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random misfire 96 xj

88-cherokee

88-cherokee

NAXJA Forum User
Location
sac,ca
i have a 96 xj 4x4 auto 4.0 now i understand there's other forums open on this topic but my issue might be alittle different.
So my issue is at an idle i have a misfire on cylinder 1 and 1 only, ive pulled the header and welded the leaks cleaned the intake and tb. now heres a list of parts ive changed iac, tps, upstream 02 sen (cap ,rotor ,plugs and wires twice ). ive swapped around injectors, i even got a noid light to test the injector wires and everything checks out good but im continuing to have the misfire on cyl 1 only in not trying to hasta but im seriously not understanding why in having this issue
 
Burned valve from cracked header maybe? Run a compression test on all cylinders and get back to us with the results. Could also be a bad injecter or injector wiring.
 
I forgot to mention the compression test the numbers are as follows cyl 1 - 145psi 2-150 3-165 4-160 5-160 6 145 .
ive already moved injectors around and ill try tightening the intake and exhaust again.
Ill do the minimum airflow test as best I can as i don't know what program they are using in the video
 
So one of the points of the video is that you don't need the scan tool to do a minimum air flow test. You should see a rpm drop but the engine should still idle. The heads up data was shown to help the viewer "see" what the Ecu was doing.
 
Ok so i haven't done the minimum air flow test yet.
i was wondering if a crack in the header right at the number one cyl would cause the misfire im having?
 
The crack will affect the o2 sensor if its bad enough. Try spraying some carb clean around the intake when the engine is cold and running. If it starts choking or speeds up you found the problem
 
Very good power puts me in the seat. Once I get the rpms to about 900 and up i can't hear the misfire. Also none of the monitors are setting the ones needed to pass smog

Edit: would it hurt to swap computers from my dd to the one with the misfire and see if it follows the computer?
 
So i did a leak down test and everything is tight checked my distributor and its good. i think ive narrowed it down to a corroded injector wire that isn't alowing enough current to open the injector on cylinder 1 im going to order a new pigtail and go from there when I get it. I swapped pcms and the problem didn't follow so i think im safe to say its the pigtail. ill update as to if it fixed it
 
If the new plug dosen't fix it, the trouble is almost
certainly a sticking #1 injector. I had this same problem
with a (cough)Explorer last winter.
 
Runnin'OnEmpty said:
If the new plug dosen't fix it, the trouble is almost
certainly a sticking #1 injector. I had this same problem
with a (cough)Explorer last winter.
Click to expand...

Ive moved injectors around multiple times without the problem following and if its not the plug. My next guess would be a bent rod
 
update on my jeep im going to have to pull the head and check the valves its the only thing left to do now. I changed the plug and it smoothed it out some but i still have a misfire. If anyone has any input on what they think i should do please let me know. Any help is much appreciated.
 
Your compression numbers and leak-down testing
shows nothing wrong inside the engine. I wouldn't
remove the head just yet.

You said you checked the distributor, but there might
be a problem that's not apparent. I'm thinking specifically
the number 1 terminal inside the cap. A borderline ignition
issue will show up first at idle speed, rather than at higher
rpms; that makes me suspect it's ignition related.

I'd replace the cap and rotor as the next step, even if
the cap looks good.
 
Runnin'OnEmpty said:
Your compression numbers and leak-down testing
shows nothing wrong inside the engine. I wouldn't
remove the head just yet.

You said you checked the distributor, but there might
be a problem that's not apparent. I'm thinking specifically
the number 1 terminal inside the cap. A borderline ignition
issue will show up first at idle speed, rather than at higher
rpms; that makes me suspect it's ignition related.

I'd replace the cap and rotor as the next step, even if
the cap looks good.
Click to expand...


but ive replaced the cap, rotor, plugs ,and wires twice you really think its bad? Do you think it might be the distributor? I might just build a 4.2 out of it i havent decided yet. I will check the ignition again and see what i can come up with.
 
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