4.2 Nuttered Idle Issues - JeepForum.com
Search  
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 JeepForum.com > Models > Jeep Wrangler Forums > YJ Wrangler Technical Forum > 4.2 Nuttered Idle Issues

Savvy/Currie Aluminum Control ArmsROCK BOTTOM prices on LIFT KITS at Rockridge4wd!! WANT TO December Specials at Jeephut.com

Reply
Unread 09-15-2014, 09:09 PM   #1
ratat98
Registered User
1990 YJ Wrangler 
 
Join Date: Jan 2011
Location: , Oklahoma
Posts: 104
4.2 Nuttered Idle Issues

My YJ has been sitting for a couple weeks because I've been busy at work, and now when I get it out and drive it, it randomly idles around 500rpm sometimes, and other times around 1000. Before I let it sit, it was idling steady around 700-800ish with no problems. I've searched the threads and can't seem to find the same issue. Anyone have any ideas? Do I just need to clean the carb again?

__________________
I don't know why, but I just can't NOT own a jeep...
ratat98 is offline   Reply With Quote Quick reply to this message
Unread 09-15-2014, 09:18 PM   #2
Old4X
Registered User
1990 CJ7 
 
Join Date: Nov 2008
Location: Ga
Posts: 5,152
Run real gasoline, not ethanol laced gas, that cures most idling problems with carbs.

Do you have both return springs on the throttle arm? Are the throttle shafts gunk free? If not, carb cleaner will free then up.

Are your throttle shafts loose in the throttle body? This can make them stick and not return to proper position at idle. They can be re-bushed if worn.

And these engines will develop vacuum leaks if you look at them crosseyed. Check torque on carb baseplate and intake to head bolts. Also look for cracked vacuum lines.
__________________
418 miles on 19 gallons of gas. Can't beat the BBD !
Old4X is offline   Reply With Quote Quick reply to this message
Unread 09-15-2014, 09:23 PM   #3
ratat98
Registered User
1990 YJ Wrangler 
 
Join Date: Jan 2011
Location: , Oklahoma
Posts: 104
Thanks for all the advice! I didn't even think about ethanol..I'm pretty sure that's it since I just had to replace the carb on my chainsaw, due to what I've been told was, ethanol eating the seals. I've checked for vac leaks and checked the timing.. I'll squirt some carb cleaner on the goods, and let that sink in for a bit then get some octane booster and see if I can even find an ethanol free gas pump in this little town.
__________________
I don't know why, but I just can't NOT own a jeep...
ratat98 is offline   Reply With Quote Quick reply to this message
Unread 09-15-2014, 09:28 PM   #4
Old4X
Registered User
1990 CJ7 
 
Join Date: Nov 2008
Location: Ga
Posts: 5,152
Around boating areas usually have it. Outboards can't run ethanol fuel.
__________________
418 miles on 19 gallons of gas. Can't beat the BBD !
Old4X is offline   Reply With Quote Quick reply to this message
Unread 09-15-2014, 09:35 PM   #5
mike134
Registered User
1989 YJ Wrangler 
 
Join Date: Aug 2014
Location: Cleveland, OH
Posts: 1,307
I wouldn't hurt to spray carb cleaner around the vacuum lines to check for vacuum leaks though. It may still be a small intermittant vacuum leak.
mike134 is offline   Reply With Quote Quick reply to this message
Unread 09-15-2014, 10:15 PM   #6
ratat98
Registered User
1990 YJ Wrangler 
 
Join Date: Jan 2011
Location: , Oklahoma
Posts: 104
With it being nuttered, there really aren't a whole lot of vac lines that I need to check, but I will check them just to be sure. I need to rip a bunch of them out anyways...
__________________
I don't know why, but I just can't NOT own a jeep...
ratat98 is offline   Reply With Quote Quick reply to this message
Unread 09-15-2014, 11:40 PM   #7
mike134
Registered User
1989 YJ Wrangler 
 
Join Date: Aug 2014
Location: Cleveland, OH
Posts: 1,307
Quote:
Originally Posted by ratat98 View Post
With it being nuttered, there really aren't a whole lot of vac lines that I need to check, but I will check them just to be sure. I need to rip a bunch of them out anyways...
Doesn't the nutter bypass still have a vacuum line going to the carburetor? If so,then you need to make sure none of the vacuum lines leak, whether they are being used or not. A leak in any vacuum line will reduce manifold vacuum and allow extra air into your engine, both of which can cause problems elsewhere. You can remove the extra lines since they are prone to failure, but you have to plug up the ports that you no longer want to use.

This is a very good diagnostic to do because it is fast and free.
mike134 is offline   Reply With Quote Quick reply to this message
Unread 09-15-2014, 11:53 PM   #8
ratat98
Registered User
1990 YJ Wrangler 
 
Join Date: Jan 2011
Location: , Oklahoma
Posts: 104
Quote:
Originally Posted by mike134 View Post

Doesn't the nutter bypass still have a vacuum line going to the carburetor? If so,then you need to make sure none of the vacuum lines leak, whether they are being used or not. A leak in any vacuum line will reduce manifold vacuum and allow extra air into your engine, both of which can cause problems elsewhere. You can remove the extra lines since they are prone to failure, but you have to plug up the ports that you no longer want to use.

This is a very good diagnostic to do because it is fast and free.
Oh yeah most of mine are plugged already which is why I said that. There are the few left though that it needs. I just forgot how many were left. I miss the old vacuum line free days....
__________________
I don't know why, but I just can't NOT own a jeep...
ratat98 is offline   Reply With Quote Quick reply to this message
Unread 09-16-2014, 07:22 AM   #9
Mike Romain
Registered User
1986 CJ7 
 
Join Date: Nov 2007
Location: Off the Grid in Chester Grant, Nova Scotia, Canada
Posts: 13,945
A common issue that causes that is a chunk of dirt in one of the idle pickup tubes. The tubes have crimped ends that were made too small so they trap dirt. The fix is to drill or ream them out to at least .032". The test is to carefully look down the carb at idle and gently give it some throttle. If you see drops of gas instead of mists of gas, you have plugged tubes. Check out the site Jeep adventures under the hood by Dale Beckett for the fix directions. I used welding torch tip files to ream them but small drill bits can be found.
__________________
Mike
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
Mike Romain is offline   Reply With Quote Quick reply to this message
Unread 10-10-2014, 04:48 PM   #10
ratat98
Registered User
1990 YJ Wrangler 
 
Join Date: Jan 2011
Location: , Oklahoma
Posts: 104
Okay I've cleaned the carb, and tested the vac lines to no avail.....any other ideas?

Edit: and the carb did have some dirt stuck in it..blowing misty now instead of dripping..didn't help the problem though..
__________________
I don't know why, but I just can't NOT own a jeep...
ratat98 is offline   Reply With Quote Quick reply to this message
Unread 10-10-2014, 06:52 PM   #11
mike134
Registered User
1989 YJ Wrangler 
 
Join Date: Aug 2014
Location: Cleveland, OH
Posts: 1,307
Quote:
Originally Posted by Old4X View Post
Around boating areas usually have it. Outboards can't run ethanol fuel.
A lot of Marathon stations are still ethanol free!
mike134 is offline   Reply With Quote Quick reply to this message
Unread 10-10-2014, 07:21 PM   #12
Old4X
Registered User
1990 CJ7 
 
Join Date: Nov 2008
Location: Ga
Posts: 5,152
Quote:
Originally Posted by ratat98 View Post
Okay I've cleaned the carb, and tested the vac lines to no avail.....any other ideas?

Edit: and the carb did have some dirt stuck in it..blowing misty now instead of dripping..didn't help the problem though..
Have you done this?

http://www.jeeptech.com/engine/carter.html
__________________
418 miles on 19 gallons of gas. Can't beat the BBD !
Old4X is offline   Reply With Quote Quick reply to this message
Unread 10-10-2014, 07:40 PM   #13
ratat98
Registered User
1990 YJ Wrangler 
 
Join Date: Jan 2011
Location: , Oklahoma
Posts: 104
Quote:
Originally Posted by Old4X View Post
I did take the carb out and thoroughly clean it, however I didn't go to the extent of running wire down the tubes to clean them out. I'll have to do this once the rain stops pouring!
__________________
I don't know why, but I just can't NOT own a jeep...
ratat98 is offline   Reply With Quote Quick reply to this message
Unread 10-11-2014, 06:02 AM   #14
Mike Romain
Registered User
1986 CJ7 
 
Join Date: Nov 2007
Location: Off the Grid in Chester Grant, Nova Scotia, Canada
Posts: 13,945
Started after sitting for a while could indicate the gas filter started plugging up. The crud ethanol carries turns to varnish in a fuel filter if given enough time to evaporate away. Gas filters are cheap anyway and should be changed yearly on a daily driver. Just be sure you put it in level with the return line up top.
I would also crack open the gas cap to see if that fixes things. There is a $2.00 air filter on the gas tank vent that can cause the idle to drop down if plugged with dirt. It puts a vacuum on the gas tank starving the carb for fuel.
__________________
Mike
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
Mike Romain is offline   Reply With Quote Quick reply to this message
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.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:

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.


Thread Tools






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