Chevrolet Repair: fuel ing., throttle position sensor, chevy 3500

Question
Hi I have a 93 chevy 3500 4x4 5sp with the 5.7L in it and It starts up and sounds like its choking to warm up and then it runs good for 3 or 4 min. then it starts the loud sucking sound like when it first starts missing and then black smoke comes out of the tail pipe until it finally floods out I have replaced the distributor,coil,plugs,wires,injectors,throttle position sensor, and is still doing it to codes aren't showing up belive to check engine light is bad any suggestions would be much appreciated.

Answer
The throttle body gaskets on those models have been prone to leak which may be causing this. Spray carb cleaner around the exterior of the throttle body to locate a leak.

You should also scan the PCM data stream to see where the fuel trim data is at.

I would also check fuel pressure.