Rough Idle After Warm-up - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > TJ Jeep Wrangler Forum > TJ Tech Forum

Join Wrangler Forum Today


Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 01-11-2014, 04:22 PM   #1
Jeeper
 
Join Date: Apr 2013
Location: Connecticut
Posts: 168
Rough Idle After Warm-up

Hey Everyone,

First post in a while(Jeeps been running good!) Recently though, my '03 wrangler with a 4.0L has been idling rough, specifically after it comes up to temp. So rough that it seems like it wants to stall, but never does. It just "lobes" between 600 & 700 RPM, and then goes down to about 450 or so. Also, this only happens when I come to a complete stop. I could have it in neutral and be rolling and the engine idles fine. The second I come to a complete stop though it starts to drag and seems like it wants to die. It also has a bit of hesitation under initial acceleration. I have no CEL and I'm a little perplexed. I do have a squealing noise coming from the drive belt, could be a bad pulley.

Within the past year I've changed plugs, plug boots, fuel pump, both upstream O2 sensors, and put a new cat-back exhaust on. I also cleaned the throttle body and IAC. Tomorrow I'm changing my thermostat, thermostat housing, and upper radiator hose because of a small leak in that area. Not sure if that has anything to do with it. Any ideas/input would be appreciated.

__________________
2003 Jeep Wrangler X 4.0L ~ 107,000 miles
apannone is offline   Quote Quick Reply
Old 01-11-2014, 04:32 PM   #2
Jeeper
 
Pittsburghwrangler's Avatar
 
Join Date: Jun 2013
Location: Pittsburgh
Posts: 831
try cleaning your MAFS

Pittsburghwrangler is offline   Quote Quick Reply
Old 01-11-2014, 04:40 PM   #3
Jeeper
 
Join Date: Apr 2013
Location: Connecticut
Posts: 168
I believe my jeep has a MAP sensor rather than a MAFS, but I will clean it tomorrow. Thanks!
__________________
2003 Jeep Wrangler X 4.0L ~ 107,000 miles
apannone is offline   Quote Quick Reply
Old 01-11-2014, 05:01 PM   #4
Jeeper
 
Pittsburghwrangler's Avatar
 
Join Date: Jun 2013
Location: Pittsburgh
Posts: 831
ya you're right. sounds like you're pretty knowledgeable from the original post but ill say this anyway incase you or someone else didn't know: just make sure when you have the sensor pulled you do not touch the actual sensor as it will probably never work again
Pittsburghwrangler is offline   Quote Quick Reply
Old 01-17-2014, 12:50 PM   #5
Jeeper
 
Join Date: Apr 2013
Location: Connecticut
Posts: 168
I've still got a pretty rough idle. Is it worth flashing the pcm? What other steps could I take to diagnose it? Could it be a timing issue? I'm about ready to take it somewhere.

Ps the tstat and housing install went prefect. No more leak.
__________________
2003 Jeep Wrangler X 4.0L ~ 107,000 miles
apannone is offline   Quote Quick Reply
Old 01-17-2014, 01:11 PM   #6
Jeeper
 
Majnoon's Avatar
 
Join Date: Apr 2013
Location: Springfield Missouri
Posts: 2,866
I think it's a sensor somewhere. It runs off preset factory settings until it gets to temp. Then switches to info from sensors to run. I don't know a ton about this. It may apply to all sensors or a select few. It would make perfect since to cause your problem though. Maybe someone more knowing will see this and chime in. Good luck.
Majnoon is offline   Quote Quick Reply
Old 01-17-2014, 01:20 PM   #7
Jeeper
 
Pittsburghwrangler's Avatar
 
Join Date: Jun 2013
Location: Pittsburgh
Posts: 831
Quote:
Originally Posted by Majnoon View Post
I think it's a sensor somewhere. It runs off preset factory settings until it gets to temp. Then switches to info from sensors to run. I don't know a ton about this. It may apply to all sensors or a select few. It would make perfect since to cause your problem though. Maybe someone more knowing will see this and chime in. Good luck.
This was the reason i recommended cleaning the MAFS (or MAP sensor) earlier im not sure what other sensors this may apply to maybe o2?
__________________
1995 YJ Rio Grande 2.5l I4 Auto, random cheap mods, saving money for OME 2.5" lift
Pittsburghwrangler is offline   Quote Quick Reply
Old 01-17-2014, 01:27 PM   #8
Jeeper
 
Join Date: Apr 2013
Location: Connecticut
Posts: 168
I'll check the MAP again. Last week when I plugged my reader in I did have a pending code for one of the o2 sensors, but it never triggered a CEL. And the pending code hasn't returned since. That's why I thought flashing the pcm might help?
__________________
2003 Jeep Wrangler X 4.0L ~ 107,000 miles
apannone is offline   Quote Quick Reply
Old 01-17-2014, 06:39 PM   #9
Jeeper
 
Pittsburghwrangler's Avatar
 
Join Date: Jun 2013
Location: Pittsburgh
Posts: 831
Well if you have the resources to reflash yourself i dont see why not it can only help but if not why pay a dealer until you have ruled out all other options... I would also check your TPS, although if this was a problem there would probably be other symptoms while you drive. At this point i am going off of knowledge from working on my '07 xterra since my YJ has a little less technology but, maybe try disconnecting your battery for awhile (not sure how long i think i waited an hour?) and then reconnecting it so that your ECM will reset, i fixed an acceleration lag with this trick
__________________
1995 YJ Rio Grande 2.5l I4 Auto, random cheap mods, saving money for OME 2.5" lift
Pittsburghwrangler is offline   Quote Quick Reply
Old 01-17-2014, 06:55 PM   #10
Jeeper
 
Join Date: Apr 2013
Location: Connecticut
Posts: 168
I do have a hesitation while accelerating so it could be the tps. And the pcm flash is pretty simple so I'll do that first thing in the morning.
__________________
2003 Jeep Wrangler X 4.0L ~ 107,000 miles
apannone is offline   Quote Quick Reply
Old 01-17-2014, 11:47 PM   #11
Jeeper
 
Majnoon's Avatar
 
Join Date: Apr 2013
Location: Springfield Missouri
Posts: 2,866
Bump. Lots of folks on now. Any ideas?
Majnoon is offline   Quote Quick Reply
Old 01-18-2014, 11:22 AM   #12
Jeeper
 
Join Date: Apr 2013
Location: Connecticut
Posts: 168
Quote:
Originally Posted by Majnoon View Post
Bump. Lots of folks on now. Any ideas?
Guess not. Thanks for trying tho
__________________
2003 Jeep Wrangler X 4.0L ~ 107,000 miles
apannone is offline   Quote Quick Reply
Old 01-18-2014, 05:34 PM   #13
Jeeper
 
Pittsburghwrangler's Avatar
 
Join Date: Jun 2013
Location: Pittsburgh
Posts: 831
The flash didnt help?
__________________
1995 YJ Rio Grande 2.5l I4 Auto, random cheap mods, saving money for OME 2.5" lift
Pittsburghwrangler is offline   Quote Quick Reply
Old 01-19-2014, 04:51 PM   #14
Jeeper
 
Join Date: Apr 2013
Location: Connecticut
Posts: 168
No, the flash didn't change anything. Still idling rough. Guess I'll have to start looking into sensors. I changed both upstream 02 sensors about 3 months ago. Should I start by changing the downstream sensors? Could the downstream sensors cause a rough idle? If not, what other sensors should I first check?
__________________
2003 Jeep Wrangler X 4.0L ~ 107,000 miles
apannone is offline   Quote Quick Reply
Old 01-19-2014, 05:05 PM   #15
Jeeper
 
Pittsburghwrangler's Avatar
 
Join Date: Jun 2013
Location: Pittsburgh
Posts: 831
It would be nice to hear from someone else about this but from my knowledge the downstream sensors are to check the catalytic converter not the air-fuel ratio so probably not... I would start by checking the upstream connections. Maybe even give the contacts a blast of contact cleaner... Other than this could the timing be off? Im about at the ends of my knowledge. Again it would be nice to hear from someone with more experience
__________________
1995 YJ Rio Grande 2.5l I4 Auto, random cheap mods, saving money for OME 2.5" lift
Pittsburghwrangler is offline   Quote Quick Reply
Old 01-19-2014, 06:11 PM   #16
Jeeper
 
Join Date: Apr 2013
Location: Connecticut
Posts: 168
Thanks for all the input Pitt. Anyone have suggestions on checking the timing? As I understand it, the timing being slightly off could cause what I'm describing.
__________________
2003 Jeep Wrangler X 4.0L ~ 107,000 miles
apannone is offline   Quote Quick Reply
Old 01-19-2014, 07:00 PM   #17
Jeeper
 
Majnoon's Avatar
 
Join Date: Apr 2013
Location: Springfield Missouri
Posts: 2,866
If timing was off wouldn't it be happening when cold as well? I think so. I could be wrong though never had the problem my self. I would think that would cause it to run rough all the time not just when it gets up to temp.
Majnoon is offline   Quote Quick Reply
Old 01-19-2014, 07:21 PM   #18
Jeeper
 
JimsJeep's Avatar
 
Join Date: Feb 2012
Location: Long Branch NJ
Posts: 1,137
The title of your thread leads me to believe that it may have something to do with a warmer engine where something could be expanding and permitting a vacuum leak.
__________________
2000 Wrangler Metallic Fern Green
1999 Wrangler Chili Pepper Red
1976 Triumph TR6 British Racing Green
JimsJeep is online now   Quote Quick Reply
Old 01-20-2014, 06:27 AM   #19
Jeeper
 
Join Date: Apr 2013
Location: Connecticut
Posts: 168
Quote:
Originally Posted by JimsJeep View Post
The title of your thread leads me to believe that it may have something to do with a warmer engine where something could be expanding and permitting a vacuum leak.
Alright. I've never had to check for a vacuum leak before. Any suggestions? Also do you happen to know the "normal" vacuum pressure in a tj? I've noticed the vacuum pressure drop off just as the engine idle get weak and stumbles. It goes from 19 in/Hg down to 17 in/Hg. Is that normal?
__________________
2003 Jeep Wrangler X 4.0L ~ 107,000 miles
apannone is offline   Quote Quick Reply
Old 01-20-2014, 09:46 AM   #20
Knows a couple things...

WF Supporting Member
 
Jerry Bransford's Avatar
 
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 30,866
Images: 2
My bet is you have a bad upstream 02 sensor, of which your 2003 has two of them.

The engine computer pays no attention to the 02 sensors during warm up but once the engine is warmed up, then it starts relying on the 02 sensors to provide the proper air/fuel mixture.
__________________
When you have a choice, buy American.

Jerry Bransford is online now   Quote Quick Reply
Old 01-20-2014, 10:11 AM   #21
Jeeper
 
Join Date: Apr 2013
Location: Connecticut
Posts: 168
Quote:
Originally Posted by Jerry Bransford View Post
My bet is you have a bad upstream 02 sensor, of which your 2003 has two of them.

The engine computer pays no attention to the 02 sensors during warm up but once the engine is warmed up, then it starts relying on the 02 sensors to provide the proper air/fuel mixture.
Thanks jerry! I replaced both upstream o2 sensors a few months back. I used ntk. How are they with replacing defective units? I bought them from rock auto.
__________________
2003 Jeep Wrangler X 4.0L ~ 107,000 miles
apannone is offline   Quote Quick Reply
Old 01-20-2014, 03:50 PM   #22
Jeeper
 
Join Date: Apr 2013
Location: Connecticut
Posts: 168
Also, is there a reason the issue is only seen at idle?
__________________
2003 Jeep Wrangler X 4.0L ~ 107,000 miles
apannone is offline   Quote Quick Reply
Old 01-23-2014, 09:33 AM   #23
Jeeper
 
Join Date: Apr 2013
Location: Connecticut
Posts: 168
Well I bought 2 new upstream sensors. Will throw them in and update you all.
__________________
2003 Jeep Wrangler X 4.0L ~ 107,000 miles
apannone is offline   Quote Quick Reply
Old 01-23-2014, 11:26 AM   #24
Jeeper
 
Majnoon's Avatar
 
Join Date: Apr 2013
Location: Springfield Missouri
Posts: 2,866
Quote:
Originally Posted by apannone View Post
Well I bought 2 new upstream sensors. Will throw them in and update you all.
Cool looking forward to seeing if it works!
Majnoon is offline   Quote Quick Reply
Old 01-23-2014, 11:33 AM   #25
Jeeper
 
Pittsburghwrangler's Avatar
 
Join Date: Jun 2013
Location: Pittsburgh
Posts: 831
Quote:
Originally Posted by Majnoon View Post

Cool looking forward to seeing if it works!
x2
__________________
1995 YJ Rio Grande 2.5l I4 Auto, random cheap mods, saving money for OME 2.5" lift
Pittsburghwrangler is offline   Quote Quick Reply
Old 01-26-2014, 09:37 AM   #26
Jeeper
 
Join Date: Apr 2013
Location: Connecticut
Posts: 168
See below for what the sensors I pulled out looked like. So far the Jeep seems to be running better but the idle is still weak.

Click image for larger version

Name:	ForumRunner_20140126_103431.jpg
Views:	49
Size:	63.0 KB
ID:	703777
__________________
2003 Jeep Wrangler X 4.0L ~ 107,000 miles
apannone is offline   Quote Quick Reply
Old 01-26-2014, 01:41 PM   #27
Jeeper
 
Pittsburghwrangler's Avatar
 
Join Date: Jun 2013
Location: Pittsburgh
Posts: 831
What exactly do you mean by weak?
__________________
1995 YJ Rio Grande 2.5l I4 Auto, random cheap mods, saving money for OME 2.5" lift
Pittsburghwrangler is offline   Quote Quick Reply
Old 01-26-2014, 01:44 PM   #28
Jeeper
 
Join Date: Apr 2013
Location: Connecticut
Posts: 168
It'll sit around 625-650 then drop to 500, then surge to 700. It does this over and over when warmed up and sitting at idle.
__________________
2003 Jeep Wrangler X 4.0L ~ 107,000 miles
apannone is offline   Quote Quick Reply
Old 01-26-2014, 01:44 PM   #29
Jeeper
 
Join Date: Apr 2013
Location: Connecticut
Posts: 168
Oh and I got those rpm numbers while using my reader.
__________________
2003 Jeep Wrangler X 4.0L ~ 107,000 miles
apannone is offline   Quote Quick Reply
Old 01-26-2014, 01:48 PM   #30
Jeeper
 
Rrampley's Avatar
 
Join Date: May 2012
Location: APPLE VALLEY CA
Posts: 2,627
Keeping an eye here as I have the same issue on my 98. Have real aces several sensors although at the moment I can't remember which ones. But mine doesn't happen all the time. It's intermittent. Some says it's amazing and others like yesterday, just seems she is tired. Lol

__________________

Rhonda Misfit 4WD Secretary
Loving life one jeep trip at a time.
Rrampley is offline   Quote Quick Reply
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Jeep Wrangler Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



logo carid shop wrangler parts carid fender flares custom wheels store avs deflectors at carid
» Rates
Get low rates on auto insurance in Canada!

» Network Links
»Jeep Parts
» Featured Product

All times are GMT -5. The time now is 04:15 PM.



Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, and Grand Cherokee are copyrighted and trademarked to Chrysler Motors LLC.
Wranglerforum.com is not in any way associated with the Chrysler Motors LLC