2000 XJ Cruise Control Problem

My cruise control on my Cherokee is starting to act up. I will not hold any speed over 60. If you set it at 70 it will fall back to just above 60. Is this a vaccum line or canister problem? If so, how do I fix it?

Thanks!

I have this same problem anyone else? I will set it but then it falls back to 50-55 and kinda holds but not well on hills. Any ideas guys? I have been searching this for some time and seen nothing on it.

Oh yeah and mines a 90'