Multiple cylinder misfire!!! - 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 > TJ Wrangler Technical Forum > Multiple cylinder misfire!!!

Year End Clearance Sale! Save 20%NEW!! HMF 50"-52" light bar mounting brackets!! Introducing MONSTALINER™ UV Permanent DIY Roll On Bed Line

Reply
Unread 10-03-2013, 10:19 AM   #1
SpecialTwinky
Registered User
 
Join Date: Oct 2013
Location: Bluffdale, Utah
Posts: 32
Multiple cylinder misfire!!!

I'm pretty sure that this has been discussed multiple times but I can't find what I am looking for. I have a 2002 jeep wrangler Sahara. It has a straight six and cylinders 1 3 4 5 &6. I can't figure out why it is doing it. I have changed the plugs and changed the ignition coil rail. I have also checked the cylinder compressions and they are all good. Does anybody know how I can fix this problem? Thanx for your help.

SpecialTwinky is offline   Reply With Quote Quick reply to this message
Unread 10-03-2013, 12:16 PM   #2
jkp
Registered User
2006 TJ Wrangler 
 
Join Date: Sep 2008
Location: Warner Robins, GA
Posts: 426
Check the crank position sensor. That's what the computer uses to fire the ignition at the correct time.
__________________
'92 Islander
'06 Rubicon
jkp is offline   Reply With Quote Quick reply to this message
Unread 10-03-2013, 04:25 PM   #3
SpecialTwinky
Registered User
 
Join Date: Oct 2013
Location: Bluffdale, Utah
Posts: 32
What do I need to do that? I have never checked a sensor before.
SpecialTwinky is offline   Reply With Quote Quick reply to this message
Unread 10-03-2013, 04:58 PM   #4
jkp
Registered User
2006 TJ Wrangler 
 
Join Date: Sep 2008
Location: Warner Robins, GA
Posts: 426
I think you can use an ohmmeter and test the resistance to see if it's shorted.

Other than that, there's not a good way to check it that I know of.

If it's the original one, I'd replace it.
__________________
'92 Islander
'06 Rubicon
jkp is offline   Reply With Quote Quick reply to this message
Unread 10-03-2013, 07:35 PM   #5
TJJP77
Registered User
2002 TJ Wrangler 
 
Join Date: Sep 2005
Location: Somewhere, MI
Posts: 1,820
You would need access to an oscilloscope to check the output of the CPS and verify that the signal has the proper "waveform" to diagnose it properly.
__________________
Chris
'02 Sahara
'06 Rubicon Unlimited
Sienna Jeep Club: Member #15
TJJP77 is offline   Reply With Quote Quick reply to this message
Unread 10-03-2013, 09:42 PM   #6
silver97tj
Registered User
1998 TJ Wrangler 
 
Join Date: Aug 2004
Location: midwest usa
Posts: 626
Hi all

Quick and dirty. wait till night and pop hood open, startup if is arcing you will see it right away..............................
__________________
1998 Blue TJ, 4 Cyl., Auto (30rh), Hardtop with installed Sunroof, mostly stock.
31x10.5x15 Mud Tires, TJ Rubicon springs, Mopar Deep Trans Pan and Cooler
Army Vet and proud of it! Have you served your country?
Support our Troops!! Thank You!!!
silver97tj is offline   Reply With Quote Quick reply to this message
Unread 10-03-2013, 09:55 PM   #7
TJJP77
Registered User
2002 TJ Wrangler 
 
Join Date: Sep 2005
Location: Somewhere, MI
Posts: 1,820
Quote:
Originally Posted by silver97tj View Post
Hi all

Quick and dirty. wait till night and pop hood open, startup if is arcing you will see it right away..............................
Little harder on an '02 - it doesn't have plug wires to arc. While it's possible to get some arcing from the coil to plug boots, it's not terribly likely if the coil rail is installed properly and the boots aren't torn or damaged.
__________________
Chris
'02 Sahara
'06 Rubicon Unlimited
Sienna Jeep Club: Member #15
TJJP77 is offline   Reply With Quote Quick reply to this message
Unread 10-03-2013, 10:07 PM   #8
goodwrenchdave
Registered User
2008 JK Wrangler 
 
Join Date: Aug 2013
Location: near Montreal, Quebec Canada
Posts: 428
So i'm assuming your setting p0300 at least and since you know the cylinders p0301,303,304,305,306? any others??
pull a sample of your gas from your fuel rail into a glass and let it sit for 1/2 hour. any contaminants, water? is it murky or clear, Do you have access to a scanner? can you check exhaust backpressure...it can cause misfires.
Do you drive it nice or hard.

how long have you had these misfires. any particular condition for them happening? highway speed, under acceleration, idle , hot , cold?

mileage please
goodwrenchdave is offline   Reply With Quote Quick reply to this message
Unread 10-03-2013, 10:42 PM   #9
SpecialTwinky
Registered User
 
Join Date: Oct 2013
Location: Bluffdale, Utah
Posts: 32
I just naught the jeep and it started misfiring a week or two after. I changed the rail and drive it around for thirty minutes that same day and it was fine. When I jumped in it the next day it happpened. It usually happens around twenty minutes of driving at any speed. It has just over 120k. I took it to a mechanic and he didn't know what was wrong. He said the wiring looked good to the ignition coil.
SpecialTwinky is offline   Reply With Quote Quick reply to this message
Unread 10-03-2013, 10:42 PM   #10
SpecialTwinky
Registered User
 
Join Date: Oct 2013
Location: Bluffdale, Utah
Posts: 32
Bought not naught. Sorry
SpecialTwinky is offline   Reply With Quote Quick reply to this message
Unread 10-03-2013, 10:45 PM   #11
chris142
Registered User
2002 TJ Wrangler 
 
Join Date: Jul 2010
Location: Apple Valley,Ca
Posts: 2,824
What type of plugs are in it now and what brand?

Usually a Crank senser works or it dont. Since it does run I would assume that its ok.

How much fuel pressure you got?
chris142 is offline   Reply With Quote Quick reply to this message
Unread 10-03-2013, 10:51 PM   #12
GOLENJEEPTJ
Running Secretly Amok!
 
GOLENJEEPTJ's Avatar
2002 TJ Wrangler 
 
Join Date: May 2007
Location: Ventura ,CA., California
Posts: 9,681
Have you thrown a cel and if so what were the codes?Your stating a multiple miss fire but nothing on a code?You need to elaborate a bit more.Is this a manual or an auto?
GOLENJEEPTJ is offline   Reply With Quote Quick reply to this message
Unread 10-03-2013, 11:22 PM   #13
goodwrenchdave
Registered User
2008 JK Wrangler 
 
Join Date: Aug 2013
Location: near Montreal, Quebec Canada
Posts: 428
Do you have a warranty as you just bought it?

sounds almost like it was sold because of this problem.

reading material.... not saying it's this as it has to be diagnosed but:

http://www.wjjeeps.com/tsb/tsb_wj_0900303.pdf
remember this can get expensive fast!

A very simple check is to just decarbonize first and check results.
goodwrenchdave is offline   Reply With Quote Quick reply to this message
Unread 10-04-2013, 07:47 AM   #14
aTX427
Registered User
1999 TJ Wrangler 
 
Join Date: Jul 2011
Location: Central, TX
Posts: 446
Run old school standard copper plugs, buy some Mopar wires, change the CPS with a Mopar sensor and check your ground straps. Stay away from the fancy plugs and cheap Chinese sensors.
aTX427 is offline   Reply With Quote Quick reply to this message
Unread 10-04-2013, 11:31 AM   #15
SpecialTwinky
Registered User
 
Join Date: Oct 2013
Location: Bluffdale, Utah
Posts: 32
I just put brand new Bosch Double Platinum plugs. The codes were p0300 301 303 304 305 306. What are mopar wires and how do I change them? And it is an automatic
SpecialTwinky is offline   Reply With Quote Quick reply to this message
Reply

Tags
help please , misfire cylinder 6 , sahara

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.