My 99 Jimmy stalls but only after reaching running temperature and idling for 5 minutes if you are driving at highway speeds it doesn't stall at all it only acts up at low speeds or when stopped like something is getting hot.I have changed the high voltage coil the module and the distributor pick up coil and it holds 55 psi fuel pressure while idling and goes to about 60 when I rev the engine, and the fuel pump runs about 3 seconds after it stalls so I don't think it's fuel related but if I open the hood and it cools down for 10 minutes it will start and run again. Could it be as simple as a hot relay for the ECM? It never turned on the check engine light at all.
Get a helper disconnect a sparkplug wire or 2 and ground it to the engine atleast 3/16 away from ground-have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel related problem, Do you hear the fuel pump come On when you turn key on? If not check fuel pump fuse and fuel pump relay if okay-check the fuel pressure to rule out the fuel filter/fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light. No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil packs,coil's resistances,cap and rotor,distributor pick-up coil, ignition control module, cam and crank sensors and computer Note: If it doesn't apply disregard it and keep testing