I've got a 2000 Blazer that has terrible acceleration when the vehicle is cold and has been sitting overnight. Cruising at speed is okay with a bit of jerking, hesitation and cutting out and picking back up. Once warmed up it seems to be alright. The really baffling part to me is that after sitting for 2 plus hours and starting out again with a "cold" engine (as indicated on temp gauge) the hesitation and cutting out has vanished. Recently passed CA smog with flying colors (always has) and CEL isn't illuminating. I've changed fuel filter, cleaned EGR valve and checked plug wires to be sure still secure to plugs (plugs, wires, cap and rotor replaced 1 year ago). I haven't checked fuel pressure since the vehicle does in fact idle and run. Fuel mileage is right on, too. I even thought perhaps something in the transmission but when idling (in park) I can gently rev up and get the cutting in and out, jerkiness etc. I'm thinking some sensor is faulty when cold and okay once up and running but again once the engine cools down (and all the sensors should be at a theoretical cold setting) it starts up again every thing seems okay. I've wondered about a possible bad cylinder yet there's no oil in water or water in oil. My Haynes manual has some suggestions (fuel pressure regulator, throttle position sensor) but I'm at a loss.

 

Could be the IACV (Idle Air Control Valve)....