So i have an 89 and it was running fine. When you cold start it runs fine, even drives. As soon as it reaches a sertain temperature (?) it bogs out and runs horribly. It runs fine at first which makes me think the engine is fine but something is changing when the temp hits whatever and it stops running. ANy help is welcome, i need to fix this asap

what size motor
i had the same problem with my '93 4.0L turned out to be my cat was starting to clog up