I have a 01 Blazer, 4.3, all wheel drive, Auto, 80K. The trans was rebuilt a year ago.

I have a hesitation at crusising speed and accelaration. At a constant speed the car hesitates, bucks etc. It idles great and runs great other than that.

I'm running out of ideas. I have recently replaced Plugs, wires, dist cap and rotor, and the crank pos. sensor. Ran Seafoam through the gas.

I know it's hard to diagnose over the internet, but anyone have any idea? Oh, no codes. No check engine lights.

 

Maybe the catalytic converter, knock on it see if it rattles or see if you have a sulfur smell in your exhaust.

 

SEAFOAM melted my Cat Converter in my 97 Blazer 4x4. It started running poorly at speed & I took it to a muffler shop & they found the converter melted inside. It wasn't long after running Seafoam in it.

 

Since you replaced the crank sensor maybe take it to the dealership to have them plug their computer into it to adjust the Crank / Cam sensor. "Case" relearn I think it's called.