My 1987 jeep cherokee dies after running for a few minutes, I've changed the ecm, the coil and the starter and battery what do I do next?

It may be the fuel pump is going bad or the fuel filter dirty and needs changed. Also have you checked the catalytic converter to see if that is clogged?

Only use the same Champion spark plugs that originally came in the vehicle. No cross-reference plugs. If the problem persists, focus on the Ignition Control Module--they frequently fail.