High Idle ONLY 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 08-20-2010, 07:17 PM   #1
Jeeper
 
chrisb0108's Avatar
 
Join Date: Mar 2010
Location: FL
Posts: 297
High Idle ONLY after warm up!!

I pretty positive I have a small crack in my exhaust manifold. After warm up and only after warm up the idle will sit consistantly at around 1800 rpms. It idles fine when cold, but starts increasing pretty quick after running for a few minutes. I was thinking that if my IAC is the problem that it would do it all the time and not only when the Jeep is at running temp. Figured if its the TPS that I would have a low idle. I've checked all my vacuum lines and haven't found any of them to show signs of wear or looseness. I'm just trying to get some advise before I go out and just start buying all kinds of parts.

Edit: I searched on this site, as well as quite a few others before posting this. I found a lot of talk about high idle when cold and low idles but nothing exactly like the problems I'm having.

__________________
'98 TJ 2.5L
chrisb0108 is offline   Quote Quick Reply
Old 08-21-2010, 11:57 AM   #2
Jeeper
 
chrisb0108's Avatar
 
Join Date: Mar 2010
Location: FL
Posts: 297
I just hit a *bump* in the road

__________________
'98 TJ 2.5L
chrisb0108 is offline   Quote Quick Reply
Old 08-31-2010, 01:40 AM   #3
Jeeper
 
chrisb0108's Avatar
 
Join Date: Mar 2010
Location: FL
Posts: 297
Just replaced the IAC and still idles high after warm up. The air charge sensor (screws into the top of the intake manifold) looks bent on the inside and was caked up with black oily crap when I unscrewed it and took it out. If that sensor isn't reading right would that cause the high idle ONLY after the Jeep is warmed up? Literally, the RPMs will slowly creep up as the Jeep warms up. It maxes out at around 1800 RPMs at idle after full warm up. Any advice at all?? I could go purchase a new TPS, MAP and Intake Temp Sensor and just go from there but those things aren't returnable after they've been installed already so I'm hoping to narrow this problem down before forking out $$ I don't have. Any help is greatly appreciated. Oh I also went over all the vacuum hoses and they all seem to be seated down pretty good.
__________________
'98 TJ 2.5L
chrisb0108 is offline   Quote Quick Reply
Old 08-31-2010, 02:36 AM   #4
Jeeper
 
chrisb0108's Avatar
 
Join Date: Mar 2010
Location: FL
Posts: 297
I have a small crack in my exhaust manifold but that wouldn't cause a vacuum leak or high idle after warm up would it?
__________________
'98 TJ 2.5L
chrisb0108 is offline   Quote Quick Reply
Old 08-31-2010, 03:39 AM   #5
Jeeper
 
M.r.G.5150's Avatar
 
Join Date: Aug 2010
Location: right now hawaii, soon washington state
Posts: 18
The first thing I would consider is that the EGR valve is not closing completely when it gets hot. So I would remove and thoroughly clean the deposits out of the EGR valve. After that, try manually opening and releasing the valve; it should close easily and completely every time. If it does not close consistently, the EGR valve should be replaced.

After having been driven that many miles, it is also likely that fit of the valve stems in the cylinder head valve guides has become loose. When that happens; air can be sucked in to the intake manifold through the valve guides. Loose valve guides will in that way cause the air fuel mixture to become diluted. Loose guides will also result in inconsistent valve sealing, which causes the cylinder compression to drop. And both of those things can create increased or unstable idle speeds.

There is one other possible cause for this problem: Today's gasolines contain chemicals which produce heavy carbon deposits on valve stems. This can prevent valves from closing consistently or completely. So it might be worthwhile to add a full bottle of Chevron Techron fuel injection and combustion chamber cleaner to the fuel tank just before filling it with fuel. This product often takes 50 to 75 miles of driving to do its work. But the results are better than other products of that type.

I tried all the things suggested and the problem persisted on my 91 Jeep Cherokee. I was about to give up on it and just beginning to really get used to driving that way.
I then notice about half the exhaust manifold bolts were loose and tightened them to the proper torque settings which somehow cured the high idle problem.
I have no idea how this could be connected, but it is something others can try if the problem cannot be resolved in the proper manner.



hey i found this on another forum it's a cherokee but i hope it helps good luck
__________________

we are all worms, but i do believe i am a glow worm
M.r.G.5150 is offline   Quote Quick Reply
Old 08-31-2010, 03:42 AM   #6
Jeeper
 
M.r.G.5150's Avatar
 
Join Date: Aug 2010
Location: right now hawaii, soon washington state
Posts: 18
oh btw the OP said they replaced the IAC also w/o effect
__________________

we are all worms, but i do believe i am a glow worm
M.r.G.5150 is offline   Quote Quick Reply
Old 08-31-2010, 10:01 AM   #7
Jeeper
 
chrisb0108's Avatar
 
Join Date: Mar 2010
Location: FL
Posts: 297
Thanks for the response....Any idea where the EGR valve can be found on my 98 2.5L?
__________________
'98 TJ 2.5L
chrisb0108 is offline   Quote Quick Reply
Old 08-31-2010, 04:15 PM   #8
Jeeper
 
chrisb0108's Avatar
 
Join Date: Mar 2010
Location: FL
Posts: 297
Quote:
Originally Posted by chrisb0108 View Post
Just replaced the IAC and still idles high after warm up. The air charge sensor (screws into the top of the intake manifold) looks bent on the inside and was caked up with black oily crap when I unscrewed it and took it out. If that sensor isn't reading right would that cause the high idle ONLY after the Jeep is warmed up? Literally, the RPMs will slowly creep up as the Jeep warms up. It maxes out at around 1800 RPMs at idle after full warm up. Any advice at all?? I could go purchase a new TPS, MAP and Intake Temp Sensor and just go from there but those things aren't returnable after they've been installed already so I'm hoping to narrow this problem down before forking out $$ I don't have. Any help is greatly appreciated. Oh I also went over all the vacuum hoses and they all seem to be seated down pretty good.
Quote:
Originally Posted by chrisb0108 View Post
I have a small crack in my exhaust manifold but that wouldn't cause a vacuum leak or high idle after warm up would it?
Quote:
Originally Posted by chrisb0108 View Post
Thanks for the response....Any idea where the EGR valve can be found on my 98 2.5L?
Bump for more advice...
__________________
'98 TJ 2.5L
chrisb0108 is offline   Quote Quick Reply
Old 08-31-2010, 06:33 PM   #9
Jeeper
 
chrisb0108's Avatar
 
Join Date: Mar 2010
Location: FL
Posts: 297
For search result purposes.....the high idle ended up being a result of loose manifold bolts. The far bolt near the firewall was so loose I could turn it with my finger and all but one of the other bolts were really loose. Idling at a nice and quiet 700 RPMs now!!!
__________________
'98 TJ 2.5L
chrisb0108 is offline   Quote Quick Reply
Old 08-31-2010, 11:17 PM   #10
Jeeper
 
M.r.G.5150's Avatar
 
Join Date: Aug 2010
Location: right now hawaii, soon washington state
Posts: 18
Quote:
Originally Posted by chrisb0108 View Post
For search result purposes.....the high idle ended up being a result of loose manifold bolts. The far bolt near the firewall was so loose I could turn it with my finger and all but one of the other bolts were really loose. Idling at a nice and quiet 700 RPMs now!!!
right on bro glad to see it

__________________

we are all worms, but i do believe i am a glow worm
M.r.G.5150 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


Similar Threads
Thread Thread Starter Forum Replies Last Post
high idle after header install nobodyfresh TJ General Discussion Forum 16 05-05-2011 06:51 PM
Slightly high idle (~1100rpm) MikalCarbine TJ Tech Forum 7 07-08-2010 07:58 PM
jeeps cold= ruff idle until warm, what gives 288sunny TJ Tech Forum 4 12-19-2009 02:54 PM
1998 Wrangler High Idle, w/ New TPS Broadcastmatt TJ Tech Forum 25 05-20-2009 09:07 PM
high idle when cold ...and warm peter angel YJ Tech Forum 2 11-23-2008 09:03 AM



» Network Links
»Jeep Parts
» Featured Product

All times are GMT -5. The time now is 09:42 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