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Rough idle

Tiny
DLLRP
  • MEMBER
  • 2005 JEEP LIBERTY
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 36,000 MILES
I replaced my plugs on my 2005 Liberty for a rough idle at 36000 miles, I still have a rough idle with no error codes. Runs fine other than rough idle.
Friday, July 24th, 2009 AT 7:17 AM

26 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Have you checked closely for a vacuum leak?
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Wednesday, August 26th, 2009 AT 1:54 PM
Tiny
DLLRP
  • MEMBER
  • 2 POSTS
I checked all hoses and used a gauge that showed good vaccum with no deveation.
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Friday, August 28th, 2009 AT 3:54 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
When you replaced the plugs, were the plug boots replaced? Some coils come with new ones, some dont. Sometimes they will arc through the side of a bad plug boot causing a rough idle.
See the guide below on misfires

https://www.2carpros.com/articles/engine-misfires-or-runs-rough
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Saturday, August 29th, 2009 AT 12:04 AM
Tiny
KATT526
  • MEMBER
  • 2 POSTS
  • 2002 JEEP LIBERTY
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 11,000 MILES
I can feel the vehicle pulsating when stopped. Also when I am driving and let off the accelerator it slows down tremendously almost to a complete stop, this just recently started. It happens every time, does not matter about morning, evening, or temperature. I have never replaced the fuel filter, could this be causing my problem, or what are my options? Please help.
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Wednesday, October 10th, 2018 AT 4:47 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Has the check engine light come on?
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Wednesday, October 10th, 2018 AT 4:47 PM (Merged)
Tiny
KATT526
  • MEMBER
  • 2 POSTS
Thanks for replying. No check engine light on. It has been tuned up also. It feels like it is restricted when I accelerate.
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Wednesday, October 10th, 2018 AT 4:47 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
There are a couple things this could be caused by. First, I would like you to check the catalytic converter to make sure it is not plugged. That will cause a loss of power. Also, the fuel pump pressure should be checked. The fact that the light has not come on tells me that it is not sensor related or electrically related.

Here is a how to for checking fuel pump pressure:

https://www.2carpros.com/how_to/how_to_check_fuel_pressure.htm

You will need a fuel pressure gauge. Most parts stores will lend or rent them to you. Also, as far as the converter, with the engine running, see if it feels like there is enough pressure coming from the exhaust. Also, listen for any hissing or rattling sounds near the converter.

Let me know what you find.

Joe
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Wednesday, October 10th, 2018 AT 4:47 PM (Merged)
Tiny
MR. LIBERTY
  • MEMBER
  • 1 POST
  • 2002 JEEP LIBERTY
I have a 2002 Jeep Liberty 3.7L, 6 cyl, 4wd Auto. With 170,000 miles my Jeep is idling very rough at start up. If I let it run for 15-20 minutes, turn it off, then start it up again after waiting 30 secs, it usually runs smoothly and can last up to 30 miles. If I turn it off and let it sit for more than 30 minutes, it will start idling rough again and stall when I slow to a stop. I have a had a vacuum leak repaired, fuel injector replaced and all of them cleaned, one coil replaced, spark plug wire for 6th cylinder replaced, internal computer module replaced, right side oxygen sensors replaced, complete carbon flush and compression is good. Diagnostics tell me that the 6th cylinder is not firing as it should be. I am trying to find out what else could possibly cause the 6th cylinder to not be firing as it should.
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Wednesday, October 10th, 2018 AT 4:47 PM (Merged)
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
If you don't have a code for the temp sensor. Change it anyway!
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Wednesday, October 10th, 2018 AT 4:47 PM (Merged)
Tiny
WCARPENTER
  • MEMBER
  • 1 POST
  • 2003 JEEP LIBERTY
  • 200,000 MILES
Vehicle looses power going up hills. Rough start from complete stop until gas pedal is pushed half way down. Check engine light continuously flashes while idling or driving. Codes in computer are multiple misfires cylinders 1-6 all. Plus both downstream o2 sensors heated. I was told two answers. And the 3.7 is coil over plug on all 6 cylinders. Thank you. Bill.
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Wednesday, October 10th, 2018 AT 4:47 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
How long since plugs/coils?

I would also do a compression test.

From all these failures, I would look closely at wiring harness for damage

Roy
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Wednesday, October 10th, 2018 AT 4:48 PM (Merged)
Tiny
JIMSAUTO
  • MEMBER
  • 16 POSTS
  • 2002 JEEP LIBERTY
  • 203,000 MILES
Working on a 2002 Jeep Liberty. Doesn't have any codes coming up. I have already replaced the CPS, CKS, 2 coils, all 6 plugs and cleaned the TB and IAC. Issue has improved but not by much. It is smoking and smells of gas when running.
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Wednesday, October 10th, 2018 AT 4:48 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
First scan for codes and check fuel pressure including fuel pressure after shut down. Then check for a vacuum leak or hoses disconnected or holes in them
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Wednesday, October 10th, 2018 AT 4:48 PM (Merged)
Tiny
JIMSAUTO
  • MEMBER
  • 16 POSTS
I have already scanned and don't have any codes, also checked fuel pressure and vacuum hoses. One weird thing was while trying to figure this out had fuel injector on #2 disconnected from harness and coil and plug out on #1 and the engine smoothed out a lot.
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Wednesday, October 10th, 2018 AT 4:48 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
You cancelled the companion cylinder by doing that and it will run smoother.

Did you do a compression test?

Roy
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Wednesday, October 10th, 2018 AT 4:48 PM (Merged)
Tiny
JIMSAUTO
  • MEMBER
  • 16 POSTS
Haven't yet, does this one recommend operating temp for compression check or not(I don't have a book that covers the 3.7 V6)
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Wednesday, October 10th, 2018 AT 4:48 PM (Merged)
Tiny
JIMSAUTO
  • MEMBER
  • 16 POSTS
Also just talked to the customer and was told a compression check was done about 4 or 5 months ago and was fine then.
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Wednesday, October 10th, 2018 AT 4:48 PM (Merged)
Tiny
04LIBERTY
  • MEMBER
  • 1 POST
  • 2004 JEEP LIBERTY
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 110,000 MILES
Trying to figure out why I am getting such poor mileage and rough idle, have replaced all plugs and done fuel treatment and injector cleaning, and then had computer codes checked as well as compression, took out new plugs and still no gunk, any suggestions would be great help
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Wednesday, October 10th, 2018 AT 4:48 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
What I have found is many times a bad O2 sensor will cause the problem described. Has it been replaced?

Also, does the vehicle seem to have a normal amount of power?
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Wednesday, October 10th, 2018 AT 4:48 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Because of the miles also check cam or followeres for wear, maybe a lobe is rounded off and you get compression but valves aren't workin g right. That wold not show up on a compression check or fuel pressure regulator may be screwed up as well
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Wednesday, October 10th, 2018 AT 4:48 PM (Merged)

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