problem (NO codes thrown) that turned out to be a $28 throttle speed sensor that no one could diagnose (Caravan). I feel your pain.

I now comprehend your symptoms, but don't have any good advice to fix it. I'll bow out as gracefully as I can.
 

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Misfires could still be the result of a lean fuel mixture. Have you checked your fuel pressure? The fact that it keeps swapping means that it could be something borderline. The you could have one cylinder that's going lean and the rest might have better compression/injectors/etc that are making them only flip-flop on the borderline

How are your fuel trims? What is your A/F ratio on live data?
 

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i am leaning toward the pcm module as it has to be electrical...
Could be.

According to the manual (see attached) one end of the coil is tied to 12v through the TIPM and the other is brought to ground by the PCM. If possible, I'd check both the signal and 12v at the end of the connector that plugs into the coil pack.
 

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Discussion Starter #13
just put a meter on the number 1 pigtail. 12 volts and 3.65 volts when switch is on but not running. when it is running and missing the voltage for number 1 pigtail is 14.2 and 3.65 never changes. on number 2 pigtail it is 14.2 and the signal bounces around from 3.6 to 4.8. hopefully that will help narrow it down for someone.
 

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Does #1 pigtail bounce around from 3.6 - 4.8 like #2 does when it's running right and then 20-30 sec later it goes to 3.65?

If you have a 12v test light you could hook that up across the pigtail and see if it blinks then stops.

Does outdoor temperature seem to make a difference, works better/worse when hot or cold?
 

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Discussion Starter #15
during the first 20+ seconds the cylinder 1 signal bounces around just as the rest but after that 20 seconds it stays at 3.65 volts dc and does not move.
 

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Any resolution on this?

I'm having the same issue except cyl 1 & 4 are causing trouble. I've also replaced the spark plugs, coils, crank sensor, swapped injectors from working cylinders, and replaced fuel pump. Same issue. I'm only getting the p0300 code thrown.

I also can't get to 70 mph to do the relearn procedure.

Any help?
 

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Sorry for the delayed reply.

Turns out I’m having the same readings as @gbrogdon on this. The readings on my trouble cylinders are 14 and 3.65 while running and the others show 3.6-4.8v while running.

Is my best course of action taking it to a dealer and having them reset the PCM?
 
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