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OT, Jeep Liberty Misfire Problem
Posted by: moomba32 ()
Date: April 10, 2018 04:57AM

It's a 2004 Jeep Liberty with 3.7 V6. This problem started within 60 seconds of filling the tank so the instant thought is bad gas. After a couple days of driving it I have a good feel for the symptoms. It has P0300 code which is random misfire. The spark plugs were original with 189,000 miles so swapped then, didn't expect it to fix it but it was time. It idles fine, the misfire occurs under 2000 RPM and with light or no acceleration. If you accelerate hard up to 75 you'd not see a problem because it stays above that 2000 mark. Cruising at 1500 it will misfire bad, as soon as you lift the pedal it clears up, drop the gear to increase RPM past 2000 RPM and it clears. Any ideas on what it is?

Don Marlowe
66 Monza 2Dr 140/pg
64 Spyder convertible now, 110/pg
Eutawville SC

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Re: OT, Jeep Liberty Misfire Problem
Posted by: 64turbo ()
Date: April 10, 2018 06:34AM

Just had a similar problem with my daughter's 2010 Mazda 3. It started running rough shortly after filling the tank. Then started throwing random misfire codes.

It did indeed turn out to be a tank of bad gas.I ran the car around town to burn off as much as possible and then filled it. It has been fine since.

Ron Manwaring
CT Corsa

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Re: OT, Jeep Liberty Misfire Problem
Posted by: Phil Dally ()
Date: April 10, 2018 07:04AM

Is there a fuel filter?

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Re: OT, Jeep Liberty Misfire Problem
Posted by: moomba32 ()
Date: April 10, 2018 07:05AM

I've used about half the gas so far, thinking about putting a can of Seafoam in it when it gets to about a quarter tank.

Don Marlowe
66 Monza 2Dr 140/pg
64 Spyder convertible now, 110/pg
Eutawville SC

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Re: OT, Jeep Liberty Misfire Problem
Posted by: glivorsi ()
Date: April 10, 2018 07:30AM

My ex had an '02 Ford Escape V6 that had a misfire under load. It had the exact same issue you describe where it would misfire under load at highway speeds and then would run okay when I took it out of overdrive. It did throw a code for misfire, but for a specific cylinder. It turned out to be a crack in the resin on one of the ignition coils, a known very common problem on Ford Duratechs. The problem was more pronounced during rainy or humid weather. Has your weather changed with the new tank of gas?

Greg in Wildwood, MO (part of the St. Louis urban sprawl)

1965 Monza Vert 110PG, Crocus Yellow with black interior and top

2014 Honda Accord V6 (DD)
2017 Honda Pilot (wifemobile)
2012 Chevy Sonic 1.8L (kid's car)
1997 Honda CBR1100XX
2006 Mazdaspeed 6 (no longer own)

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Re: OT, Jeep Liberty Misfire Problem
Posted by: moomba32 ()
Date: April 10, 2018 08:30AM

As far as I can tell there's no filter but it runs fine under heavy acceleration and anything over 2000 RPM is good ran 75 MPH this morning without a stumble so I expect it's getting fuel.

Don Marlowe
66 Monza 2Dr 140/pg
64 Spyder convertible now, 110/pg
Eutawville SC

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Re: OT, Jeep Liberty Misfire Problem
Posted by: gnvair ()
Date: April 10, 2018 09:08AM

Most Chrysler products since the mid 90's do not have a serviceable (or easily serviceable) fuel filter.
Odd that the misfire started after the fill up. Could be coincidental.
Typically misfires are obviously coils or injectors (not common failure of the Jeeps). Another thing that does happen is the valve seats get loose on the 3.7's and will cause misfires. If you check ignition and fuel and it is neither I would start looking into the seat issue. If you talk to guys in the field at Chrysler/Dodge/Jeep dealers you will find it is quite common on the 3.7/4.7 and 5.7 Hemi.

Lee J

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Re: OT, Jeep Liberty Misfire Problem
Posted by: Ratt643 ()
Date: April 10, 2018 10:00AM

What brand of spark plugs did you putin? Also, could be a throttle position sensor, bad spark plug wire or coil pack...
May just be a coincidence that it happened when you filled up the tank.


1964 Monza Coupe

Maryville, TN
U.S. 129 The"Tail Of The Dragon"

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Re: OT, Jeep Liberty Misfire Problem
Posted by: moomba32 ()
Date: April 10, 2018 10:53AM

Plugs are same as originally there except not wore out. It's coded random so it's not just one cylinder, it has different code if it were only one cylinder such as p0302 for misfire on 2 so doubtful it's valve or coil. I'm leaning towards vacuum leak, have looked some but nothing obvious. It has to be something messing with the air fuel mixture between idle and 2000 RPM. At idle it opens a separate air valve for idle air. Seems like a vacuum leak would mess up the idle though and it idles fine.

Don Marlowe
66 Monza 2Dr 140/pg
64 Spyder convertible now, 110/pg
Eutawville SC

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Re: OT, Jeep Liberty Misfire Problem
Posted by: moomba32 ()
Date: April 10, 2018 10:56AM

The TPS has merit, perhaps it's not seeing the throttle open until it moves further but it the only thing that seems to make a difference is RPM. Crank triggering?

Don Marlowe
66 Monza 2Dr 140/pg
64 Spyder convertible now, 110/pg
Eutawville SC

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Re: OT, Jeep Liberty Misfire Problem
Posted by: 64turbo ()
Date: April 10, 2018 11:46AM

Our Mazda 3 would idle and rev all day long in the driveway without throwing a code. We would get the code only when driving. The Mazda "experts" couldn't figure it out finally telling me the problem was the low compression of 155 in all cylinders even after mentioning the possibility of bad gas.

Ron Manwaring
CT Corsa

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Re: OT, Jeep Liberty Misfire Problem
Posted by: curt ()
Date: April 11, 2018 11:57AM

Would 189,000 miles on the spark plugs set up a situation where the plugs have "burned" so much that they slowly effect the coil(s)?

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Re: OT, Jeep Liberty Misfire Problem
Posted by: moomba32 ()
Date: April 11, 2018 04:43PM

It's on another tank of gas now, really no change so it's not looking like bad gas. It is really isolated to the RPM range from 1400-2200, anything below or above that is fine and it's ok in that range with a very light pedal. I have a Throttle Position Sensor I can put on it, doubt that's it but I swapped it out a while back when it had a different problem. The Crank Position Sensor crossed my mind with it being so tied to RPM more so than anything else.
I am learning to drive it, below 60 I turn off OD and the RPMs stay up in the happy zone, above that and it's OK with OD on. It doesn't lack power, pushed right up to 85 passing a truck today.

Don Marlowe
66 Monza 2Dr 140/pg
64 Spyder convertible now, 110/pg
Eutawville SC

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Re: OT, Jeep Liberty Misfire Problem
Posted by: flamingchariots ()
Date: April 12, 2018 04:41PM

I had a Subaru with those symptoms. Seemed it was something like fuel evaporative canister filter or something like that.
It would stumble like crazy ONLY when filled up. I had to feather and floor the gas pedal to clear it.

This may not have anything to do with yours. I sold the Subaru...

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Re: OT, Jeep Liberty Misfire Problem
Posted by: glivorsi ()
Date: April 13, 2018 06:09AM

Have you tried cleaning out the throttle body? Even with fuel injection they get a little dirty over time. There may be an idle passage that's a little gunked up.

You also may want to clean your EGR valve, although they typically throw a code for those. They get dirty and will either stick or leak through. They can usually be cleaned with carb cleaner and a fine wire brush.

Both of these are kind of shots in the dark, but with that high of mileage they are probably getting pretty dirty. I'm not familiar with this engine so I have no idea how much work is involved. They were super easy on my Cavalier and a nightmare on my Mazda.

Greg in Wildwood, MO (part of the St. Louis urban sprawl)

1965 Monza Vert 110PG, Crocus Yellow with black interior and top

2014 Honda Accord V6 (DD)
2017 Honda Pilot (wifemobile)
2012 Chevy Sonic 1.8L (kid's car)
1997 Honda CBR1100XX
2006 Mazdaspeed 6 (no longer own)

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Re: OT, Jeep Liberty Misfire Problem
Posted by: chris ()
Date: April 13, 2018 11:03AM

I'm just going to add this, but DIS ignition coils have done the same thing to me. My Pontiac started bucking and not wanting to stay running and gave the PO300 code. I initially replaced the coil packs with used ones. The issue was not much better after changing until I replaced the coil packs with new ones and problem solved! It turns out that the GM coil packs are notorious for failing like that but I'm not sure if Jeep has the same reputation.

'65 Monza 4 door
4 speed
110hp
Gardner, KS

Heart of America Corvair Owners Association

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Re: OT, Jeep Liberty Misfire Problem
Posted by: moomba32 ()
Date: April 13, 2018 06:24PM

Hopefully I can give it some time this weekend. Thanks for all the input.

Don Marlowe
66 Monza 2Dr 140/pg
64 Spyder convertible now, 110/pg
Eutawville SC

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Re: OT, Jeep Liberty Misfire Problem
Posted by: 4carbcorvair ()
Date: April 14, 2018 10:52AM

ASD relay?

--------------------------------
Ronnie
Southern Maine.
www.dirigocorvairs.net
66 Corsa Convertible, 140, 4sp.
65 Monza Convertible, 110, PG.




It doesn't leak, it's marking it's territory.

A mirror is a reflection of the miles travelled.

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Re: OT, Jeep Liberty Misfire Problem
Posted by: moomba32 ()
Date: April 14, 2018 04:35PM

ASD relay?


I saw that on the jeep forum, I looked briefly and it looks like the same relay as the one beside it so was thinking I'll swap them and see if anything changes.

Don Marlowe
66 Monza 2Dr 140/pg
64 Spyder convertible now, 110/pg
Eutawville SC

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Re: OT, Jeep Liberty Misfire Problem
Posted by: streblerm ()
Date: April 15, 2018 04:36AM

You might check out the MAF (mass air flow sensor) They make a special cleaner for them but I have used brake cleaner successfully. They are usually two little heated wires shrouded in a small bulb exposed to airflow in the air intake. If they are dirty they tell the computer that less air is getting to the engine which cuts the fuel trim as well. Eventually the o2 sensor takes over and evens out the fuel mix.

If the wires in the MAF aren’t bright and shiny then it won’t read correctly. Pull the sensor, spray it and wait a few seconds then spray again.

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