4.0 stumble/surge off idle - JeepForum.com

 
LinkBack Thread Tools
post #1 of 12 Old 09-15-2009, 03:41 PM Thread Starter
RDWhin01SS
Registered User
1999 WJ 
 
Join Date: Aug 2008
Location: IL
Posts: 4
4.0 stumble/surge off idle

Please help, this has been driving me crazy. I have a 99 wj with a 4.0 and it will stumble and stall when trying to idle. if given a little gas then let off it seems that it cant find where it should idle, but when it does it idles perfectly fine. It also has a hesitation when first accelerating, and occasionally when starting it cranks for a long time before starting. I have cleaned the throttle body and replaced the iac, tps, and map.

RDWhin01SS is offline  
Sponsored Links
Advertisement
 
post #2 of 12 Old 09-15-2009, 05:33 PM
4Slow9erHybrid
Registered User
1997 ZJ 
 
Join Date: May 2008
Location: Hopkinton
Posts: 745
Quote:
Originally Posted by RDWhin01SS View Post
Please help, this has been driving me crazy. I have a 99 wj with a 4.0 and it will stumble and stall when trying to idle. if given a little gas then let off it seems that it cant find where it should idle, but when it does it idles perfectly fine. It also has a hesitation when first accelerating, and occasionally when starting it cranks for a long time before starting. I have cleaned the throttle body and replaced the iac, tps, and map.
Does this stumbling happen shortly after starting the engine (2-3 mins) and lasts a short time 1-2mins. Most likely the upstream O2 sensor. You can diagnose this by disconnecting the O2 sensor for a few days (don't drive a 1000 mi like this). If the stubling symptoms disappear, you diagnosed a failing O2 sensor. Replace with original MOPAR only!

1997 JGC Laredo 4.0 4x4 99900mi * 0W30 German Castrol since 75k * 225/75/R15 Firestone Destination AT on Ravine rims * winter 235/75/R15 Bridgestone Blizzak DM-V1 * UC suspension * Monroe Reflex Monotube shocks * factory skids * KOR steering brace * rear Addco SB * Magnaflow cat and cat back system * complete 5.9 interior
4Slow9erHybrid is offline  
post #3 of 12 Old 09-15-2009, 05:44 PM Thread Starter
RDWhin01SS
Registered User
1999 WJ 
 
Join Date: Aug 2008
Location: IL
Posts: 4
thanks i will give it a try, yea it starts shortly after starting the engine and usually just occurs when coming to a stop or at very slow speeds where you are on the gas a little then back out of it... like in a drive thru, or traffic
RDWhin01SS is offline  
post #4 of 12 Old 12-07-2009, 09:31 PM
steveheibel
Registered User
1999 WJ 
 
Join Date: May 2009
Location: Michigan
Posts: 84
I was wondering if you ever found the fix for this
steveheibel is offline  
post #5 of 12 Old 12-07-2009, 11:11 PM
StellaTheZJ
Registered User
1996 ZJ 
 
Join Date: Jan 2009
Location: BC
Posts: 629
This sounds a lot like a TPS issue. They are basically sliding switch, and they wear out in the region with most of the "sliding." The small section just off idle is rubbed every time you move off idle, and no other area is worn so much. This can be checked with a multimeter. Check your manual for the specs.
StellaTheZJ is offline  
post #6 of 12 Old 12-08-2009, 02:49 AM Thread Starter
RDWhin01SS
Registered User
1999 WJ 
 
Join Date: Aug 2008
Location: IL
Posts: 4
i have yet to find a fix for this. the 02 sensors are both new, tps, iac, & map are fine, fuel pressure good, vaccuum is fine as well. has anyone else expierienced this and have more info?
RDWhin01SS is offline  
post #7 of 12 Old 12-08-2009, 08:04 AM
4Slow9erHybrid
Registered User
1997 ZJ 
 
Join Date: May 2008
Location: Hopkinton
Posts: 745
Quote:
Originally Posted by RDWhin01SS View Post
the 02 sensors are both new
what brand O2 sensors?

1997 JGC Laredo 4.0 4x4 99900mi * 0W30 German Castrol since 75k * 225/75/R15 Firestone Destination AT on Ravine rims * winter 235/75/R15 Bridgestone Blizzak DM-V1 * UC suspension * Monroe Reflex Monotube shocks * factory skids * KOR steering brace * rear Addco SB * Magnaflow cat and cat back system * complete 5.9 interior
4Slow9erHybrid is offline  
post #8 of 12 Old 06-20-2011, 12:12 PM
fotonm
Registered User
 
Join Date: Jun 2011
Location: Albuqueruqe
Posts: 37
After having this same problem on my 94 with a 5.2 I changed EVERYTHING that people have been talking about on here the TPS, New Tranny, New fuel filter, New fuel pressure regulator. Sometimes it would run great then other times just very sluggish and especially between about 1000 to the 2000 rpm mark. It didnt matter if it was hot or cold just very frustrating and intermittent.

Well I started to suspect a vacuum leak. While monkeying with the vacuum lines and wiggling them I got a surge and thought I was on to it. It wasn't the vacuum after all.

It was the wires that go into the TPS and when I would wiggle them it would surge and even cut off the engine. I unplugged it and Ohmed out the wires while my ohm meter was plugged into and wiggled the wires and I didnt get any Resistance drop. I figure out that the pin that comes out from the ground part of the TPS was not making a good contact with the connector. When it was not making a good solid contact I would get the problem.

You can fix this one of two ways.... you can replace the entire plug assembly to one where the female end of the connectors make a better contact or you can take up the slack in the now too loose female end with a small piece of wire inserted into the tooled out female end (lol) and now it wont be like a hotdog in a hallway and will make a good ground. Plugged it all back in and now runs like it should with full power all the way through the spectrum.

This worked for me so you may try this!! Its a connection and grounding problem not an actual prob with any of the devices.

if your grounding and connections in that TPS are not solid it spikes all up and down sending the wrong voltage to the rest of the injection system.
fotonm is offline  
post #9 of 12 Old 04-18-2013, 04:08 PM
Christianofojai
Registered User
2000 WJ 
 
Join Date: Nov 2012
Location: Ojai
Posts: 75
I’m having the same problem. It’s been driving me crazy. I noticed this problem with mine is intermittent and when it happens it’s also acompined by the smell of gas out of the tail pipe. I thought O2 sensor butt after replacing them all it still does it.

V8s are like tampons. Every p**y has one.
6 in a row makes it go.
My lug-nut has more torque than your v8
Christianofojai is offline  
post #10 of 12 Old 09-29-2014, 10:27 AM
Goldendust
Registered User
2004 XJ Cherokee 
 
Join Date: Sep 2014
Location: Savage
Posts: 1
I'm not sure how to make a new post, so I'll post my question here and hope someone has an idea as to what's going on with my 2004 Jeep Grand Cherokee, 4.0Liter.

The Issue:
Slow, sluggish starts. Sometimes, it starts right up, but if it sat a couple days, it usually requires an attempt or two at getting it going. Once it's been on and running, it's fine and starts right away.

The Current Fixes:
New battery, battery cables and terminals, new starter, cleaned throttle body, injection cleaners, spark plugs.

Any thoughts are appreciated. Thanks!
Goldendust is offline  
post #11 of 12 Old 09-30-2014, 06:35 AM
AVR2
Web Wheeler
1993 ZJ 
 
Join Date: Apr 2007
Location: UK
Posts: 3,634
Fuel pump getting old, and taking time to build up enough pressure for the first start after it's sat for a day or two?

Next time you have to start it after letting it sit, you might try letting the pump prime 2-3 times before actually starting the engine. If it starts straight away every time after doing that, then that's likely your issue.

BTW, since you have a 2004 Grand, you have a WJ, not a ZJ
AVR2 is offline  
post #12 of 12 Old 02-02-2015, 06:41 PM
Goldentwo
Registered User
1994 FSJ Cherokee 
 
Join Date: Feb 2015
Posts: 2
I've had this problem in the past and it was the EGR valve. Drove me crazy too. Hope this helps since nobody has mentioned it yet.
Goldentwo 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









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
Idle surge/stumble steveheibel WJ Grand Cherokee Forum 49 03-10-2010 03:54 PM
Slight idle surge 5.2 V8 lma1973 ZJ Grand Cherokee Forum 2 10-01-2008 09:12 PM
4.0 97 zj Idle surge when warmed up. sadass ZJ Grand Cherokee Forum 2 09-29-2008 02:05 PM
99 WJ Limited 4.7 idle surge dacecil ZJ Grand Cherokee Forum 1 11-25-2007 01:37 PM
Idle Surge??? 2k4silverubi ZJ Grand Cherokee Forum 4 05-15-2007 12:35 PM

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