Mis at idle / stumble at idle

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Nov 28, 2011 | 09:28 PM
  #1  
This all started when the jeep wouldn't start so i went ahead and replaced the cps and camshaft sensor. But during the camshaft sensor replacement being the dip I am, I pulled the drive gear with it and but it back wrong causing the engine to continue to start and stall until I played with the camshaft sensor which continued to stall untili pulled the gear drive again and 1st spark plug to zero it at the top of the compression stroke. From that time she's went vroom every start but has a mis at idle and at some moments pretty sporadic Mis's back to back.

So far ive replaced
- spark plugs
- upgraded to 784 injectors
- removed and cleaned throttle body and IAC

the injectors test good for power and I can't find any wires rubbed threw on the harness that may be grounding. What else could I be missing. It hard to believe it could be anything else and it would just pop up after this. My head tells me with all the stalled starts my timing chain has jumped but my mechanic (I work at a golf course ) says its hard for him to believe since it runs good when I'm on the gas. Any ideas? Thanks
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Nov 28, 2011 | 10:07 PM
  #2  
BUMP! Someone please help this guy cuz I've got no one to wheel with until then.
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Nov 28, 2011 | 10:14 PM
  #3  
In your post you mentioned that you replaced your spark plugs. Did you change wires, cap and rotor( if applicable) I had a very similar miss and that cured my hiccups in my xj.
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Nov 28, 2011 | 11:02 PM
  #4  
Quote: In your post you mentioned that you replaced your spark plugs. Did you change wires, cap and rotor( if applicable) I had a very similar miss and that cured my hiccups in my xj.
I wish I could but my xj is distributorless with no wires and only a coil rail. But what would of caused it to fail when it something failed
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Nov 29, 2011 | 09:28 AM
  #5  
From continued searching I've found the TPS and oxygen sensors can cause random misfires. Do anyone have any other opinions. If my time would of jumped wouldnt I be getting a cel?
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Nov 29, 2011 | 12:30 PM
  #6  
hump de bump
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Nov 29, 2011 | 05:00 PM
  #7  
BUMP
mine's stumbling too.
idles around 400-500 and then drops down to 200 and back up in 500. really killer on acceleration
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Nov 29, 2011 | 05:38 PM
  #8  
Mine was having problems excellerating too until I changed plugs and injectors. Your idling describes mine to the t.
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Nov 29, 2011 | 05:39 PM
  #9  
Now I've read about cps being bad from the get go but could this be caused by say a bad cps
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Nov 29, 2011 | 06:22 PM
  #10  
Try testing resitance on your cps.... its such a PITA to get to but i may be the issue...

and i dont know about the newer XJS, but check your grounds.... it seems to be the reason for every problem ive had aside from one...
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Nov 29, 2011 | 06:35 PM
  #11  
A better test for the Ckp sensor is in millivolts. Unhook the plug and probe the sensor side. Have someone crank. Should be around .05. I would do a compression test.
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Nov 29, 2011 | 06:52 PM
  #12  
I've thought about doing a compression test but it's hard to believe this would just show up afterwords. Unless when my timing was off and somethig got screwed up in there. Is possible idk? If a lifter or valve did get screwed up would that even show on a compression test
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Nov 29, 2011 | 06:54 PM
  #13  
I'm not sure if I understand... Are you talking about valve timing?
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Nov 29, 2011 | 07:05 PM
  #14  
Yea I don't understand much myself lol. Let me rephrase that. Could a valve of got damaged with the timing being off before I adjusted the camshaft sensor that could possible be causing the mis. The compression side of that comment still makes no sense to me, not sure what I meant
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Dec 3, 2011 | 04:17 PM
  #15  
Today a check engine light came on. Tried to check the code using the selfcheck trick and nothing popped up on the odometer? Yet the light was on. Drove down to autozone and it shows p1391. So that brings me back to the timing chain jumping or the new cps is bad. It does test good but if it's intermittent it might not show up is my thinking. I don't know much about timing but would a chain jump cause this or a bad cps most likely
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