94 century vibration under load

I just bought a 94 century for $300. It runs pretty well, but I get a kind of vibration/shutter when going uphill and stepping on the gas pretty good. (under load) It accelertes ok, but this small quick shutters are very noticeable. It is a 3.1 engine with 182k miles on the car. It's very drivable, but just a little annoying Any suggestions?

if it hasn't been tuned up in a while (plugs, wires, PCV, and fuel filter) try those first. It's routine maintenance, and wouldn't be money wasted even if it doesn't cure the shudder. The other common cause of a shudder under load at highway speeds (above 40mph) is a sticking TCC solenoid in the trans. The TCC controls torque converter lock-up, and when they go bad, the symptom is similar to trying to accelerate in a stick shift car from too high a gear for the speed you're traveling.