I searched and there are quite a few cruise control topics but none that I foud to address this problem.

I can set the speed and it will climb up 5mph then lets off abruptly and then speeds up again. Any ideas as to why its doing this? Could it be cable slack? I adjust the trottle cable slack but its still doing it.

98 EX

 

Check your vaccum lines and cruise throttle cable.

 

Almost sounds like your cruise control buttons are malfunctioning or sticking. Maybe try taking them apart and cleaning them? The only other thing I can think of is a possible vacum leak maybe...