high rpms when cranking - Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > General Jeep Discussions > Builders Corner

Join Wrangler Forum Today


Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 04-10-2011, 02:09 PM   #1
Newb
 
Join Date: Apr 2011
Location: thomasville
Posts: 2
Exclamation high rpms when cranking

i have a 2002 jeep tj with 4.0, has 84,000 miles on it. when i crank it up the motor runs up to 2000 rpms, then goes back to normal, mostly when the oil pressure gauge reads up to around 45-60 lbs, which is about 15-45 seconds. it just started doing this about a week ago, so i have tried fuel injection cleaner you add to gas and also cleaned the throttle body out with carb cleaner. any ideas?

coachwalt is offline   Quote
Old 04-10-2011, 05:01 PM   #2
mallcrawler

WF Supporting Member
::WF Moderator::
 
kjeeper10's Avatar
 
Join Date: Feb 2011
Location: Connecticut
Posts: 43,822
Quote:
Originally Posted by coachwalt
i have a 2002 jeep tj with 4.0, has 84,000 miles on it. when i crank it up the motor runs up to 2000 rpms, then goes back to normal, mostly when the oil pressure gauge reads up to around 45-60 lbs, which is about 15-45 seconds. it just started doing this about a week ago, so i have tried fuel injection cleaner you add to gas and also cleaned the throttle body out with carb cleaner. any ideas?
U clean the iac valve. It idles high when u start the jeep and then lowers after a few minutes. Maybe it's sticking.

__________________
37x12.5x17 MTR-Rock Krawler 3.5"
Coils-custom length X-Factor arms-Teraflex-Synergy steering-Rancho 5000X shocks-Adams front DS.
My 2007 2 Door Build
General lift discussion thread. Have a question, need help, issues, selecting a kit, ask here
Click HERE to become a WranglerForum Supporting Member!
kjeeper10 is online now   Quote
Old 04-11-2011, 06:36 PM   #3
Newb
 
Join Date: Apr 2011
Location: thomasville
Posts: 2
kjeeper10, thanks i tried that last night and it did fine, but this morning it revved up to 3000 rpms and the motor made a knocking sound for just a few minutes. this afternoon i drove it home from work and it went up to 2000rpms but settled down after a few moments. any other ideas?
coachwalt is offline   Quote
Old 04-11-2011, 07:41 PM   #4
mallcrawler

WF Supporting Member
::WF Moderator::
 
kjeeper10's Avatar
 
Join Date: Feb 2011
Location: Connecticut
Posts: 43,822
Did you disconnect the iac and see if there is a change? I'm no pro but been through a lot with my jeep. usually when something like this happens the check engine light comes on, I'm assuming that's not the case. If it's not a bad iac, check for the more common things that go bad like vacuum leaks or the other sensors like the throttle position sensor. Most of the time these trigger a CEL but you never know. I had a leaking intake manifold making this load whistling sound and no light and nobody could figure the damn thing out, untill I just had it replaced and that fixed my problem..
__________________
37x12.5x17 MTR-Rock Krawler 3.5"
Coils-custom length X-Factor arms-Teraflex-Synergy steering-Rancho 5000X shocks-Adams front DS.
My 2007 2 Door Build
General lift discussion thread. Have a question, need help, issues, selecting a kit, ask here
Click HERE to become a WranglerForum Supporting Member!
kjeeper10 is online now   Quote
Old 04-11-2011, 07:48 PM   #5
mallcrawler

WF Supporting Member
::WF Moderator::
 
kjeeper10's Avatar
 
Join Date: Feb 2011
Location: Connecticut
Posts: 43,822
And if you were to rev it to 3000 in neutral it misfires, I think thats normal and maybe what you heard
__________________
37x12.5x17 MTR-Rock Krawler 3.5"
Coils-custom length X-Factor arms-Teraflex-Synergy steering-Rancho 5000X shocks-Adams front DS.
My 2007 2 Door Build
General lift discussion thread. Have a question, need help, issues, selecting a kit, ask here
Click HERE to become a WranglerForum Supporting Member!
kjeeper10 is online now   Quote
Old 04-11-2011, 08:02 PM   #6
mallcrawler

WF Supporting Member
::WF Moderator::
 
kjeeper10's Avatar
 
Join Date: Feb 2011
Location: Connecticut
Posts: 43,822
This is a thread I dug up and I had to look closely cause it's almost identical with your ? And my first guess. It elaborates more on the IAC VALVE

http://www.jeepforum.com/forum/f11/e...ranked-961497/
__________________
37x12.5x17 MTR-Rock Krawler 3.5"
Coils-custom length X-Factor arms-Teraflex-Synergy steering-Rancho 5000X shocks-Adams front DS.
My 2007 2 Door Build
General lift discussion thread. Have a question, need help, issues, selecting a kit, ask here
Click HERE to become a WranglerForum Supporting Member!
kjeeper10 is online now   Quote
Old 04-12-2011, 04:02 AM   #7
Jeep Ninja

WF Supporting Member
 
scgeek12's Avatar
 
Join Date: Feb 2011
Location: Norfolk VA
Posts: 1,827
sounds like a vacuum leak to me, im no pro but to my knowledge the jeep (and most other cars) dont start reading any input from the sensors/computer untill it has warmed up a bit, then begins to take in readings from the computer,from what ive seen high idle at startup means its a vac. leak and the reason it goes to a normal idle rpm after 45ish seconds is the computer compensating for the leak once the car warms up and starts reading the sensor info

scgeek12 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
JUMPING RPM's... What's going on??? aturner088 General Jeep Discussion 3 04-06-2011 07:12 PM
high idle. Lariatryder YJ Tech Forum 8 12-06-2010 05:13 PM
High RPM's? surfskate21 General Jeep Discussion 12 11-29-2010 01:30 PM
high rpm's cab YJ Tech Forum 5 02-25-2009 05:46 PM
Highway rpms BARKDOG67 TJ Tech Forum 13 02-21-2009 09:29 PM



Download our Mobile App

» Featured Product

All times are GMT -5. The time now is 10:59 AM.


User Alert System provided by Advanced User Tagging v3.1.0 (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.

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