1990 Comanche 4.0 auto misfire @1700rpm??

About to pick up a 1990 comanche with a 4.0 auto in it but am leary as it has a slight misfire at 1700rpm. The engine was just rebuilt by an actual machine shop so its not a garage build. The engine was bored out .020", oversized pistons, new rods, has cleggs stage 1 cam and cleggs stage 2 head. The engine has maybe 50 miles on it after the rebuild so its still in its break in period. Am wondering before i get this, what might the general causes be? Would like to know how little or big of an issue it might be.

Edit: When i went and looked at the truck the engine would only misfire once. Owner says its a crap shoot on if it will happen or not any given day

I hope you got it this...pics?

POSJ said:

I hope you got it this...pics?

Click to expand...

It's a bit rough around the edges. I'm in college right now and do a co-op program so 6 months out of the year i have nothing to do once i get home. This is going to be my resto project for the next year or two. Going to spend a lot of time fixing any and all rust spots, sand down the body panels, add body filler where needed and get it all primered. Once it's already to be painted i have a friend with a paint booth and will do a good job on it. Like i said, its rough and going to need some work but its right up my ally and i view it as my diamond in the rough.



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I'd drive it, good find.

check the TPS sweep with an analog guage.
I bet you find a dead spot.
renix goes fuel cut when it thinks you've let off the throttle. A slight dead spot in the TPS (usualy around cruising throttle) will make it go fuel cut in the midst of acceleration, because that's what the computer saw.

If that's not it then it's probably just a simple ignition system problem.