02 Grand Marquus won't accelerate
 

Hi everyone, last summer I bought an 02 Grand Marquis that now has 104k miles on it. The guy I bought it from said that the trasnsmission had went out and he rebuilt it at about 80 k. Idon't have any details about why it went bad or how it was rebuilt. Anyway, the car runs great and accelerates normally, actually rather quickly at speeds up to about 50 mph. Once cruising at highway speeds, it refuses to accerate any faster. Even if I mash the gas, absolutely no response with the pedal bottomed out on the floor. Then, all of a sudden it realizes it and powers forward. I need to add, this issue doesn't seem to happen every time, but definetly frequently enough. Also, many times this occurs when traveling up a slight hill. If the car has momentum, it effortlessly cruises to 70+ mph but once I'm coasting at steady speed it wont budge. Any insight or advice is much needed and appreciated

I would suspect the transmission.

Try disengaging the OD and see if the problem remains.