Problems w/ new rebuilt 4.0 liter 1999 WJ - JeepForum.com

 
LinkBack Thread Tools
post #1 of 5 Old 01-20-2014, 02:39 PM Thread Starter
durnjeep
Registered User
 
Join Date: Jan 2014
Location: Elizabethton
Posts: 3
Problems w/ new rebuilt 4.0 liter 1999 WJ

I had a rebuilt motor put in it with a new WATER PUMP, RADIATOR, TIMING CHAIN, 2 O2 SENSORS, TPS, IAC, PLUGS and BATTERY. Starts fine, highways speeds fine, just bogs out when cold or warm at low speeds (0-15 mph) for about 5 seconds to 1 minute. If I let off of the accelerator the rpms are fluctuating between 300 and about 700 and will occasionally just die if I don't put it in neutral OR let off gas for a split second then go WOT. When I push the accelerator in normally the rpm's are at about 1K when they should be at 2K. But then it just picks back up again, and it doesn't do it again until I turn it off and restart it. Again, it still does it even if it's warm (I shut it off and get gas quick) and usually happens at about 0-15 mph but never at highway speeds. The mechanic that did all the work on it is at a loss right now, and has had it for about 5 months. By turning key on/off 3 times I get P0141 and P0161 codes (both downstream o2 sensor heater element malfunction.) Looks like they pertain to the O2 heaters, but not sure if that would cause this. There are 2 mini Cats. at the manifold both of which are about 700 degrees F. The last cat. w/ no o2 sensors is about 400 degrees F. Mechanic said fuel pressure tests fine at the rail.

durnjeep is offline  
Sponsored Links
Advertisement
 
post #2 of 5 Old 01-31-2014, 09:38 PM
monte350
Registered User
1997 ZJ 
 
Join Date: Jan 2014
Location: willimantic
Posts: 333
my wifes 97 grand with the 4.0 would start fine when cold but when it warmed up the rpm would drop to about 300 to 500 and barely idle. i unplugged the first o2 sensor while it was running like that and it started idling like normal. replaced it with a new sensor and it never did it again. i never had any codes in the pcm though. it was a guess by a mechanic buddy of mine, but it worked.
monte350 is offline  
post #3 of 5 Old 01-31-2014, 10:16 PM
uberxj92
Registered User
1992 XJ Cherokee 
 
Join Date: Oct 2012
Location: umatilla
Posts: 1,961
Sounds like maybe Tps. Do you have a cel? How's your battery and alt?

http://www.jeepforum.com/forum/f177/92-xj-sadness-2075657/index2.html
uberxj92 is offline  
post #4 of 5 Old 02-01-2014, 09:52 AM Thread Starter
durnjeep
Registered User
 
Join Date: Jan 2014
Location: Elizabethton
Posts: 3
Ok, a quick update. It turns out the mechanic only replace one downstream O2 sensor. So I unplugged both downstreams, and that had a very minimal effect. Then unplugged both upstreams and that fixed the problem. I dont have the $400 to replace them right now, but it runs pretty good without them. Maybe a little rich but nothing serious.
durnjeep is offline  
post #5 of 5 Old 02-07-2014, 08:27 AM
tbk5000
Registered User
1995 YJ Wrangler 
 
Join Date: Feb 2011
Location: NAPERVILLE
Posts: 26
You want to watch running it to long with the o2's unplugged because the over fueling can burn your cats out.

White jeep club member 157
tbk5000 is offline  
Reply

Tags
1999 , 4.0 , help needed , rebuild , stall

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



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