I have an 86 jeep cherokee chief. it has a 2.5l 4cyl and i did an engine swap with another 2.5 out of a comache, i changed over all of my components such as the intake exhaust and all accesories and vacuum lines. i tried to start it and it runs but it cuts in and out and dies after about 15 seconds, i have no clue what to do ive tried switching vacuum lines and nothing has worked out, it has good spark and has plenty of fuel in the tank and gets fuel to throttle body. Any suggestions?

 

What did you use from the comanche,just the longblock?and what year was the comanche.

 

Yes, we used the long block and swapped out all the sensors and used the Cherokee wiring and intake. The Comanche was an 87.

 

I am not that familiar with the 2.5 as the 4.0 but there should be somwhere to check actual fuel pressure,i would hook up a pressure tester (if you have not already)and see if the fuel pressure is normal before starting and while it is running,it sounds like it is running out of fuel.
try that and go from there.

 

it has good fuel pressure but it runs and cuts out and runs and cuts out then just dies, but when it does run it runs really good

 

Sounds like a fuel issue.

 

Have you check the pressure with a guage?it can appear to have good pressure and be low. It sounds like it is starving for fuel.

 

but it ran when vacuum lines were messed up but missed out at idle and if you reved it up just a little then would clear out

 

If I am reading this correct it will not idle but if you hold the rpms up it will smooth out and run normal,correct? if that is the case then it sounds like a vacuum leak,if you can keep it running long enough you can spray some starting fluid around the intake and vacuum lines,if the idle goes up or becomes erractic then you have a vacuum leak,you can also get a vacuum guage and check it that way,should be around 15",if it is a vacuum leak then it will still stumble even at higher rpms. need to also go over everything again to make sure all is hooked up correct.
it can also still be a fuel issue,that is why I asked if the fuel pressure was the same at all times when running.

 

Got it fixed. Turned out to be a fuel issue. Thanks for the advice. The screw underneath the TBI connector was bottomed out, so I turned it back a little and it started running great. I think it's the fuel pressure regulator adjuster.

 

Thanks for the update,glad you got it fixed.

 

yup still seems like a turd tho, must just be me because im used to driving a v8 diesel

 

Yep,mine seems like a dog in comparison to my 72 chevy truck,but I love the versatilty of my jeep.