2.3L ('83-'97) Truck idles rough

[832.3ranger]

I have a 1988 2.3 with a wiring harness from a 1986 2.9 that’s modified a few ways to make work for the 2.3 and recently I used a stud puller on it and fried the 1988 2.3 computer then put a 1986 mustang 2.3 computer in it and now it runs fine to start up but once it warms up it does a low idle and stumbles and then after about 15 or 20 seconds it’s straightens out again and will run fine for as long as you don’t turn it off. But then when you turn it off and back on so it’s still warm it will do it still. Any help would be appreciated I hate wasting the gas letting it warm up on days that it’s warm out. Thank you!

 

[franklin2]

What codes does it have?

 

[SenorNoob]

Was the Mustang computer from a manual?

 

[832.3ranger]

Was the Mustang computer from a manual?

Yeah the guy I got it from said it was it only does it once after it warms up and then runs fine till you turn it off and on again

 

[832.3ranger]

What codes does it have?

I think it has a evap code. And there’s a coolant temp sensor out to range code and then the power steering code because the mustang had power steering but my truck doesnt. The rest of the codes is just stuff the truck doesn’t have but the mustang did

 

[franklin2]

Coolant code may be something to zero in on. All I know, from experimentation if I unplug the coolant sensor on a EECIV engine that is sitting there running, it will stall as soon as I unplug it. So it must be a pretty important sensor.