New to KJ: CEL Misfire #4

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LibertyTC

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38k miles say what..?? poor thing..
Jeeps do not like sitting around, city driving, and being driven like a grandma.
Carbon builds up easily in slow mode and never gets hot enough to blow the dust out.
Fuel should be kept fresh every 30 days or add a good fuel stabilzer like StarTron Link: Star Tron Enzyme Fuel Treatment Gas Additive Small Engine
Next is a good fuel system cleaner Chevron Techron Concentrate will help clean things up including the backside of valves. 2 bottles to a full tank available at wallyworld.
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You have to then get the cats hot and I mean HOT to burn crap out!
Take it on a 100+ mile hwy run OD off/ON but get those revs up, even to the floor a few times up hills.
You will know when the cats get hot - smell a bit of rotten gas eggs LOL..
The Jeep Will say Thank You.. and run way better.
You will notice a difference after the 100 + miles.
 

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jeeper03

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When I first got my 2003 liberty it had a cylinder 2 misfire. I tried everything you are doing and more but nothing changed it. Then one day the rocker arm fell off on that cylinder so I pulled both valve covers and bought the tool to change all the lifters with the cams still on. Never have the misfire come back after replacing the lifters and it runs great now.
 

JasonJ

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IMO: just use the car. Get a fresh full tank of Higher octane fuel and drive the misfire out of it! Cause Carbon buildup causes misfires too!

try a quality fuel additive.

Octane adds a fairly significant amount of carbon into the combustion process. Running a high octane fuel without a high compression combustion to properly burn it all (because octane is harder to ignite) just adds to excessive carbon build up problems.

A lot of people get this backwards. Stems from the thinking that all "Premium" labeled fuels are better for all cars. Not so. The key is to use a top tier fuel (regardless of octane grade). It's the cleaning additives that matter more than octane rating and octane content per volume.
 

K9JEEP

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When I first got my 2003 liberty it had a cylinder 2 misfire. I tried everything you are doing and more but nothing changed it. Then one day the rocker arm fell off on that cylinder so I pulled both valve covers and bought the tool to change all the lifters with the cams still on. Never have the misfire come back after replacing the lifters and it runs great now.
This is the reading that has worried me. But I will try driving the heck out of it and see what happens. The oil was just changed before I got it but I want to put my own oil in and run it from there, I'll try to get out and drive it.

It could be in my head but when I got it back from the shop after them telling me it was fine it seemed to have more pep lol.

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K9JEEP

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So sure enough CEL just came back on. Filled up with some good gas right before. It seems I should invest in a scanner tool. Should I start with switching the injector?

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Logan Savage

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I'd swap the injector , spark plug & coil with another cylinder & see what happened .
 

K9JEEP

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Got a scanner and it's just P0300, so no code for a specific cylinder

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tjkj2002

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Octane adds a fairly significant amount of carbon into the combustion process. Running a high octane fuel without a high compression combustion to properly burn it all (because octane is harder to ignite) just adds to excessive carbon build up problems.

A lot of people get this backwards. Stems from the thinking that all "Premium" labeled fuels are better for all cars. Not so. The key is to use a top tier fuel (regardless of octane grade). It's the cleaning additives that matter more than octane rating and octane content per volume.

True for carb'd engines and OBDI engines,totally false for OBDII engines.

A tank of 91-93 premium gas will actually be very beneficial if driven very spirited(AKA drive it like you stole it).
 

K9JEEP

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Update.
I changed the oil and added the Techron fuel cleaner and went on a 60 mile drive through the canyons, I drove it like my GTI. Pulled up some long hills, tried to keep the revs up and it chugged along the whole way.
It seems that the CEL will come in when idling for a bit so I stopped at the top for 5 minutes and nothing so I drove back home and again let it idle in the driveway for 20 minutes and no CEL but I do feel a shake.
More reading says could be ASD relay also but I'll keep driving it to see what code comes next.

Snapped some pics at the top so you can see what we are working with
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JasonJ

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True for carb'd engines and OBDI engines,totally false for OBDII engines.

A tank of 91-93 premium gas will actually be very beneficial if driven very spirited(AKA drive it like you stole it).

I'd love to see the science and math behind this. No purple font here, if there is something different I would like to be educated on it.

I realize and am very much aware that OBD-II is a much more advanced computer system with a lot more fine control over the entire engine mgmt process, but I fail to see how adding a fuel which inherently has a higher quantity of Carbon containing compounds, burning in a standard compression engine does not contribute to an excess of Carbon being either accumulated in engine or blown out the exhaust.

Regardless of which engine it is burning in, higher octane fuel is more difficult to ignite. So what is so different about how OBD-II manages it's engine systems that makes this a non-issue?
 

K9JEEP

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Update:
I put all the original OEM coils back on except number 6, drove for a few miles no codes. Replaced number 6 coil with original OEM and when I warmed it up this morning it threw P0300 and P0304 x2. This is also the original cylinder that had a code. I cleared the code and drove the rest of the day.
I gave it another look over and I thought I heard some sort of hissing noise near the coolant resivior but could not find any cracked or damaged lines. I can still see the engine shake, I still feel a good shake in the drivers seat and the engine lookes to be having a little struggle when I look at that #4 side.

I can't help but think it has something to do with this engine sitting for possibly a year before I got it.

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tjkj2002

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I'd love to see the science and math behind this. No purple font here, if there is something different I would like to be educated on it.

I realize and am very much aware that OBD-II is a much more advanced computer system with a lot more fine control over the entire engine mgmt process, but I fail to see how adding a fuel which inherently has a higher quantity of Carbon containing compounds, burning in a standard compression engine does not contribute to an excess of Carbon being either accumulated in engine or blown out the exhaust.

Regardless of which engine it is burning in, higher octane fuel is more difficult to ignite. So what is so different about how OBD-II manages it's engine systems that makes this a non-issue?
Premium does not have "higher quantity of carbon containing compounds",it's just resistant to higher combustion temps(IE higher compression).

premium also in general much better refined fuel and has in general better additives.

Under "spirited" driving it will let the PCM lean the fuel/air mix for slightly better performance without making more pollution.This applies to towing and offroad use also since your placing your engine under far more stress and building more heat then normal driving.With that added heat you get alot of heat soak which can and still does cause "vapor lock" in modern FI engines.I have to use premium or I get pinging when I venture above 10,000 feet.

The PCM will configure the timing and injector pulse width to run it and under normal driving can slightly improve mpg's like a partially plugged air filter will on a OBDII controlled engine.
 

JasonJ

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Premium does not have "higher quantity of carbon containing compounds",it's just resistant to higher combustion temps(IE higher compression).

I hear ya, but you do know HOW they achieve that ignition resistance, right? It's a chemical compound called octane. C8H18. Eight carbon atoms linked together, i.e a hydrocarbon.

That carbon has to go somewhere when it's broken apart by the combustion process. Either accumulate in the engine, or out the exhaust; usually a little of both.
 

tjkj2002

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I hear ya, but you do know HOW they achieve that ignition resistance, right? It's a chemical compound called octane. C8H18. Eight carbon atoms linked together, i.e a hydrocarbon.

That carbon has to go somewhere when it's broken apart by the combustion process. Either accumulate in the engine, or out the exhaust; usually a little of both.

In a properly functioning engine(no issues) that carbon leaves the tailpipe mostly as carbon dioxide.
 

LibertyTC

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I run non ethanol chevron 94 and take the jeep out for hwy drives weekly now.
I also run FULL synthetic engine oils. Mobil1 extended performance is full syn, I use Penzoil Platinum, which is also good full syn.
BTW I've concluded all the 3.7's have a slight engine shake at idle cause they are an oddfire V6. Interesting read: LOST JEEPS • View topic - why do 3.7L's have a rough idle?
Have you ever replaced the PCV valve? Link:http://www.jeepkj.com/forum/f202/how-replace-pcv-valve-some-2007-up-jeep-liberty-57837/
& if misfires continue, check the fuel psi & consider a new Mopar injector.
 

K9JEEP

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I run non ethanol chevron 94 and take the jeep out for hwy drives weekly now.
I also run FULL synthetic engine oils. Mobil1 extended performance is full syn, I use Penzoil Platinum, which is also good full syn.
BTW I've concluded all the 3.7's have a slight engine shake at idle cause they are an oddfire V6. Interesting read: LOST JEEPS • View topic - why do 3.7L's have a rough idle?
Have you ever replaced the PCV valve? Link:http://www.jeepkj.com/forum/f202/how-replace-pcv-valve-some-2007-up-jeep-liberty-57837/
& if misfires continue, check the fuel psi & consider a new Mopar injector.
I am very familiar with carbon issues and what not being that my GTI is direct injection and suffers from carbon build up on the intake valves. The car requires 91 and I often Italian Tune it which is keeping the RPM's above 4k for 25 minutes or so, it's been said that frequent hard drives across the powerband will help with the build up but won't prevent it. I have that car on a custom pro tune and drive the hell out of it and have not noticed any carbon related issues at 39k miles, I also upgraded to Audi R8 coil packs to help keep that spark hot. This is the benefit of buying a car new, I know everything that has been done to the car.

As for the Jeep, I have not replaced to PCV, I did change the oil with Mobil 1 even though the oil had been changed but at a cheap Lube place. I still suspect water in the fuel from sitting for so long but that would not explain why I have gotten P0304 multiple times. I get P0300 every time but it does choose a specific cylinder as well most of the time. I added Seafoam to the gas yesterday to see if that helps. I should be filling up with fresh gas today and will add more.

I spoke with a Jeep service advisor today and the first thing he said was it sounds like bad gas because it's a random misfire. He said he would remove the tank and drain the gas a clean the full system first.

I'd also like to get that number 4 injector out and see what it looks like. Should I even bother with Seafoam in the throttle body?

I do realize the engine is naturally shaky, and I only get the CEL sometimes so I am not sure if the shake is normal or is worse by this issue.



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K9JEEP

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Update:
Compression came back good in all cylinders.
Injector seals were gunked up so I put a new injector in #4. Hopefully this will solve the issue.
The mechanic has had an 02 before and when I told him my problems he said it's probably the valve issue. But after testing everything we ruled out a lot and went with the Intejctor, the live readings of the injectors were good but he thought the spray pattern might not be correct with the head and seal dirty. The CEL came on right as I was waiting for him to look at it so he was able to do some live readings as it was on. I don't think he could actually view the miss though.
The shake is still there as that seems to be normal, I am not feeling much of a hesitation or struggle, just the shake.

As for fixing his valve issue. He said the machine shop he uses actually puts 5 or 6 punches where the valve seats and it completely stops it from ever falling or something of that nature. I will ask him more about that but he knew the exact issue and how to fix that, this is why I worked with him and not the first shop which is a little cleaner but didn't know jack about this issue.
BTW he quoted me as friend $1200 to fix the valve issue if it is that.

If the miss continues the next step is a leak down test.




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J33Pfan

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IMO; if you want to know if that injector is really bad, have it bench checked this way you know if that was really the problem. I send out all my fuel injectors to this guy. He tests them before & after then cleans/ rebuilds them. you get a complete report. Know if its the real problem.

ULTRASONIC FUEL INJECTOR CLEANING SERVICE | eBay
 

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