I have a 1999 Chevy Blazer, 4x4, 4.3 vortec. We have changed the coil pack, fuel filter, distributor cap and button, the crank shaft sensor, cam sensor and plug wires as well as the ignition control module. We coming to a stop sign it will stall and sometimes when just sitting still. Sometimes it will start right back up and other times it takes several tries. I also have the oxygen sensor on order and it should be here tomorrow. Fuel pressure tested perfectly. No black smoke, no smell of rotten eggs or the cat glowing red. The only code that comes up is PO420.

Clean the throttle body good with CRC cleaner, there is a little hole in the flap that gets clogged. That hole lets air in when the car idling or at low speeds. Spray and clean the return spring as well...

Ok we took the throttle body off and cleaned it real good including the spring with throttle body cleaner. We then took the battery cable off for about 30 minutes so it could reset. The check engine light is no longer on but it just did the same thing. It died at a stop light and took several tried to start back up. We also filled up the gas tank and put fuel injector cleaner in it. We could see part of the spider injectors when we took the throttle body off and they look great.