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New XJ in the family need some help

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WesternRed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Topic: New XJ in the family need some help
    Posted: Apr/25/2018 at 7:41am
So I sold my SJ Cherokee a while ago and have just bought an XJ to fill the need for a Jeep in the family. The idea is that it be a first car for my young bloke, who is now old enough to drive and it is probably a bit more sensible than a 360 powered SJ.



I know it's a bit late model for die hard AMCers , but not straying too far and I'm sure there are some knowledgeable people on here. The issue is it has a pretty severe missfire, basically rough idle and under any sort of load. At light throttle cruise and free revving, it seems to run ok. Came with a few spare sensors, so previous owner has been fiddling to try and solve it, but has given up and hence it was a cheap purchase for me.

Just got it home, so haven't had much of a chance to tinker, but looking for some ides and diagnostic tips if anybody has some?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2018 at 8:54am
What year and engine?

I know they used Diesels in other parts of the world after they stopped using them here,
not sure if you guys got the gas 4.0L in the majority of them like we did in the US.
71 Javelin AMX P-code Go pac 360/4spd/3.91's
was Green/green now T/A red w/blk leather

88,89&98 Jeeps
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WesternRed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2018 at 6:39pm
Sorry, 1995 4.0 petrol engine with 4WD and auto transmission (gas means LPG down here).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JeeperJolene Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2018 at 6:46pm
Is it a random misfire or is it the same cylinder?Is it after the Jeep warms up, cold or both?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2018 at 7:07pm
Yeah,
 those 91-95 4.0L's will pretty much run great no matter how bad they are neglected.

Crank Position Sensor usually makes itself known by randomly not starting,
 injectors can get dirty like anything else,
 and a bad Throttle Position Sensor can hurt acceleration, or make the trans not want to kick down,
 but it's really one of the most simple MPI systems around.

The distributor is supposed to be locked, I wonder if someone tried to "adjust" is sometime in the last 23 years (?).
 A weak coil is possible,
 but I've had them all either work great, or completely fail with nothing in between.

I'm guessing you looked at the plugs, fuel filter, wires, etc?

Sometimes the throttle body can need a cleaning,
the little idle step motor in the TB (I forget the name right now) can clog and give it a bad idle

 and the thin CCV tube at the back of the valve cover clogs so the air filter fills with engine oil,
 but the CCV shouldn't hurt the idle much.

If that stuffs all good I think I'd peek to see no one messed with the distributor, then try a compression test to see what you're working with.
I guess a flat cam is a possibility too, but I've never run into that either.

 Great vehicles tho,
 good luck
71 Javelin AMX P-code Go pac 360/4spd/3.91's
was Green/green now T/A red w/blk leather

88,89&98 Jeeps
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jpnjim View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2018 at 7:14pm
I'll add one more thing,
 the simple plugs/wires/cap & rotor is the main thing with these,
 I had one run poorly for a while,
 after a tune up.

 I couldn't understand why,
 till I pulled the distributor cap and saw that the rotor was 50% missing LOL

I have no idea how it even ran with half a rotor, but that's how reliable these engines really are,
 they just *want* to run, no matter what Clap
71 Javelin AMX P-code Go pac 360/4spd/3.91's
was Green/green now T/A red w/blk leather

88,89&98 Jeeps
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amxdreamer Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2018 at 7:49pm
Great vehicle for a new driver. A little higher up so better visibility and collissions and can take a bit of a beating! This is my 16 year old sons that he has been slowly fixing up!

Tony
Vancouver, BC
1970 AMX
AMO#10333
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AMXRWB Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2018 at 10:43pm
Cracked head could be the problem.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2018 at 11:32pm
Lets hope not.
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WesternRed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2018 at 7:06am
Just did the key dance and the only OBD code to come up was 55, which pretty much means nothing wrong there.
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