Tj 2.5 high idle - JeepForum.com
 
LinkBack Thread Tools
post #1 of 5 Old 01-25-2019, 09:53 PM Thread Starter
Broked
Registered User
 
Join Date: Jan 2019
Posts: 4
Tj 2.5 high idle

So, on a quest to turn my '01 4 banger into a hotrod i instaled some performance parts and now it has idle issues.

Symptoms are a resting idle around 1200 rmp. When reved rmps hang around 2000 for a few seconds before slowly dropping back to 1200. When coasting in neutral rpms will rev to 2000 and drop to 1200 repeatedly untill i come to a complete stop then they drop back to 1200. At first it was showing codes for tps low voltage and iac valve. Replaced both with no luck but no more codes. Checked all vacums and found no leaks.

Things i changed-
Header/muffler
Electric fan
4.0 throttle body
Hot coil/cap/rotor/thick wires/plugs gapped to .50 (kit recomended .65)
Home made cold air intake
Reset computer after install

Im stumped what the problem could be. I swaped the stock throttle body back on with no change in idle. The only thing i can think of is there is now sn aluminum fitting for the fan switch between the thermostat housing and temp sensor and now my temp reads lower than before. Could this be messing with the computer? Its reading around 180ish but gets a bit higher at times. Has a 195 thermostat.

Any ideas and sugestions would be much apretiated. Thanks

Broked is offline  
Sponsored Links
Advertisement
 
post #2 of 5 Old 01-26-2019, 06:09 AM
jtec
Registered User
2014 JK Wrangler 
 
Join Date: Oct 2017
Posts: 5,860
Mods are fun the computer and scanner take the quess work out.
We know The most important tool is a scanner... then
all you have to do is look at your scanner and read the live data...

vacuum leaks, sensor reports, voltages TPS and MAP, ECT, fuel trims, live data will help get thise mods working,

did I say VACUUM leak, we used to use carb spray to locate that, sometimes a throttle not letting TB return to idle position...

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
jtec is offline  
post #3 of 5 Old 01-26-2019, 09:02 AM
TJ4Jim
Registered User
1999 TJ Wrangler 
 
Join Date: Nov 2013
Location: Brookings
Posts: 769
Quote:
Originally Posted by Broked View Post
So, on a quest to turn my '01 4 banger into a hotrod i instaled some performance parts and now it has idle issues.

Symptoms are a resting idle around 1200 rmp. When reved rmps hang around 2000 for a few seconds before slowly dropping back to 1200. When coasting in neutral rpms will rev to 2000 and drop to 1200 repeatedly untill i come to a complete stop then they drop back to 1200. At first it was showing codes for tps low voltage and iac valve. Replaced both with no luck but no more codes. Checked all vacums and found no leaks.

Things i changed-
Header/muffler
Electric fan
4.0 throttle body
Hot coil/cap/rotor/thick wires/plugs gapped to .50 (kit recomended .65)
Home made cold air intake
Reset computer after install

Im stumped what the problem could be. I swaped the stock throttle body back on with no change in idle. The only thing i can think of is there is now sn aluminum fitting for the fan switch between the thermostat housing and temp sensor and now my temp reads lower than before. Could this be messing with the computer? Its reading around 180ish but gets a bit higher at times. Has a 195 thermostat.

Any ideas and sugestions would be much apretiated. Thanks
The 2 most common reasons for the high idle is an improperly seated intake/exhaust manifold or a vacuum system leak.

If you come to a fork in the road take it.
TJ4Jim is offline  
 
post #4 of 5 Old 01-26-2019, 04:04 PM Thread Starter
Broked
Registered User
 
Join Date: Jan 2019
Posts: 4
[QUOTE=jtec;40497779]Mods are fun the computer and scanner take the quess work out.
We know The most important tool is a scanner... then
all you have to do is look at your scanner and read the live data...

vacuum leaks, sensor reports, voltages TPS and MAP, ECT, fuel trims, live data will help get thise mods working,

did I say VACUUM leak, we used to use carb spray to locate that, sometimes a throttle not letting TB return to idle position...[/QUOTE thanks for the input im taking it into my local shop tuesday if i cant get it sorted out before then. They want $130 to run a diagnostic wich seems pricy. Hoping to find the problem before then. Ive checkedeverything that has vacuum with starter fluid and had no luck. I think it has to be the computer or a senser but no codes are showing.
Broked is offline  
post #5 of 5 Old 01-26-2019, 05:54 PM
TJ4Jim
Registered User
1999 TJ Wrangler 
 
Join Date: Nov 2013
Location: Brookings
Posts: 769
[quote=Broked;40498405]
Quote:
Originally Posted by jtec View Post
Mods are fun the computer and scanner take the quess work out.
We know The most important tool is a scanner... then
all you have to do is look at your scanner and read the live data...

vacuum leaks, sensor reports, voltages TPS and MAP, ECT, fuel trims, live data will help get thise mods working,

did I say VACUUM leak, we used to use carb spray to locate that, sometimes a throttle not letting TB return to idle position...[/QUOTE thanks for the input im taking it into my local shop tuesday if i cant get it sorted out before then. They want $130 to run a diagnostic wich seems pricy. Hoping to find the problem before then. Ive checkedeverything that has vacuum with starter fluid and had no luck. I think it has to be the computer or a senser but no codes are showing.
If you replaced the exhaust header and had a high idle afterwards the most common issue is the intake/exhaust is not seated properly which means removing and re-installing.

If you come to a fork in the road take it.
TJ4Jim is offline  
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.



Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Jeep Forums Replies Last Post
My goal is to get 25+ mpg from my 99 XJ with 30 x 9.5 R15 ATs Charley3 XJ Cherokee Technical Forum 3853 02-12-2019 09:15 AM
Howell TBI, California smog, high idle... Tremelune Jeep CJ Forum 11 01-19-2019 12:11 PM
High Oil Pressure and Rough Idle Zyurazek YJ Wrangler Technical Forum 28 10-10-2018 08:17 PM
High Idle at start. 2003 WJ 4.7 (Not HO) big_phil WJ Grand Cherokee Forum 6 06-23-2018 05:13 PM
High idle speed, p0507... maybe not TPS this time? tjwaterloo WK Grand Cherokee & XK Commander Forum 0 12-10-2017 09:35 AM

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 On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome