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Misfire injector #1

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Old Aug 28, 2010 | 04:09 PM
  #1  
dk98classic's Avatar
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From: Smithton, IL
Year: 1998
Model: Cherokee
Engine: 4.0
Default Misfire injector #1

Been a busy Saturday. Had my codes read and received a P0201 and P0301. Replaced the cap, rotor, injector. Even went as far as replacing the cat and catback due to rust. I have a replacement header, just need to get that done. Oh, also replaced the before and aft O2 sensor. I haven't had the codes read/cleared yet, it still is running like it has a vacuum leak or a block. Arrrggg!
Any ideas?

Thanks part 2.
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Old Aug 28, 2010 | 04:39 PM
  #2  
ca441970's Avatar
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From: Easthampton, MA
Year: 1999
Model: Cherokee
Engine: 4.0
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Having the same issue with mine. P0301 code keeps returning. I replaced all the same parts as you did, minus the cat. Mine is getting a new head in the next couple months. Do a compression test. I have 2 low cylinders. 1 and 4. They are not crazy low, within specs, but making my idle about crappy. Weird thing about mine is sometimes it idles fine, then 1 minutes later misses, then fine at the next light. Pretty sure I have some sticky valves, or ones not seating right.
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Old Aug 28, 2010 | 05:50 PM
  #3  
dk98classic's Avatar
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From: Smithton, IL
Year: 1998
Model: Cherokee
Engine: 4.0
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Yeah, I was afraid it might be internal. I will be doing a compression test and going from there. Will be looking at junkyards for clean heads for future needs I guess.
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Old Aug 28, 2010 | 07:43 PM
  #4  
warthog's Avatar
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From: Keesler AFB, MS
Year: 1998 XJ
Model: Cherokee
Engine: 4.0L
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I went thru the same things you guys did and finally did a compression test and cylinder 1 had really low compression. 90 while the rest averaged 160. I tried everything and then finally removed the head and the machine shop found a big crack in between the two valves in cylinder 1. They also found another crack in cylinder 2 then i told them to stop looking because i had to buy a new head anyways. There could have been more. I guess the crack in cylinder 2 just wasn't causing any issues yet. I replaced the head and no more misfires. I am not saying you have a crack but like the last poster said. Do a wet and dry compression test and let use know what you got
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Old Sep 6, 2010 | 02:25 PM
  #5  
dk98classic's Avatar
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From: Smithton, IL
Year: 1998
Model: Cherokee
Engine: 4.0
Default Oh happy day

Yep, found cylinder 1 with 80 psi. The rest are at 150. Fantastic! Except for that #1... Also had oil on the spark plug.
Any ideas on a next step? I am looking/hoping it is just a cylinder head.

How long can this run with 1 missing cylinder? It is not a daily driver by any means. Just a errand runner when needed.
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