Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here XJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.

need help with misfires!

Thread Tools
 
Search this Thread
 
Old 07-20-2012, 11:28 PM
  #1  
Senior Member
Thread Starter
 
70hemicuda's Avatar
 
Join Date: Feb 2012
Location: newjersey
Posts: 627
Likes: 0
Received 3 Likes on 3 Posts
Year: 2000
Model: Cherokee
Engine: I6
Default need help with misfires!

I got the check engine light about a week ago and the only thing I noticed was a small rough-ness in the idle, nothing major. It runs fine, no loss of power at all. the rough idle happens all the time, even when the engine is cold. I got it scanned and pulled the codes p0300, p0302, p0303, p0305, and p0306. From what i understand its a misfire, and the cause could be a couple of things. I replaced the plugs in march after getting codes for cylinders 1,2,3,and 4 and up until last week it was fine. I read and saw that it could be the cam sensor acting up ??? didnt find any leaks either. I was hoping that you guys could help me out. from what i have searched this seems to be a pretty common thing....
thanks!
Old 07-21-2012, 06:39 AM
  #2  
CF Veteran
 
tjwalker's Avatar
 
Join Date: Nov 2010
Location: In the middle of Minnesota!
Posts: 5,804
Received 99 Likes on 88 Posts
Year: 1999
Model: Cherokee
Engine: 4.0
Default

The key to me in all of your codes is the random misfire P0300. Whenever I see those, I suspect one "common" root cause which is then also responsible for the single cylinder misfires (P0302, P0303, P0305, P0306).

First thing I would do for this is to test fuel pressure. For a 2000, you should have 49 psi, plus or minus 5 psi. You need to start the process of elimination and fuel pressure absolutely needs to be ruled in or out early in this process.

A vacuum leak or unusually low fuel pressure could be a cause here.
Old 07-22-2012, 06:09 PM
  #3  
Senior Member
Thread Starter
 
70hemicuda's Avatar
 
Join Date: Feb 2012
Location: newjersey
Posts: 627
Likes: 0
Received 3 Likes on 3 Posts
Year: 2000
Model: Cherokee
Engine: I6
Default

I didn't find any leaks. how do you check the fuel pressure?
Old 07-22-2012, 07:23 PM
  #4  
CF Veteran
 
tjwalker's Avatar
 
Join Date: Nov 2010
Location: In the middle of Minnesota!
Posts: 5,804
Received 99 Likes on 88 Posts
Year: 1999
Model: Cherokee
Engine: 4.0
Default

Originally Posted by 70hemicuda
I didn't find any leaks. how do you check the fuel pressure?
Rent a fuel pressure gauge from your local parts store. Install it on the schrader valve on the fuel rail under the hood. Super easy. Call around, you will find a store that rents this tool inexpensively.
Old 07-22-2012, 07:32 PM
  #5  
Senior Member
Thread Starter
 
70hemicuda's Avatar
 
Join Date: Feb 2012
Location: newjersey
Posts: 627
Likes: 0
Received 3 Likes on 3 Posts
Year: 2000
Model: Cherokee
Engine: I6
Default

okay thanks. there's an autozone up the road from me so I will be going there.
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
jmarzo
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
16
10-18-2022 04:11 PM
Juan2387
Modified XJ Cherokee Tech
0
09-25-2015 01:44 PM
bigVOLharp98
Cherokee Chat
5
09-20-2015 10:47 PM
Fiskdog
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
1
09-20-2015 12:26 PM
roystondrake
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
2
09-17-2015 11:14 AM

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 


Quick Reply: need help with misfires!



All times are GMT -5. The time now is 09:23 PM.