Rough idle - 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 > Rough idle

Black Friday Sale - Deep Discounts from ExtremeTerrain.com6th Annual, Beat Your Wife to the Credit Card Sale!FS: Wrangler RGB Multicolor Fog Light LEDs: Awesome Effect

Reply
Unread 07-29-2012, 12:41 PM   #1
MPM19
Registered User
1995 YJ Wrangler 
 
Join Date: Mar 2012
Location: Newark, Delaware
Posts: 83
Rough idle

I have a fuel injected 1995 jeep wrangler with a rough idle. Any suggestions to smooth it out.
I have changed the spark plugs, wires, distributed cap and cleaned the throttle body.
I was thinking of changing the timing but can't find a solution to do so with the fuel injected engine. Any suggestions?
It's a 4 cyl

MPM19 is offline   Reply With Quote Quick reply to this message
Unread 07-29-2012, 04:31 PM   #2
mholmes7979
Registered User
1994 ZJ 
 
Join Date: May 2012
Location: Spring, Texas
Posts: 39
Check the air fittings to the fuel rail. Also check the other end around the carb. My 1994 4.0L would run ruff at idle and want to stall. Changed both air fittings & now it's good.
mholmes7979 is offline   Reply With Quote Quick reply to this message
Unread 07-29-2012, 06:23 PM   #3
pete1991YJ
Registered User
1991 YJ Wrangler 
 
Join Date: Mar 2012
Location: Niagara Falls, NY
Posts: 1,636
Does it happen when its warm or when its cold? All the time? It does make a difference - the computer does not listen to the O2 sensor until the engine is completely warmed up. If it starts running rough then, its a pretty good sign.

Other things to look for would be an exhaust leak - you would be surprised how many manifolds work loose especially at the back.

Ditto for vacuum leaks - spray around the ends of all hoses with some carb cleaner and listen for the idle to change - that would be a leak.

The timing is completely not adjustable on these - the computer does it all based on the sensors.

BTW can you read the computer codes? Its easy and free, all you need is the ignition key. Here's a video that shows how:
__________________
***--- Wrecking Crew member ---***
"I've prolly been around longer than you think"
pete1991YJ is offline   Reply With Quote Quick reply to this message
Unread 07-29-2012, 06:50 PM   #4
MPM19
Registered User
1995 YJ Wrangler 
 
Join Date: Mar 2012
Location: Newark, Delaware
Posts: 83
It will idle rough at all temps. It drives great though I fixed an exhaust leak last week and it helped a little.
It is a kind of a pulsing rough idle.
Is there a way to adjust the idle ?
MPM19 is offline   Reply With Quote Quick reply to this message
Unread 07-29-2012, 07:56 PM   #5
MPM19
Registered User
1995 YJ Wrangler 
 
Join Date: Mar 2012
Location: Newark, Delaware
Posts: 83
I got 12, 33, and of coarse 55.
MPM19 is offline   Reply With Quote Quick reply to this message
Unread 07-29-2012, 08:07 PM   #6
animal0307
Registered User
1991 YJ Wrangler 
 
Join Date: Nov 2011
Location: Arthur, IL
Posts: 470
I believe those are battery unhooked, AC clutch relay and end of code. They are all normal for most of us.

I second checking for vacuum leaks. I've heard to use a propane torch that has been cracked on but not lite for checking for leaks. Just wave it around the lines and listen for it to change.

What exhaust leak did you fix and how?
animal0307 is offline   Reply With Quote Quick reply to this message
Unread 07-29-2012, 08:58 PM   #7
MPM19
Registered User
1995 YJ Wrangler 
 
Join Date: Mar 2012
Location: Newark, Delaware
Posts: 83
Where the manifold meets the pipe kind if where the passenger sits, the bolt threads were stripped and a lot was getting out. I fixed it for the leak but mostly because of the squeaking noise it would make!!!
I put new hardware in, exhaust cement and cranked it down.
MPM19 is offline   Reply With Quote Quick reply to this message
Unread 07-31-2012, 01:53 PM   #8
MPM19
Registered User
1995 YJ Wrangler 
 
Join Date: Mar 2012
Location: Newark, Delaware
Posts: 83
Hey guys
I removed all of the fuel injectors cleaned them and put new o rings on.
It still idles rough so I don't know what it could be. It has 144,000 miles so I guess I'll just have I deal with it.
MPM19 is offline   Reply With Quote Quick reply to this message
Unread 07-31-2012, 08:34 PM   #9
Recoil
Registered User
1988 MJ Comanche 
 
Join Date: Oct 2007
Location: Indiana
Posts: 1,863
I just bought a 91 and was reading this forum to learn the world of the YJ. My new YJ also has a rough idle and I planned to clean the throttle body. Did you also remove the IAC take it apart and clean the plunger? I'm doing that this weekend. However I have more than a few exhaust leaks to repair on this thing which is getting the hot end of my welder next weekend.
__________________
www.indyorv.com

\/ \/ \/
EPIC
Recoil is offline   Reply With Quote Quick reply to this message
Unread 08-01-2012, 05:17 PM   #10
mholmes7979
Registered User
1994 ZJ 
 
Join Date: May 2012
Location: Spring, Texas
Posts: 39
Not trying to get you doing more than required but, compression, inspect plugs, wires , rotor & cap. After that injector cleaner and air leaks. If all this don't do it ?
mholmes7979 is offline   Reply With Quote Quick reply to this message
Unread 08-01-2012, 05:58 PM   #11
Yjmoneybucket
Registered User
1988 YJ Wrangler 
 
Join Date: May 2012
Location: Austin, TX
Posts: 6
I agree with the previous poster, check the iac (idle air control) motor. they also might call it an idle speed motor. when your throttle plate is closed, i.e. foot off gas, this motor is what allows air into the engine. the computer controls the idle by opening the plunger to various depths to allow air in. It is the idle control system on your Jeep. One key factor pointing to this being a problem is the jeep running okay at speed. it will run okay while your foot is on the gas, and run bad at stops. You can't really test it, but they aren't the most expensive thing to replace. we replace these motors at the shop i work at, all the time. Not just on Jeeps, but all cars, even the newer 2000's and up. They get dirty and "slow".
Yjmoneybucket is offline   Reply With Quote Quick reply to this message
Unread 08-01-2012, 06:32 PM   #12
Recoil
Registered User
1988 MJ Comanche 
 
Join Date: Oct 2007
Location: Indiana
Posts: 1,863
I've never replaced an IAC. All I've done is take them apart and. Lean all the gunk off the plunger. This works great everytime.
__________________
www.indyorv.com

\/ \/ \/
EPIC
Recoil is offline   Reply With Quote Quick reply to this message
Unread 08-01-2012, 07:58 PM   #13
MPM19
Registered User
1995 YJ Wrangler 
 
Join Date: Mar 2012
Location: Newark, Delaware
Posts: 83
I just cleaned the IAC and entire throttle body but nothing really changed although the piece was pretty dirty.
I'll probably try a compression test
MPM19 is offline   Reply With Quote Quick reply to this message
Unread 08-01-2012, 08:18 PM   #14
Recoil
Registered User
1988 MJ Comanche 
 
Join Date: Oct 2007
Location: Indiana
Posts: 1,863
Hmmm. Okay. Idle = air fuel and spark all firing in the right time. Air is good. Fuel is good. Spark is good. Time cannot be a problem. I'm voting spark. Something spark.
__________________
www.indyorv.com

\/ \/ \/
EPIC
Recoil is offline   Reply With Quote Quick reply to this message
Unread 08-01-2012, 09:46 PM   #15
deathtrap
Registered User
1993 YJ Wrangler 
 
Join Date: Jun 2011
Location: Hemet, CA.
Posts: 338
compression test/ cyl. leak test. bet you got a leaky or burnt valve. mine did.
deathtrap 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.