Random Misfire 2007 Liberty

ArmySloth

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Please help! I have a 2007 Liberty with 145000 miles. I absolutely love this Jeep and it has been very reliable up until recently. While driving home, going approximately 25 mph, the Jeep suddenly started misfiring and running like ****. Idle was rough and CEL started blinking. I took it and got it scanned and was told it needed new ignition coils. After replacing the coils and plugs, it still ran like **** which led me here. I read so many of the discussions here and began attempting to diagnose the issue. So far the battery has been replaced, coils have been replaced, new plugs, removed tested and cleaned injectors, removed alive covers (nothing overtly concerning), replaced camshaft position sensor, replaced crankshaft position sensor, and O2 sensors. Examined wiring and tested connectivity between individual coil and injector plugs and PCM harness. Still runs like ****, engines smoothes out a little bit above 3000 rpm but chugs below 3000 rpm. After getting it all back together, I took it to clear the codes and scan again. I have attached the photos from the scanner. I drove it for 15 miles carrying speeds with no change. Please let me know your thoughts.
 

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Johnny O

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Please help! I have a 2007 Liberty with 145000 miles. I absolutely love this Jeep and it has been very reliable up until recently. While driving home, going approximately 25 mph, the Jeep suddenly started misfiring and running like ****. Idle was rough and CEL started blinking. I took it and got it scanned and was told it needed new ignition coils. After replacing the coils and plugs, it still ran like **** which led me here. I read so many of the discussions here and began attempting to diagnose the issue. So far the battery has been replaced, coils have been replaced, new plugs, removed tested and cleaned injectors, removed alive covers (nothing overtly concerning), replaced camshaft position sensor, replaced crankshaft position sensor, and O2 sensors. Examined wiring and tested connectivity between individual coil and injector plugs and PCM harness. Still runs like ****, engines smoothes out a little bit above 3000 rpm but chugs below 3000 rpm. After getting it all back together, I took it to clear the codes and scan again. I have attached the photos from the scanner. I drove it for 15 miles carrying speeds with no change. Please let me know your thoughts.
What plugs you using?
 

ArmySloth

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Not yet. I was going to look at that next, just haven’t had a chance yet.
 

Ksat

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Post some live data PIDs and make sure to include short and long fuel trim. Does your scanner have mode 6? Also, what brand (upstream) oxygen sensors did you use? Don't drive the car with the CEL flashing, unless you don't mind burning up the cat converters.
 

Duster

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I had the same thing twice. Well I don't remember the codes. But after replacing the coils on those plugs, I got mad and replaced the injectors and that was the issue both times. I've had a coil riding around under the seat for probably 100K miles.

I have replaced 2 injectors so far.

I'd check the coil wiring and if you don't find anything pick up an injector or two and swap them on the affected cylinders. I think at least one of the two times I had to have it running with the retaining nuts off the coils and pull them up one at a time until I found the cylinder that made little to no change.
 

LibertyTC

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Fuel Pressure psi test it. Key on reading, Started & running, and leak down psi after jeep off for 15-20 min.
Can you confirm that you are using NGK ZFR6F-11G spark plugs and that the gap is set to .040 inch?
 

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ArmySloth

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Post some live data PIDs and make sure to include short and long fuel trim. Does your scanner have mode 6? Also, what brand (upstream) oxygen sensors did you use? Don't drive the car with the CEL flashing, unless you don't mind burning up the cat converters.
Ksat,
Thank you for your response. I am leaving it parked for now to avoid further damage. I believe the o2 sensors where Walkers. I will have to get back to you with the numbers when I get a chance.
 

ArmySloth

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Fuel Pressure psi test it. Key on reading, Started & running, and leak down psi after jeep off for 15-20 min.
Can you confirm that you are using NGK ZFR6F-11G spark plugs and that the gap is set to .040 inch?
LibertTC,
Thank you for your response. Yes the plugs are NGK ZFR6F-11G gapped .41 in. I will post the fuel pressure reading when I get a chance.
 

ArmySloth

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I had the same thing twice. Well I don't remember the codes. But after replacing the coils on those plugs, I got mad and replaced the injectors and that was the issue both times. I've had a coil riding around under the seat for probably 100K miles.

I have replaced 2 injectors so far.

I'd check the coil wiring and if you don't find anything pick up an injector or two and swap them on the affected cylinders. I think at least one of the two times I had to have it running with the retaining nuts off the coils and pull them up one at a time until I found the cylinder that made little to no change.
Duster,
Thank you for your response. When I removed the injectors to test and clean them, I purposely switched injectors 1 and 6 with 2 and 3 to see if the problem followed the injectors. This was not the case though.
 

Duster

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I assume you moved the coils around too. Etc.

I think it is time to start looking at the wiring for #1 and #6
Running voltage and then ohm from coil connector to PCM connector.

I hope you find it there because if not that leaves the PCM or compression... and I really hope it isn't compression.

Let me know if it's the PCM and I will dig up where I got mine from. That place was the only one I could find that had a decent price and it was plug and play ready to go when it arrived... otherwise the PCM is a lot or you get it used, and then you have to pay a lot to get it working because it's not plug and play. Dealer or somewhere on the mopar network because it needs the vin, mileage, quick learn, security programming, etc, etc.
 

ArmySloth

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After significant diagnostic work, the conclusion is PCM. I appreciate all the advice and help y’all shared!
 

ArmySloth

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I assume you moved the coils around too. Etc.

I think it is time to start looking at the wiring for #1 and #6
Running voltage and then ohm from coil connector to PCM connector.

I hope you find it there because if not that leaves the PCM or compression... and I really hope it isn't compression.

Let me know if it's the PCM and I will dig up where I got mine from. That place was the only one I could find that had a decent price and it was plug and play ready to go when it arrived... otherwise the PCM is a lot or you get it used, and then you have to pay a lot to get it working because it's not plug and play. Dealer or somewhere on the mopar network because it needs the vin, mileage, quick learn, security programming, etc, etc.
Thank you Duster! Turns out it is the PCM. If you have any recommendations, they would be greatly appreciated.
 

A. Sandoval

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Please help! I have a 2007 Liberty with 145000 miles. I absolutely love this Jeep and it has been very reliable up until recently. While driving home, going approximately 25 mph, the Jeep suddenly started misfiring and running like ****. Idle was rough and CEL started blinking. I took it and got it scanned and was told it needed new ignition coils. After replacing the coils and plugs, it still ran like **** which led me here. I read so many of the discussions here and began attempting to diagnose the issue. So far the battery has been replaced, coils have been replaced, new plugs, removed tested and cleaned injectors, removed alive covers (nothing overtly concerning), replaced camshaft position sensor, replaced crankshaft position sensor, and O2 sensors. Examined wiring and tested connectivity between individual coil and injector plugs and PCM harness. Still runs like ****, engines smoothes out a little bit above 3000 rpm but chugs below 3000 rpm. After getting it all back together, I took it to clear the codes and scan again. I have attached the photos from the scanner. I drove it for 15 miles carrying speeds with no change. Please let me know your thoughts.
I had a random misfire situation after pulling the plugs on my 2012 liberty. The plugs had a carbon line on the ceramic. I finally realized that when replacing the plugs, use a dielectric gel on the ceramic and inside the plug boot. The problem no longer exists.
 

Ksat

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After significant diagnostic work, the conclusion is PCM. I appreciate all the advice and help y’all shared!

Did you get a replacement PCM for it? It seems odd the transistor drivers for 2 separate coils could go bad at the same time.
 

ArmySloth

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Ok, so the new pcm cam in and the Jeep starts right up and idles beautifully. However, now the ETC light is on and I have absolutely no throttle response. I will be contacting Car Computer Exchange tomorrow. While I do not know for sure, I am assuming it has something to do with how the pcm was programmed.
 

Ksat

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I'm assuming you didn't have a throttle issue when the other PCM was in there.

The '07s were the first year to use the ETCs. Just a stab in the dark here, but your replacement PCM may have come out of a vehicle prior to that year which didn't have that feature.
 

Duster

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Yeah mix up I think. Nothing to worry about. They will probably be like dang sorry, lets exchange.

I used All Computer Resources and had no issues other than they are just like all of the other places and can't possibly know everything about every model.

I had to send in my VIN and mileage, etc. Fired right up and rolled. No ETC light or anything.
 
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