2001 Chevy Monte Carlo Passing cars

When on the road and wanting to pass a car, I step on the gas and instead of going to the next lower gear, it goes two gears down, without enough power to make the pass. There appears to be a rev limiter on the engine, because it maxes out at 4000. The 'check engine' light goes on briefly, then goes out. I put a CarMD on it, and no codes are generated.

I want to sell the car, but this problem will make it unsellable. Any advice?

Thanks,
Mike