Jeep Wrangler Forum - Reply to Topic
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > TJ Jeep Wrangler Forum > TJ Tech Forum > New Jeeper and misfire

Join Wrangler Forum Today


Thread: New Jeeper and misfire Reply to Thread
Title:
  
Message:
Post Icons
You may choose an icon for your message from the following list:
 

Register Now

In order to be able to post messages on the Jeep Wrangler Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
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.



Additional Options
Miscellaneous Options

Topic Review (Newest First)
08-15-2010 10:14 AM
Jerry Bransford Some '97-98 TJ 4.0L engines came with a bad (weak) set of valve springs which will cause a VERY difficult to diagnose misfire on one or more cylinders. My '97 had that problem. Jeep has a TSB on the problem which basically replaces the bad valve springs which should cure it if that is the issue. The only thing is that if that problem has gone on long enough, it could have burned the valves or valve seats which would require a valve job too to completely correct the problem.
08-15-2010 05:52 AM
Sticks Good, you narrowed it down to Cyl #1.

Now I am working off an 03-06 4.0 engine control here, so your 97 may be different.

The ECM controls the ground leg for the injectors.

Key on, engine off, using a volt meter, first figure out which line is positive, and ground. Once you find the ground, set the volt meter to ohms and with one lead to the injector harness ground line, and the other to either battery negative or a good ground on the engine, rotate the engine around by hand and see if the ohm reading changes (should be OL or no continuity 99% of the time while you are rotating it, then a very brief moment of continuity). If you are getting a low ohm reading constantly, then your injector control wire is shorted to ground. Likewise if you can not find the positive wire - shorted or open (broken). If that is all testing good, then, try swapping the injector to another cylinder and see if the problem moves.

Once you isolated which is the problem, then start checking the wire harness for pinches or rub through. WCS it is an ECM problem. It could also be a dead cylinder (low compression).
08-14-2010 08:55 PM
bobbyearl
New Jeeper and misfire

Bought my first jeep this week. 97 Sahara 4.0L. Beyond excited about joining the club

Getting a misfire code. Individually unplugged and replugged the injectors with a noticeable difference in all except with the first cylinder, which makes me think that's the misfiring cylinder.

Replaced spark plugs, spark plug wires, distributor cap and rotator but still getting the code. Thinking it might be the injector but looking for any other suggestions.

Thanks everyone!

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


All times are GMT -5. The time now is 06:39 AM.



Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, and Grand Cherokee are copyrighted and trademarked to Chrysler Motors LLC.
Wranglerforum.com is not in any way associated with the Chrysler Motors LLC