1991 K5 surging problem

[OSDCrusher]

My 1991 K5 Blazer has a very bad surging problem. It surges especially bad when the engine is cold. When the engine is warm it doesn't surge as bad but you can still tell it is not running right. The exhaust smells rich. If you try to drive the truck while it's surging, it will buck violently and idle extremely low, it feels like it's going to stall out at any moment. If I unplug the coolant temperature sensor and try to run the truck, it seems to run a little better when the engine is warm. The previous owner tells me he replaced the coolant temperature sensor (doesn't look all that new) and wiring harness for CTS. O2 sensor (doesn't look all that new, plug wires (look new), fuel pump (verified new), throttle body base gasket (can't tell for sure if it's new), I.A.C. valve (doesn't look all that new), T.P.S. (doesn't really look new but I don't think this has anything to do with the problem). The transmission was rebuilt with a new torque converter. Any insight on this problem would be appreciated.