Low idle at stops - 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 02-08-2008, 11:12 AM   #1
Jeeper
 
98TJ's Avatar
 
Join Date: Oct 2007
Location: Vestal
Posts: 127
Low idle at stops

I have been experiencing this within the last week or so. When i drive down a hill if I ride it in second gear (as there are some curves I would rather not die on) when I come to a stop at the bottom my engine seems to drop to about 250-400 RPMs. Anyone ever experience this? It won't do it if I ride it in third just in second.

98TJ is offline   Quote
Old 02-08-2008, 11:33 AM   #2
Knows a couple things...

WF Supporting Member
 
Jerry Bransford's Avatar
 
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 34,387
Images: 2
Idle RPMs are controlled by the Idle Air Controller which is mounted onto the throttle body where it regulates the flow of air into the engine when your foot is not on the accelerator pedal. When it's not working correctly/engine is not idling properly, it generally only needs cleaning. Remove it (two small T-25 IIRC torx machine screws hold it on) and using a spray cleaner like throttle body cleaner or carb cleaner, together with a small brush or rag, clean its solenoide-actuated plunger of all the gunk you'll find on it. Then use the cleaner and a small brush like a baby bottle nipple brush to clean the oriface in the throttle body the IAC's plunger fits into. Once they're cleaned up and the IAC is mounted back onto the throttle body, use the rest of the cleaner to clean up the inside of the throttle body using the directions on the can.

The IAC is located is on the passenger side of the throttle body.

__________________
When you have a choice, buy American.

Jerry Bransford is offline   Quote
Old 02-08-2008, 11:22 PM   #3
Jeeper
 
98TJ's Avatar
 
Join Date: Oct 2007
Location: Vestal
Posts: 127
So i did as you described. It was a little gunked up but not as bad as expected. But to my surprise it still drops to about 250rpm as soon as I stop. It only does this on one hill. It runs sort of rough and feels like its gonna stall. As soon as I pop the gas to make the rpms jump it comes right back idling at 750. I just did a tune-up tonight and it still is doing it. I dunno
__________________


This is my jeep. There are many like it but this one is mine. My jeep is my best friend. It is my life. I must master it as I must master my life. Without me, my jeep is useless. Without my jeep I am useless. I must drive my jeep true. I must be better than the mud, who is trying to defeat me. I must conquer it before it conquers me. Before God I swear this creed: my jeep and myself are masters of the mud, we are the saviors of my life. So be it, until there is no more mud. Amen.
98TJ is offline   Quote
Old 02-09-2008, 12:16 PM   #4
Knows a couple things...

WF Supporting Member
 
Jerry Bransford's Avatar
 
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 34,387
Images: 2
Did you also clean the oriface the plunger fits into on the throttle body, and the inside of the throttle body? If they're clean, then the only other thing that can cause an erratic idle is the TPS (throttle position sensor) that is mounted 90 degrees clockwise from the IAC when looking at the throttle body from the top. The TPS gets dirty inside and can send erratic signals to the computer which will cause a bad idle. It can't be cleaned as it is sealed, it can only be replaced.
__________________
When you have a choice, buy American.

Jerry Bransford is offline   Quote
Old 02-10-2008, 04:40 AM   #5
Jeeper
 
Join Date: Nov 2006
Location: Chicago, IL
Posts: 8,286
Send a message via AIM to Triple88a Send a message via MSN to Triple88a Send a message via Yahoo to Triple88a Send a message via Skype™ to Triple88a
So Jerry you recommend spraying the electronics on the TB without a danger of it shorting out?

When i cleaned my TB i didnt do that, i only cleaned the throttle body it self but nothing else as i was afraid of it shorting out. I also have that problem. Once in a while it would drop down to ~ 300-400 rpm.
Triple88a is offline   Quote
Old 02-10-2008, 10:54 AM   #6
Knows a couple things...

WF Supporting Member
 
Jerry Bransford's Avatar
 
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 34,387
Images: 2
Quote:
Originally Posted by Triple88a View Post
So Jerry you recommend spraying the electronics on the TB without a danger of it shorting out?

When i cleaned my TB i didnt do that, i only cleaned the throttle body it self but nothing else as i was afraid of it shorting out. I also have that problem. Once in a while it would drop down to ~ 300-400 rpm.
I never said to "spray the electronics", I said to clean the IAC's solenoid actuated plunger, and the oriface in the throttle body it controls air flow through. And that if that didn't fix the eratic idle that replacing the TPS (throttle position sensor) would be the next logical step.
__________________
When you have a choice, buy American.

Jerry Bransford is offline   Quote
Old 02-10-2008, 10:56 AM   #7
Jeeper
 
Join Date: Nov 2006
Location: Chicago, IL
Posts: 8,286
Send a message via AIM to Triple88a Send a message via MSN to Triple88a Send a message via Yahoo to Triple88a Send a message via Skype™ to Triple88a
ok cool thanks.

Triple88a 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


Similar Threads
Thread Thread Starter Forum Replies Last Post
4.2 carb problems stray YJ Tech Forum 20 09-29-2014 11:02 PM
Low oil pressure at idle 97tjcse TJ Tech Forum 9 08-24-2009 11:12 PM
Idle speed 06R1Raven01TJ TJ Tech Forum 17 01-18-2009 03:39 AM
high idle when cold ...and warm peter angel YJ Tech Forum 2 11-23-2008 10:03 AM
92 wrangler won't idle toadster TJ Tech Forum 1 05-18-2007 10:18 AM



Download our Mobile App

» Network Links
»Jeep Parts
» Featured Product

All times are GMT -5. The time now is 11:42 AM.



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