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88 MJ idle issues,.. Seems like a miss 2.5L


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Ok I scored up MJ number three but this one I get to drive!!! Once I swapped a starter and alternator into it,..

 

So that being said the idle sucks,.. Fire it up and it's ok(ish) not great but ok,.. Now drive it for 5 mins and it shutters and slightly recovers but shakes like a dog s#itting razor blades. Of course I put a tank of premium fuel in it, injector cleaner, tune up bits and it seems to be better,.. But not correct. I am leaning to swapping in a new o2 sensor next but have little experience with 2.5L tech

 

When drubbing everything feels good and smooth with the occasional momentary "flat spot" like an old carb set up,.. Power,.. Well it's a 2.5 won't wow you but can get out of its own way,..

 

Next steps? Oh it's a 88 with 163,000 Kms stored 7 years

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The 2.5 is notorious for oil leaks from the plastic valve cover , down the bell housing and into the opening for the ESS ( aka : crank sensor ) which is also has vunerable wires running very close the exhaust . ( Melted insulation ) Often pulling the sensor , cleaning it and the wire connector block will cure the problem . ( also a nomex sleeve over the wires is a good preventive mod ) While your at it , check all the grounds , Firewall to block , cluster at dip-stick bracket to block , battery . This should ensure the ECU is receiving reliable info & fire consistently . :cheers:

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The 2.5 is notorious for oil leaks from the plastic valve cover , down the bell housing and into the opening for the ESS ( aka : crank sensor ) which is also has vunerable wires running very close the exhaust . ( Melted insulation ) Often pulling the sensor , cleaning it and the wire connector block will cure the problem . ( also a nomex sleeve over the wires is a good preventive mod ) :cheers:

 

 

Funny you mentioned valve cover,.. As mine is leaking and by the looks of it for some some time,.. I planned on doin it on the weekend. Now maybe sooner than that. I will report back!

 

Thanks!!

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The 02 sensor can cause that as well. Mine ran similar to yours after I got it going. I did all the same tune up stuff with only marginal improvement. I put the O2 sensor in and its been great ever since. Mine was also stored for a long time rarely being driven, though the PO did try. Let us know what you figure out.

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Well the stutter is back at intersections,.. feels like its going to stall but recovers to a miss at idle,... grrrr

 

So far cap, rotor, wires, 02 sensor, TBI cleaning, tank-o-premium and injector (tank) cleaner,..

 

Neeeeext? :thwak:

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  • 3 weeks later...

my '87 2.5 's been doing the same thing ... after tuning it up (which didn't help ) swapped out coil's , map sensor cps was replaced before , just completely baffled ... :???: :dunno: truck will run fine for many miles then outta the blue start bucking , sputtering like it gonna die then clear up ... after spending most of the weekend "working" on it (and pulling my hair out !) i sprayed the tb with crc cleaner ( looks better anyway ) changing out cap and rotor (3rd time) no differance ! suddenly i noticed it began to idle very high ... got home to find a large vacuum hose had come off at the base of the tb ... replaced several lines with new hose , started it up , idle ... fine ! took for yet another ride ... PERFECT ! spoke too soon , started the same sputtering , bucking ! I COULDN'T BELIEVE IT !!!! got back and checked all again ... nothing outta the ordinary . with it barely running , for some reason i decided to unplug the tps , GUESS WHAT ? it "cleared" right up took the ol'boy for another ride , seems ok ! i'm going drive it a while to see if it starts acting up again , but i think i've finally found the problem the DAMM TPS !!!

comanche.gif :banana:

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my '87 2.5 's been doing the same thing ... after tuning it up (which didn't help ) swapped out coil's , map sensor cps was replaced before , just completely baffled ... :???: :dunno: truck will run fine for many miles then outta the blue start bucking , sputtering like it gonna die then clear up ... after spending most of the weekend "working" on it (and pulling my hair out !) i sprayed the tb with crc cleaner ( looks better anyway ) changing out cap and rotor (3rd time) no differance ! suddenly i noticed it began to idle very high ... got home to find a large vacuum hose had come off at the base of the tb ... replaced several lines with new hose , started it up , idle ... fine ! took for yet another ride ... PERFECT ! spoke too soon , started the same sputtering , bucking ! I COULDN'T BELIEVE IT !!!! got back and checked all again ... nothing outta the ordinary . with it barely running , for some reason i decided to unplug the tps , GUESS WHAT ? it "cleared" right up took the ol'boy for another ride , seems ok ! i'm going drive it a while to see if it starts acting up again , but i think i've finally found the problem the DAMM TPS !!!

comanche.gif :banana:

 

That's what I was thinking of suggesting to the OP. Those vac hoses near the TB are notorious for rotting and causing all sorts of problems. I bought an 86 MJ because a guy couldn't figure it out and just wanted to dump it. When I went to pick it up, I brought some vac line. Installed it, started the Jeep and drove away.

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