missing at 55 mph - 99 Sebring

I have a 99 sebring. When I am traveling at about 55 mph, the vehicle starts to miss as I try to pass someone.

As I step on the gas to pass, the vehicle stays at about 55mph.

Any ideas?

this happened to my dads sebring. check the transmission torque converter and have a tune up done if you havent lately. seems this car has fuel and driveline problems, among others unfortunately. it could be a costly repair. we had to replace the transmission($3,000) as well as numerous other parts at least ($2,000) and it still doesnt run right.