Intermittent rough idle cold and hot. -
LinkBack Thread Tools
post #1 of 4 Old 10-08-2009, 04:19 PM Thread Starter
Registered User
bjl95mustang's Avatar
1998 ZJ 
Join Date: Dec 2005
Location: Austin, Texas
Posts: 805
Intermittent rough idle cold and hot.

In the mornings I will stop for gas about 1 mile from my house. When Iím pulling out of the lot it will stumble when I accelerate. But on the highway itís fine.

After I have been driving for a while and she is nice and warmed up I have some issues. When Iím sitting at a light my rpmís will drop and I can my engine stumble. It seems like itís miss firing. But once Iím moving she is just fine.

I just did a tune-up a couple months ago. Cap, rotor, plugs, and the wires are about 2 years old.

Where should I start checking? I have not had a CEL.

ZJ 98 5.2 LIMITED De-Badged

4.5" Lift: RE 4.5" springs,Iro rear 3.5 springs+1" spacer, RE shocks, All adjustable arms, IRO front track bar and HD bracket, Rear jks track bar, 1-Ton Steering, 242 tc, 33x12.5x15 GoodYear wrangler silent tires, 15" rock crawler rims, Aussie Locker For My 44A, 760X u-joint front axles.

Soon to come Lock Right Front Locker.

Jeep Inferno member #10

Texas Jeep Club Member #78
bjl95mustang is offline  
Sponsored Links
post #2 of 4 Old 10-08-2009, 04:46 PM
Registered User
1996 ZJ 
Join Date: Sep 2009
Location: Charlotte
Posts: 2,890
Have you cleaned the IAC? Checked out the TPS?
melk is offline  
post #3 of 4 Old 10-08-2009, 05:34 PM
Registered User
Join Date: Nov 2006
Location: Columbus
Posts: 1,546
when this starts happening, and you don't have any codes, I would start by taking your throttle body off and cleaning it so it looks like new. This could help, and the costs are free.

If that doesn't do the trick, then I would replace the IAC, then the TPS.

On a 98 (12 years old) the TB could be very carbonated and thus create problems. Clean out the small orface very well also.
cmonson is offline  
post #4 of 4 Old 10-08-2009, 05:55 PM
Registered User
1994 ZJ 
Join Date: Nov 2005
Location: Des Plaines, IL
Posts: 1,143
stumble upon acceleration usually indicates a tps that's on the way out. You can further diagnose by idling in park and very very slowly depressing the accelerator a little by little. Usually a bad tps will not notice this slow change until you've depressed the pedal a good bit. Then it will jump up to say 1K or so, so you should see a hesitation. When this jump occurs keep your foot at that position and release the pedal very slowly to the end, it will most likely cause a rough idle.

If changing the tps I would just get a new iac to go with it, two birds one stone.
gomes512 is offline  

Quick Reply

Register Now

In order to be able to post messages on the forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.

Email Address:


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.

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
94 GC 5.2 Rough idle when cold. smoulding ZJ Grand Cherokee Forum 3 11-09-2009 01:37 AM
03 WJ 4.0 Rough idle / cold knock hammertech ZJ Grand Cherokee Forum 9 11-26-2008 01:48 PM
rough idle when cold ? jeepunlimited ZJ Grand Cherokee Forum 1 07-26-2007 09:17 PM
Rough Idle - Intermittent, TPS bad? speedfreak04 ZJ Grand Cherokee Forum 8 12-18-2006 08:22 AM
Update: I-6 rough idle when cold VA_Jeepster ZJ Grand Cherokee Forum 0 09-09-2003 10:50 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