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I have an 89 2x4 4 cylinder manual and has driven fine until i took it in to get mu muffler repaired and a shop, since then it stalls after slowing to a stop and super poor gas mileage, also shakes at idle.

 

yesterday now i traveled to a town south of me, got there fine but had to fill up and figured i only got 8mpg, then i tried to get back on the highway and the truck shook and stuttered so bad that i couldnt get it past 45mph even if i had it floored and then once i limped it to a safe place it wouldnt start for over an hour and continued the same problems. i have no clue where to start looking for problems. any advice would be appreciated

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Just for clarification, it's not carburated. It has throttle body injection, with a single injector in the throttle body.

 

Do a basic tune up (plugs/cap/wires), and check your fuel pressure. Could be a dying pump, clogged filter, or shot regulator.

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Thank you for the clarification, i hate sounding like an idiot when it comes to my own vehichle. i thought it didnt look like a carb and still learning the comanche engine.

 

Anyways, I had it looked at today and mechanic said cylinder 1 is dead with only 30 psi. Put brand new bosh platinums in it with wires this past august and the plug was completly shot. Said when they put a new plug in it, it rarely fired. I did however see that the O2 sensor was in and not loose at all, dunno about the cat though. Did notice the last time i had it running that black flakes would shoot out into the snow from the exhaust. Also vacuum hoses keep poping outta place, specifically the one coming outta the valve cover in to the throttle body.

 

Thoughts about what to do next before i tear apart the block? or just drop a new engine in?

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I'd pop the head off before yanking the motor, may just be a head gasket. I'd had that hope with my 2.5... but when I got the head off, it turns out a ring had let loose in cylinder #1 and gouged the living hell out of the cylinder wall.

 

Might be easier to just dump a used motor in, but also may be harder to sell.

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Meant to elaborate on my answer but got interrupted. Not knowing what all the shop replaced but all the symptoms sounds like a clogged exhaust. Did ya ever shove a potato up any ones exhaust? Does exactly what you're describing. A couple years back a guy took his car in for a new muffler. He had been messing around with guys sister who installed the new muffler. The guy stuffs an apple in the muffler B4 installing it. After many days of frustration, and dollars spent on trouble shooting, the apple finally dried up and got blown out the tail pipe, destroying any evidence of vandalism. Start the engine. feel the muffler and or the tail plpe. It should get hot at the down pipe first and the heat should gradually move back to the end of the muffler. If the front of the muffler, or pipe, gets hot and the outlet doesn't, then it's clogged. That shouldn't be the cause of the low No 1 cylinder but what the heck. Just a thought.

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Well i have whored myself out around here... sooo that wouldnt be any surprise to me. As for resale, I'm not too worried, i usually drive my stuff till its beyond fixing anyways. Plus i don't think i would sell this truck too soon, I mean its a god damn comanche.

 

Appreciate all the help though!

 

Curious though as to since this engine could be getting worked on and going by it just being a 2x4, what would be some upgrades that you guys consider with your trucks?

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Do the xjs use the same engine or are they a 6 and still compatible? also what years of the xj will work?

An MJ is essentially identical to an XJ in front of the doors. You might even be able to find one from the same year with the same engine as yours but runs better. If it's a six cylinder, you can swap that in, too. Anything after 91 uses a different electrical system, which would complicate things, but it's been done. Post 96 goes to OBDII, complicating things more, but again, it's been done. Either way, you should be able to find a write-up on here somewhere.

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Anything after 91 uses a different electrical system, which would complicate things, but it's been done.

 

Be aware also that if you have a manual, 91 and up 4.0s use a different pilot bearing that WILL NOT will not work with pre 91 AX15s, ask me how i know this.

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