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94 xj 4.0 high output misfiring

Old 04-21-2019, 11:20 AM
  #1  
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Join Date: May 2018
Location: Indiana
Posts: 69
Year: 1994
Model: Cherokee (XJ)
Engine: 4.0 I6 H.O.
Default 94 xj 4.0 high output misfiring

I have fixed all vaccum leaks.
Replaced spark plugs with oe champions gapped properly.
Accel cap and rotor.
Prestolite plug wires
703 dodge neon injectors
New oxygen sensor with headers and new exhaust
New map sensor
Fuel filter and fuel lines
Oil does not smell like fuel is in it
Rockers are torqued properly
I have not checked fuel pressure or done a compression test.
The obd1 code that is set off is 27
When i try to check the voltage on the injector wires i do not get a proper reading with my snapoff multimeter. Not sure why they are the 2 prong connectors.
Have yet to replace air intake
I just put the 703 injectors in last night they used to have the 749s which are for newer models
I disconnected the battery flashed the pcm still have the code.
It starts nearly instantly now and it idles around 900 goes up to about 1000 and you can feel the misfire it drops down and brings it back up.
Have yet to change air filter its all stock
the pcv/ccv is all replaced new.
Cleaned throttle body have not replaced the iac.
It gets to 210 degrees when sitting still if i drive it goes way down.
I have not replaced ignition coil
Oil changed every 3000
New oil pan gasket rear main seal and valve cover gasket.
New battery cables and fixed so much electrical
New oil pressure sensor
Almost completely new cooling system
New power steering pump and lines i know this stuff is getting irrelevant but trying to be thorough.
If i need to get oe injectors i will try it.
I was considering doing that and replacing the cap and rotor with mopar get rid of the accel.
If anyone has any tips or ideas please let me know
I never want to part with this i have rebuilt it interior and exterior besides tearing down the block.
Its at 234000 miles. I will in time get a new block and then i will turn it into carb instead of efi.
Thank you all!
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Old 04-21-2019, 02:21 PM
  #2  
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Location: Indiana
Posts: 69
Year: 1994
Model: Cherokee (XJ)
Engine: 4.0 I6 H.O.
Default

So far i have used an infrared thermometer cylinder 1 and 6 are about 225 degrees fluctuating. 2-4 are fluctuating around 98-138 degrees

Added later.... The pcm casing is cracked missing a corner i plan to test its pins ill update when i do

Later in the day. I did a voltage test on each injector wire terminal. All were ablut 14.8 except cylinder 2 which was at about 500mv. The wire looks like garbage replace the pigtail and see from there if not ill trace it back further

Last edited by Romans715; 04-21-2019 at 08:23 PM.
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Old 04-26-2019, 02:44 PM
  #3  
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Join Date: May 2018
Location: Indiana
Posts: 69
Year: 1994
Model: Cherokee (XJ)
Engine: 4.0 I6 H.O.
Default

Ok so now i have fixed #2 injector wire terminal.
It is reading the same voltage as the rest.
Still have obd1 code #27 going off.
Can still feel the misfire but it doesnt seem as bad.
When i use stethoscopes they all click except for the one i fixed.
Like a constant click click click almost how the engine sounds i do not know if i was listening for the correct sound. But that one does not sound like the rest.
Use an infared thermometer it reads about 110 degrees while the rest are higher i dont remember off the top of my head.
Any ideas? I am dreading replacing the pcm if it comes to it since i can not find one for a 1994 automatic xj 4.0 besides ebay i can give the part number if anyone asks. I know the last digits are 888
I do not know if i can use another years pcm. I have looked it up but no results.
I was thinking maybe replace my champion spark plugs again since that one may be all kinds of funky not firing but yet to pull it and see its condition.
Considering replacing the cap and rotor for mopar and get rid of the accell.
Maybe replace the iac and ignition coil?
Im not sure. Going to see if any more grounds need cleaned up.
Im not sure im trying my best here
Still yet to buy a fuel pressure gauge.
I dont remember if i said it before but i spent 2 years rebuilding this interior and exterior whoever had it before me really did a number on all electricals and body it was junk before i have restored so much on it
I will not get rid of it i love this Jeep more than any other vehicle on the road. Just want a wrangler sport for a secondary vehicle in case this one is down for a few days.
Well thank you all for any help that you can give!
Have a wonderful day i just cleaned up my tools and planning to take my girlfriend out for wings and a beer tonight
In the meantime i will be doing more studying!!!
This thing is always testing me. XD
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