I have a 1989 Chevy Cheyenne C1500, it has a 4.3L V6, 2WD, Manual Transmission. The truck has been sitting for about a year, and it was running fine before it sat. I start the truck and it starts right up but stalls immediately. When it stalls it doesn't make any sounds just sounds like the engine was turned off. If i start it I can pump the gas to keep the engine going but as soon as I stop pumping the gas it stalls out, when it stalls out like this the engine stutters than dies like it is running out of gas. While pumping the gas pedal to keep the engine running when I push down the gas pedal nothing happens, but when I let off the gas pedal the engine revs. I have replaced the Fuel Filter, the Oxygen Sensor and the Throttle Position Sensor, with no change in the problem. I have tested the TPS connector with a voltmeter without the TPS connected and it reads at about 5v, which according to the manual is where it should be. I have tested the new TPS and with the throttle closed it is at .6V and goes to 4.4V when fully open, which again is what my repair manual says is normal. I have put new gas in the truck. I have taken off the Air Intake Assembly and watched the fuel injectors in the TBI while a helper keeps the engine running and it looks like the fuel injectors are working just fine. I am a decently capable backyard mechanic and can fix most things when I figure out what needs to be fixed, my trouble has always been in trouble shooting the problem.