Rough idle/miss

Jackkep · Feb 18, 2018

Hi guys, I bought my 2002 Jeep Liberty in July with 150k on it. I'm now at 172k and I'm finally fed up with the slight miss I have at idle. I have changed the plugs, swapped out coils with OEM ones from a junkyard (I found a Libby that recently had a coil job before getting totalled), cleaned the IAC, and I swapped out the PCV valve when I did the plugs and coils. I've ran a couple bottles of Techron through which definitely helped a little and improved MPG and I'd like to say I also noticed a more aggressive acceleration as well. Before this car I only owned inline 4s so am I just crazy and all I'm noticing is the V6s inherent roughness? When I'm driving and come to a stop I idle perfectly for maybe 10-80 seconds and then I can start a feel a slight miss. Sometimes it's very noticeable and almost violent from a cold start. I used my scan tool to verify that the throttle is at a constant % when idling and it is (about 13.7%).

Am I crazy or is there something I'm missing?

Jackkep · Feb 18, 2018

I should add I do have a CEL. It's throwing a code for a "small" EVAP leak which I would've addressed first but it appeared well after I noticed the rough idle. I'm still trying to address that and find the leak. Maybe that is contributing?

ltd02 · Feb 18, 2018

Hate to say it but this may be as good as it gets. I think this is a common concern with newer KJ owners. If there is no misfire code then you may just be experiencing the joys of the 3.7L Powertech. They just do this. Both my 02 and 05 did/do it and could never solve it. I can't even tell my 98 Ranger with the 4.0L OHV and 171k is running at idle.

I'd definitely fix the evap leak. Maybe it'll help a bit but probably not.

Jackkep · Feb 18, 2018

ltd02 said:
Hate to say it but this may be as good as it gets. I think this is a common concern with newer KJ owners. If there is no misfire code then you may just be experiencing the joys of the 3.7L Powertech. They just do this. Both my 02 and 05 did/do it and could never solve it. I can't even tell my 98 Ranger with the 4.0L OHV and 171k is running at idle.

I'd definitely fix the evap leak. Maybe it'll help a bit but probably not.

Yeah I know it's not the smoothest engine on earth. I might try and track down another Liberty I can drive around and compare. It's just driving me crazy. Thanks

ltd02 · Feb 18, 2018

Not sure what plugs you're running but using the factory spec'd copper cores helped mine a little. I use the NGKs. I ran plats for a while and noticed a smoother idle when switched back to the coppers.

Jackkep · Feb 18, 2018

ltd02 said:
Not sure what plugs you're running but using the factory spec'd copper cores helped mine a little. I use the NGKs. I ran plats for a while and noticed a smoother idle when switched back to the coppers.

I used Autolite Double platinums. I tried OEM but I did not see a difference so I went with Autolites because of longevity. Plus I'm pretty sure the Autolites are copper core but platinum tip so kind of the best of both worlds. I triple checked my gaps to make sure they were in spec.

ltd02 · Feb 18, 2018

I ran the Bosch +4s for about 50k and went back to the NGKs. It did help. The 25k interval isn't too bad and the plugs are pretty cheap. Only takes me about 30 minutes to change all 6 anymore.

Jackkep · Feb 18, 2018

ltd02 said:
I ran the Bosch +4s for about 50k and went back to the NGKs. It did help. The 25k interval isn't too bad and the plugs are pretty cheap. Only takes me about 30 minutes to change all 6 anymore.

Alright if nothing else fixes the idle issue I'll swap back to OEM. If not I'll swap back at the next plug change. Thanks!

HoosierJeeper · Feb 18, 2018

It's an odd fire V6 so it's inherently unbalanced. Mine feels pretty smooth though. Dumb test but if you leave the driver's door open with it running, does the door shake? There was a member on here where his ran rough and I think it was the coil packs. OEM only. His door shook and in my head I kinda made that the normal line. Feels a little rough but door is steady = normal, door shakes = not normal.

Jackkep · Feb 18, 2018

HoosierJeeper said:
It's an odd fire V6 so it's inherently unbalanced. Mine feels pretty smooth though. Dumb test but if you leave the driver's door open with it running, does the door shake? There was a member on here where his ran rough and I think it was the coil packs. OEM only. His door shook and in my head I kinda made that the normal line. Feels a little rough but door is steady = normal, door shakes = not normal.

Alright I'll try that and report back. It doesn't just feel shaky. It runs normally (still unbalanced as ****) and then I can feel it jerk (miss) slightly and not with any sort of rhythm

LibertyTC · Feb 19, 2018

Wow this whole thread is like someone has read my experience/posts LOL..
What was the exact small EVAP code #? Gas cap? address the proper code..
Ya slight shake it's a 3.7 jeep thing.
Note with a proper scanner like a Snap On ultra, you can see the misfire count and on what cylinders.
Mine had hickups/ drop outs found especially around 16-1700 rpm with misfires showing & this was caused by damage to the backside of the TPS sensor, where plastic was carved out, by the throttle pin moving back & forth.
Make sure your battery terminals are clean as a whistle/ no corrosion & tight.
When it is cold outside it can shake worse, until it warms up.
Try running a good synthetic engine oil like Pennzoil platinum, and find a bottle of LubeGard bio-engine treatment, and take the KJ for a good hwy run with even more techron concentrate in the tank & see how it runs then.
In winter I also add STP all season water remover as ethanol fuel likes to absorb moisture.
I also carry a fuel stabilizer by strarbrite (star tron) and that helps if ya got stale fuel. High octane can also make it run better then.
Mine runs better now..but it is not the brightest engine on the block as it is an odd ball/ odd fire!

HerronScott · Feb 19, 2018

Jackkep said:
Hi guys, I bought my 2002 Jeep Liberty in July with 150k on it. I'm now at 172k and I'm finally fed up with the slight miss I have at idle.

Before this car I only owned inline 4s so am I just crazy and all I'm noticing is the V6s inherent roughness? When I'm driving and come to a stop I idle perfectly for maybe 10-80 seconds and then I can start a feel a slight miss. Sometimes it's very noticeable and almost violent from a cold start. I used my scan tool to verify that the throttle is at a constant % when idling and it is (about 13.7%).

ltd02 said:
Hate to say it but this may be as good as it gets. I think this is a common concern with newer KJ owners. If there is no misfire code then you may just be experiencing the joys of the 3.7L Powertech. They just do this. Both my 02 and 05 did/do it and could never solve it. I can't even tell my 98 Ranger with the 4.0L OHV and 171k is running at idle.

We have a 2002 with about 166,000 miles on it and it seems to idle pretty smoothly considering it seems like a very low idle speed (600rpm) compared to what I'm use to. My old 2004 Mazda 6s which had a Ford 3.0l V6 did seem to idle perhaps a bit smoother but that also idled a little higher at 750rpm.

I will say that I do recall seeing just a slight variance in the idle some times before we had the head and head gasket work done (before the issue that necessitated the work), but since then it's rock solid.

Scott

Jackkep · Feb 19, 2018

HerronScott said:
We have a 2002 with about 166,000 miles on it and it seems to idle pretty smoothly considering it seems like a very low idle speed (600rpm) compared to what I'm use to. My old 2004 Mazda 6s which had a Ford 3.0l V6 did seem to idle perhaps a bit smoother but that also idled a little higher at 750rpm.

I will say that I do recall seeing just a slight variance in the idle some times before we had the head and head gasket work done (before the issue that necessitated the work), but since then it's rock solid.

Scott

What prompted all the engine repairs?

HerronScott · Feb 19, 2018

Jackkep said:
What prompted all the engine repairs?

The usual, we had an overheating issue during our vacation drive to Charleston, SC during the summer. Didn't seem to impact it at the time but about 7 months later we had a bad miss and antifreeze in one of the cylinders (white smoke in the exhaust).

I had had to add a small amount of antifreeze a couple of times before the trip so I'm wondering if there may have been a pre-existing condition (the radiator was new when we bought it at 153,000 miles).

Scott

Jackkep · Feb 19, 2018

LibertyTC said:
Wow this whole thread is like someone has read my experience/posts LOL..
What was the exact small EVAP code #? Gas cap? address the proper code..
Ya slight shake it's a 3.7 jeep thing.
Note with a proper scanner like a Snap On ultra, you can see the misfire count and on what cylinders.
Mine had hickups/ drop outs found especially around 16-1700 rpm with misfires showing & this was caused by damage to the backside of the TPS sensor, where plastic was carved out, by the throttle pin moving back & forth.
Make sure your battery terminals are clean as a whistle/ no corrosion & tight.
When it is cold outside it can shake worse, until it warms up.
Try running a good synthetic engine oil like Pennzoil platinum, and find a bottle of LubeGard bio-engine treatment, and take the KJ for a good hwy run with even more techron concentrate in the tank & see how it runs then.
In winter I also add STP all season water remover as ethanol fuel likes to absorb moisture.
I also carry a fuel stabilizer by strarbrite (star tron) and that helps if ya got stale fuel. High octane can also make it run better then.
Mine runs better now..but it is not the brightest engine on the block as it is an odd ball/ odd fire!

The code was P0442. I've already tried a couple different gas caps. My miss seems to exclusively be at idle, I'm going to borrow my friend's Snap-on tool to check the mode 6 data

Vals4x4 · Feb 20, 2018

i noticed that whenever my 2002 had a CEL it ran a lil rough at idle until I cleared all codes.
the weather in NYC is above 30degs and everything is so much better. No codes no abnormal vibrations.
These Libertys are listed as a Truck for a reason

J33Pfan · Feb 20, 2018

Vals4x4 said:
i noticed that whenever my 2002 had a CEL it ran a lil rough at idle until I cleared all codes.
the weather in NYC is above 30degs and everything is so much better. No codes no abnormal vibrations.
These Libertys are listed as a Truck for a reason

oh yea we got some good weather in NYC! the Liberty LOVES this weather!

LibertyTC · Feb 21, 2018

Even tho mine is in top shape, it sat for only 2 days in below freezing temps & wow did it complain when I stated it up this AM at idle!
Had a club across the steering wheel, the club was rattling bad at idle. Bad ole engine shake, but no codes set.
F/That...Up went the rpm's to 1500 rpm for 4 minutes, that shut it up.
I would like to see the oil pressure in these conditions !
Good ole 3.7's....
61154[/ATTACH]"]

You must be registered for see images attach

k99jk99j · Feb 22, 2018

It's a 90 degree v-6, that was hatched from the 4.7l. it is normal if you have no miss fire! I have a manual transmission and its really bad. It's seems on the automatics it's more smooth since the torque converter masks the shake!

rizob · Feb 25, 2018

Mine has the same problem. I've been trying to figure it out for a few years now. Did all the same things you did and no change. Mine runs perfect when it's moving. It just idles bad. Same as yours when it's cold it's worse. Sometimes it's pretty bad and then sometimes not bad at all. I noticed if I have the AC or defrost on it's a lot worse. I wish there was a fix because I want t lift mine but afraid something is wrong with the engine.

Rough idle/miss

New Member

New Member

Comfortably numb

New Member

Comfortably numb

New Member

Comfortably numb

New Member

Gold Supporter/Admin

New Member

Well-Known Member

Full Access Member

New Member

Full Access Member

New Member

New Member

Full Access Member

Well-Known Member

Attachments

Full Access Member

New Member

Similar threads