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Unread 10-31-2009, 07:38 PM   #1
goul6891
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2006 LJ Wrangler 
 
Join Date: May 2009
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97 4.0 misfire on #1

Cylinder #1(closest to radiator) refuses to fire at all. I picked up this rig in non-running condition. Just finished replacing the head gasket, lapping the valves in, everything in the valvetrain is good, and the cylinders all looked fine. Put it together and it failed to idle on its own and sluggish throughout the RPM range. Replaced the IAC and TPS and it helped the idle problem. By pulling injector wires while running, #1 seemed to make no difference plugged in or not. Pulled the fuel rail, injector 1 didnt look like it has been injecting much(all crusty and carboned up on the nozzle, all the others were fine). Put a remanufactured injector in and still running rough. Thinking it may be an ignition problem, put new wires on and replaced the cap and rotor(they were oxidized kind of rusted). It still is only running on 5 cylinders I'm running out of ideas.

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Unread 11-01-2009, 11:19 AM   #2
ZeeJay1997
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1997 ZJ 
 
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Quote:
Originally Posted by goul6891 View Post
By pulling injector wires while running, #1 seemed to make no difference plugged in or not.
Don't place too much confidence in this because as one injector drops off the others throw more fuel. Its hard to tell a difference on mine. Do you get a CEL when you pull it?

Other things to consider:
the cam sensor (in the dist)
crank (on bell housing) sensor.
low voltage from the ASD relay or a shorted o2 sensor (unplug them)
pulse signal (low side) from the PCM is shorted out somewhere (middle PCM plug, terminal 4).

You also may want to take the inspection cover off the bell housing, rotate the crank and see if any teeth are missing or damaged in the 3 sets of four notches.

HTH
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Unread 11-04-2009, 09:36 PM   #3
goul6891
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i feel dumb about this one. i put plug 1 in the head(thinking it would be hard to get at otherwise) before setting it on the block. not such a good idea. pulled the spark plug to do a compression test and sure enough, the electrode gap was nonexistent. regapped it and now she purrs like a kitten. moral of the story-keep the spark plugs out when installing the head.
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Unread 11-05-2009, 04:10 AM   #4
ZeeJay1997
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Ah, the old KISS theory.
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