I have a 1998 Civic LX with cruise control that has never worked in the 50,000 miles since I've owned it (it now has 110,000 miles). When I engage it while going a steady, say 65mph, it stays steady for a minute, then the car thrusts forward and will accelerate a few mph, go back down to 66, then up to 70, back down then the cruise thrusts up again. It may eventually get up to 75mph and will always back down a few and thrust upward again.

This happens on even and hilly roads. The car really thrusts forward like I threw the hammer down. Also, if I try to disengage the cruise, especially if it is accelerating, it ignores the fact that it has been turned off! Even if I turn off the cruise switch and step on the break, the car still pulls forward. It will stop after 10 seconds or so, but it can be dangerous. Also, if I step on the clutch while this is happening, the engine will red line.

Thanks for your input!!
Boysterload
www.powunclehal.com

 

Sounds like you have a vacuum leak. There should be two vacuum lines to look at first. The first one goes from you intake mani to the CC unit. THe second goes from the CC unit somewhere else. Check those for leaks, cracks, holes. At least that is my best guess.