2004 Wrangler Rubicon rough idle - Jeep Wrangler Forum
Jeep Wrangler Forum

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

Join Wrangler Forum Today


Like Tree2Likes
  • 2 Post By Jerry Bransford
Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 12-09-2019, 11:35 AM
Thread Starter
  #1
Jeeper
 
Join Date: Jan 2011
Posts: 18
2004 Wrangler Rubicon rough idle

I have a TJ Rubicon, 4.0, 5 spd. w/148000 miles, that runs and drives great. The only problem is a rough idle. I have replaced motor mounts, checked for vacuum leaks, (none found) and now am looking at the TPS. Anyone have other ideas?

Thanks,


Rick

RDW704 is offline   Quote
Old 12-09-2019, 11:44 AM   #2
XBD
Jeeper
 
XBD's Avatar
 
Join Date: Oct 2017
Location: Tallahassee, FL
Posts: 1,217
Cleaning your throttle body and IAC sensor is a quick check.
Plugs look good and gapped correctly still?
Does it happen when the engine is cold? hot? both? worse for either?
o2 sensors?

__________________
Keep it simple stupid
Instagram: @dillydillybar
XBD is offline   Quote
Old 12-10-2019, 10:39 AM
Thread Starter
  #3
Jeeper
 
Join Date: Jan 2011
Posts: 18
The throttle body has been cleaned and a new IAC installed. The plugs are new and gapped correctly. The only idea I have is the TPS needs replaced. The rough idle occurs pretty much all the time. It is a little better on cold start up, but then comes right back when it is warm.

What do you think?
RDW704 is offline   Quote
Sponsored Links
Advertisement
 
Old 12-10-2019, 10:50 AM   #4
XBD
Jeeper
 
XBD's Avatar
 
Join Date: Oct 2017
Location: Tallahassee, FL
Posts: 1,217
Quote:
Originally Posted by RDW704 View Post
The throttle body has been cleaned and a new IAC installed. The plugs are new and gapped correctly. The only idea I have is the TPS needs replaced. The rough idle occurs pretty much all the time. It is a little better on cold start up, but then comes right back when it is warm.

What do you think?
Hmm. Mine was having issues, but only when it was really hot and I'd re-crank it (i.e. after I make a quick pitstop and shut off / restart my engine). Since yours happens when it's cold too I'm not very sure. Check all your vacuum lines? I've had a few crack over the years and was causing a higher rpm idle.
__________________
Keep it simple stupid
Instagram: @dillydillybar
XBD is offline   Quote
Old 12-10-2019, 11:13 AM   #5
Knows a couple things...

WF Supporting Member
 
Jerry Bransford's Avatar
 
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 48,566
Newer 4.0L engines like yours have a waste spark ignition system which makes them very fussy about what type of spark plugs it'll run well on without a rough idle or misfires. Single tipped platinum plugs like the Autolite AP985 or Champion 3034 will cause mysterious idle and/or misfire problems even though some guide books say they're correct. Same with Bosch which have limited heat ranges typically never run well in our Jeeps.

3 known good plugs include the Autolite APP985 and Champion 7412, both double tipped platinums good for 100k miles, and the 200k mile iridium tipped Autolite XP985.

A bad TPS can cause a bad idle too.
XBD and rubycube like this.
__________________
When you have a choice, buy American.
Jerry Bransford is offline   Quote
Old 12-11-2019, 11:51 AM   #6
BM3
Jeeper
 
BM3's Avatar
 
Join Date: Jan 2016
Location: Cedar Rapids, Ia.
Posts: 248
Quote:
Originally Posted by RDW704 View Post
The rough idle occurs pretty much all the time. It is a little better on cold start up, but then comes right back when it is warm.
What do you think?
I would think upstream O2 sensor since it gets worse once it is warmed up and goes into closed loop
BM3 is offline   Quote
Old 12-11-2019, 12:24 PM   #7
Jeeper
 
Caden_TJ's Avatar
 
Join Date: May 2017
Posts: 271
Quote:
Originally Posted by Jerry Bransford View Post
Newer 4.0L engines like yours have a waste spark ignition system which makes them very fussy about what type of spark plugs it'll run well on without a rough idle or misfires. Single tipped platinum plugs like the Autolite AP985 or Champion 3034 will cause mysterious idle and/or misfire problems even though some guide books say they're correct. Same with Bosch which have limited heat ranges typically never run well in our Jeeps.

3 known good plugs include the Autolite APP985 and Champion 7412, both double tipped platinums good for 100k miles, and the 200k mile iridium tipped Autolite XP985.

A bad TPS can cause a bad idle too.
I have a rough idel sometimes but its only for like 15-20 seconds and a few revs stops it. That is on my 2006 Rubi, will those plugs above work on my year? Also, do you think that could cause the issue?
Caden_TJ is offline   Quote
Old 12-11-2019, 04:00 PM   #8
Knows a couple things...

WF Supporting Member
 
Jerry Bransford's Avatar
 
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 48,566
Quote:
Originally Posted by Caden_TJ View Post
I have a rough idel sometimes but its only for like 15-20 seconds and a few revs stops it. That is on my 2006 Rubi, will those plugs above work on my year? Also, do you think that could cause the issue?
Yes those plugs are also totally appropriate for your 06. Other possibilities for a rough idle include a bad TPS, dirty IAC, or even a bad O2 sensor.
__________________
When you have a choice, buy American.
Jerry Bransford is offline   Quote
Old 12-19-2019, 11:41 AM
Thread Starter
  #9
Jeeper
 
Join Date: Jan 2011
Posts: 18
Ok. To date, I have replaced the plugs with the autolite App985 and properly gapped them. I have replaced the TPS, IAC, motor mounts and checked the entire Jeep for vacuum leaks. Still have the low/rough idle. It is fine on cold start up, but after warming up the idle speed drops. Someone said that it may be an O2 sensor. Would I not get a check engine light if the O2 were bad?

Any other thoughts?
RDW704 is offline   Quote
Old 12-19-2019, 12:22 PM   #10
BM3
Jeeper
 
BM3's Avatar
 
Join Date: Jan 2016
Location: Cedar Rapids, Ia.
Posts: 248
Quote:
Originally Posted by RDW704 View Post
Ok. To date, I have replaced the plugs with the autolite App985 and properly gapped them. I have replaced the TPS, IAC, motor mounts and checked the entire Jeep for vacuum leaks. Still have the low/rough idle. It is fine on cold start up, but after warming up the idle speed drops. Someone said that it may be an O2 sensor. Would I not get a check engine light if the O2 were bad?

Any other thoughts?
On my 98 I never did get a CEL, just the rough idle when it went into closed loop. Use NGK/NTK sensors

BM3 is offline   Quote
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not 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






All times are GMT -5. The time now is 01:56 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.1
User Alert System provided by Advanced User Tagging v3.1.0 (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.

Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, Gladiator, Mopar and Grand Cherokee are copyrighted and trademarked to FCA US LLC.
Wranglerforum.com is not in any way associated with FCA US LLC.