4.0 idling issues - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Wrangler Forums > YJ Wrangler Technical Forum > 4.0 idling issues

ROCK BOTTOM prices on LIFT KITS at Rockridge4wd!! WANT TO Alloy usa heavy duty ball joint kitsWe have FLASHLIGHTS! Great for your Emergency bag!

Reply
Unread 01-11-2009, 06:56 PM   #1
WVjeep94
Registered User
1978 CJ5 
 
Join Date: Apr 2008
Location: WV
Posts: 42
4.0 idling issues

When i first start up my 94 it idles and runs fine. Once you take it down the road for a while and come to a stop the idle jumps to about 1500 with the clutch in or if you take it out of gear. If you shut it off and let it sit for a little bit it starts up and idles fine again. Ive cleaned the throttle body with a rag and some throttle body cleaner and have also replaced the throttle positioning sensor. What should i do next?

WVjeep94 is offline   Reply With Quote Quick reply to this message
Unread 01-11-2009, 07:06 PM   #2
laybackman
Bikini Bridge Inspector
 
laybackman's Avatar
1995 YJ Wrangler 
 
Join Date: Dec 2002
Location: Massachusetts
Posts: 6,282
I would guess that the Idle Air Control (IAC) could be dirty also it is in the Throttle body also. Two torx screws hold it in place I beleive. Mine idled poorly so I pulled the IAC cleaned it and the bore it sits in with carb cleaner. Just be careful that the probe on the IAC does not get pulled out or it is junk. Clean the rpoobe preotion with CC and steel wool.
__________________
"Taking care of our veterans is a cost of war. If you can spend six trillion dollars sending people to war, you can spend a few billion dollars taking care of them when they come home"
Sen. Bernie Sanders (I-Vt.)

If what doesn't kill you, makes you stronger, I should be able to bench press a Grand Cherokee by now!
laybackman is offline   Reply With Quote Quick reply to this message
Unread 01-21-2009, 07:23 PM   #3
WVjeep94
Registered User
1978 CJ5 
 
Join Date: Apr 2008
Location: WV
Posts: 42
Alright I cleaned the throttle body got a new IAC and TPS and am still idling after running for a little bit at about 1200-1500. I pulled it in the car port opened the hood and could get the idle to come down to normal by putting a litte pressure on the butterfly on the throttle body. Can I replace the spring on that thing or what else could it be?
WVjeep94 is offline   Reply With Quote Quick reply to this message
Unread 01-21-2009, 08:00 PM   #4
laybackman
Bikini Bridge Inspector
 
laybackman's Avatar
1995 YJ Wrangler 
 
Join Date: Dec 2002
Location: Massachusetts
Posts: 6,282
Quote:
Originally Posted by WVjeep94 View Post
Alright I cleaned the throttle body got a new IAC and TPS and am still idling after running for a little bit at about 1200-1500. I pulled it in the car port opened the hood and could get the idle to come down to normal by putting a litte pressure on the butterfly on the throttle body. Can I replace the spring on that thing or what else could it be?
You got three cables going to the TB. Are any of them binding up?

The spring on the throttle arm whiuch is opposite the TPS might need a shot of carb cleaner then a shot of lube like silicon spray.
__________________
"Taking care of our veterans is a cost of war. If you can spend six trillion dollars sending people to war, you can spend a few billion dollars taking care of them when they come home"
Sen. Bernie Sanders (I-Vt.)

If what doesn't kill you, makes you stronger, I should be able to bench press a Grand Cherokee by now!
laybackman is offline   Reply With Quote Quick reply to this message
Unread 01-21-2009, 08:07 PM   #5
WVjeep94
Registered User
1978 CJ5 
 
Join Date: Apr 2008
Location: WV
Posts: 42
That might be my problem right there I only have one cable going to the throtte body. Is there supposed to be more than one spring too? I think i might need a picture.
WVjeep94 is offline   Reply With Quote Quick reply to this message
Unread 01-21-2009, 09:12 PM   #6
WVjeep94
Registered User
1978 CJ5 
 
Join Date: Apr 2008
Location: WV
Posts: 42
So you have the cable from the gas pedal what other cables are supposed to be on there?
WVjeep94 is offline   Reply With Quote Quick reply to this message
Unread 01-21-2009, 09:40 PM   #7
Mean Max
Don't poke the bear
 
Mean Max's Avatar
1991 YJ Wrangler 
 
Join Date: Jul 2007
Location: Stuart, Florida
Posts: 13,682
Quote:
Originally Posted by WVjeep94 View Post
So you have the cable from the gas pedal what other cables are supposed to be on there?
Just the one. You could have three, if there were a cruise control cable, and a kickdown cable for an automatic tranny, but you probably won't have but the one.

The OE spring should be plenty, but you can add another if you like, it won't hurt anything, it'll just make for a stiffer throttle pedal & possibly a numb right leg.

Check thoroughly for a vacuum leak. Any "un-metered" air between the throttle plate & cylinder head will raise your idle. The more significant the leak, the higher the uncontrollable idle will be.


__________________
Click here to see all of my different albums on Photobucket.
Choose any album to see all of my pics!


Quote:
Originally Posted by UltimatE View Post
Max has a picture of every Jeep part ever made.
Quote:
Originally Posted by Benderff View Post
No one here knows what they are talking about. You should try Pirate 4x4 they will be happy to help you.

There is no situation that cannot be improved with a small but well-placed explosive.
Mean Max is online now   Reply With Quote Quick reply to this message
Unread 01-21-2009, 09:46 PM   #8
WVjeep94
Registered User
1978 CJ5 
 
Join Date: Apr 2008
Location: WV
Posts: 42
Wouldnt a vaccum leak or unmetered air cause it to do this all the time right at start up? Instead of going away if you shut it off and wait a few minutes and start it back. When i shut it off for a little bit i can start it back up and it idles fine.
WVjeep94 is offline   Reply With Quote Quick reply to this message
Unread 01-21-2009, 09:53 PM   #9
Mean Max
Don't poke the bear
 
Mean Max's Avatar
1991 YJ Wrangler 
 
Join Date: Jul 2007
Location: Stuart, Florida
Posts: 13,682
A "cold/cool" engine will idle lower & require more air to maintain the correct idle. This may explain why it idles okay when first started. A warmer engine (after having gone down the road a little way, as you described) would require less air (like from the idle motor circuit) to maintain correct idle. A small vacuum leak could be allowing just enough air into the intake so that the idle motor can't cut enough air out to compensate. In this time of year when the engine cools off so much faster after shut down, the problem my become a bit more invisible.
__________________
Click here to see all of my different albums on Photobucket.
Choose any album to see all of my pics!


Quote:
Originally Posted by UltimatE View Post
Max has a picture of every Jeep part ever made.
Quote:
Originally Posted by Benderff View Post
No one here knows what they are talking about. You should try Pirate 4x4 they will be happy to help you.

There is no situation that cannot be improved with a small but well-placed explosive.
Mean Max is online now   Reply With Quote Quick reply to this message
Unread 01-21-2009, 10:04 PM   #10
WVjeep94
Registered User
1978 CJ5 
 
Join Date: Apr 2008
Location: WV
Posts: 42
thanks for the reply Ill take a look tomorrow
WVjeep94 is offline   Reply With Quote Quick reply to this message
Unread 01-21-2009, 10:15 PM   #11
Mean Max
Don't poke the bear
 
Mean Max's Avatar
1991 YJ Wrangler 
 
Join Date: Jul 2007
Location: Stuart, Florida
Posts: 13,682
Quote:
Originally Posted by WVjeep94 View Post
thanks for the reply Ill take a look tomorrow
If you spray some throttle body cleaner arond your vacuum fittings & lines while it's running, the leak can usually be detected by listening for the idle to fluctuate as it sucks up the cleaner through the leak.

__________________
Click here to see all of my different albums on Photobucket.
Choose any album to see all of my pics!


Quote:
Originally Posted by UltimatE View Post
Max has a picture of every Jeep part ever made.
Quote:
Originally Posted by Benderff View Post
No one here knows what they are talking about. You should try Pirate 4x4 they will be happy to help you.

There is no situation that cannot be improved with a small but well-placed explosive.
Mean Max is online now   Reply With Quote Quick reply to this message
Unread 01-22-2009, 08:03 AM   #12
laybackman
Bikini Bridge Inspector
 
laybackman's Avatar
1995 YJ Wrangler 
 
Join Date: Dec 2002
Location: Massachusetts
Posts: 6,282
Quote:
Originally Posted by WVjeep94 View Post
That might be my problem right there I only have one cable going to the throtte body. Is there supposed to be more than one spring too? I think i might need a picture.
EDIT EDIT You MAY have UP TO three cables on your TB. I am dummy for not makiing that clear. Try cleaning the spring then check the MAP sensor vacuum hose and start looking for any leaks with spray as mentioned a loose TB etc. Did you check for any trouble codes?
__________________
"Taking care of our veterans is a cost of war. If you can spend six trillion dollars sending people to war, you can spend a few billion dollars taking care of them when they come home"
Sen. Bernie Sanders (I-Vt.)

If what doesn't kill you, makes you stronger, I should be able to bench press a Grand Cherokee by now!
laybackman is offline   Reply With Quote Quick reply to this message
Unread 01-22-2009, 07:00 PM   #13
WVjeep94
Registered User
1978 CJ5 
 
Join Date: Apr 2008
Location: WV
Posts: 42
I figured it out today, I had a couple intake manifold bolts loose. Tightened them up and it seems to be doing fine now. Thanks
WVjeep94 is offline   Reply With Quote Quick reply to this message
Unread 01-23-2009, 03:09 PM   #14
Mean Max
Don't poke the bear
 
Mean Max's Avatar
1991 YJ Wrangler 
 
Join Date: Jul 2007
Location: Stuart, Florida
Posts: 13,682
Quote:
Originally Posted by WVjeep94 View Post
I figured it out today, I had a couple intake manifold bolts loose. Tightened them up and it seems to be doing fine now. Thanks
That would be the vacuum leak then!

Glad you got it all sorted out, and posted your findings/results! You may be helping somebody else out in the future!



__________________
Click here to see all of my different albums on Photobucket.
Choose any album to see all of my pics!


Quote:
Originally Posted by UltimatE View Post
Max has a picture of every Jeep part ever made.
Quote:
Originally Posted by Benderff View Post
No one here knows what they are talking about. You should try Pirate 4x4 they will be happy to help you.

There is no situation that cannot be improved with a small but well-placed explosive.
Mean Max is online now   Reply With Quote Quick reply to this message
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
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


Suggested Threads





Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.