I have a 2000 silverado, 5.3, that won't accelerate properly after startup, and doesnt throw any codes, it has me baffled. Starts up great, idles fine (no miss), revs fine in P, but it hesitates/stumbles terribly, and doesnt want to shift correctly until 50 mph, and after that it runs fine, once it does that I can stop and accelerate fine through all rpm's. But once I shut it off, it does it all over again. Also fuel gauge is irratic, as in it drops to no fuel and then climbs again to proper level, or vehicle is shut off for awhile and it will read half full until you open the door, then it shoots to empty.

I have replaced plugs and wires, ohm'd the coil packs and are in proper range, hooked up fuel gauge and reads roughly 48 psi at idle, and climbs to 60 psi as pedal is depressed, holds psi at 48-50 after shut off, newish fuel filter, cleaned the MAF. I'm leaning towards replacing fuel pump next but it confuses me that it works fine after hitting a certain mph, then back to problems after shutting off, restarting. I dont want to throw $200-300 into it and not have it fix it. Any suggestions?

 

I believe the sending unit, and pump are one unit. There was a recall on 2000 full size (my suburban fell under that) for fuel pump issues. It was a wiring issue in the pump.