Cold start/idle issue -
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 > Models > Jeep Grand Cherokee & Commander Forums > WJ Grand Cherokee Forum > Cold start/idle issue

Black Magic Brakes is having an extended Black Friday Sale6th annual beat your wife to the credit cards sale!!Get ready!! CyberMonday deals are coming!!!

Unread 03-13-2012, 07:01 PM   #1
Registered User
2001 WJ 
Join Date: Nov 2006
Location: New Hartford, NY
Posts: 276
Wj Cold start/idle issue

Hey guys, I tried to do my own research on this one but I'd appreciate some fresh input. For reference, my WJ has 231,000 miles on it.

I am having an issue with cold starts (not necessarily cold temperatures per se, but say after the Jeep's been sitting 8 hours or more).

When making a cold start, the engine will not start unless I have my foot down on the accelerator ever so gently. If I use my foot to maintain around 1000 RPM's, and hold it there for about 45-60 seconds, I can then release the gas pedal and the Jeep will idle at about 600 RPM's on it's own (although it's a rough, rich smelling idle).

Once the Jeep is driven for 5-8 minutes or up to normal operating temperature, it will then idle perfectly. In gear and in park, once it warms up, it idles just as it should, smoothly and at the correct idle speed.

The problem existed for a few weeks with no CEL, then it finally tripped a code P0135 (1/1 upstream O2 sensor).

The following actions were taken:

-Cleaned battery connections and inspected grounds. All appear OK.
-Sprayed (liberally) throttle body cleaner into IAC valve slot in throttle body with Jeep running. Also applied it to throttle body itself and removed quite a bit of gummy crap from TB.
-Checked IAC wiring and connections (ok)
-Checked 1/1 O2 sensor fuse (#16) - It's intact. I pulled it and cleaned the contacts anyway.
-Changed factory upstream O2 sensor (which I found on only finger tight) with Denso 234-5488 replacement. I heard that Denso's were ok to use...
-Cleaned battery terminals AGAIN, removed positive cable while I was changing the sensor (took about 45 minutes). Applied brake with key on while POS cable was off (attempt to reset PCM).

After all this, the Jeep WILL now cold start without my foot on the gas, but it idles poorly (about 600 RPM cold) and sounds like it's ready to stall. After about 4 minutes the idle smooths out and comes up to about 900 RPM. The Jeep drives fine - has all the power it should and gets around 13.5 MPG.

What should I do? TPS, IAC? New battery? I heard about the wire loom that runs along the back of the engine but mine appears intact and not rubbing on anything, although I did NOT split it open and check each wire...yet.

Thanks for any input.

2001 WJ Laredo 4.0L 42RE NV242
nhcd538 is offline   Reply With Quote Quick reply to this message

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.

Thread Tools

Suggested Threads

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