So I have been having this problem on my 98 Z28 for a couple of months where when I am like accelerating at a low rpm around 50 mph the motor starts to buck and kind of lunge until I give it a little bit more gas and the tranny downshifts and then it stops hesitating and drives normal. I havent thought that much about it cause the engine hadnt yet thrown a code, until earlier this week the check engine light finally came on. I kind of figure that it is the 02 sensor or the fuel pump but Im not sure. I took it to Autozone so that they could run a diagnostic on it and tell me what tripped the code but they said it was a P1460 code, and that that is a manufacturer's code and that only the dealer could tell me what tripped it. I saw a link that showed what the cause for different codes and it says for P1460: DTC P1460 Cooling Fan Control System or DTC P1460 Misfire Detected With Low Fuel Level. I already replaced the fuel filter. Also sometimes after I have been driving for a while, I here like this high pitched humb coming from the rear end. I am almost positive that the noise is the fuel pump. But the noise isnt real consistent; it just kind of cycles on and off after a while. Has anyone here had similar problems or have any idea what is causing this?

 

It sounds like it went lean and misfired. I would guess that maybe your pump is having electrical problems (grounding issues), or maybe it's on its way out. How many miles are on your car?