Cruise control wont maintain set speed

97 GC laredo 4.0
When i set cruise it very slowly creeps up in speed and next thing i know im doing 5mph faster than set speed.....and will keep going if i let it eventually i have to hit the cancel or decel button
Where should i start looking?

That makes me think that the PCM thinks you have less vacuum than you actually have. Possibly there's a MAP sensor and there's a leak in it's line. That'd likely be a small enough orifice to only affect the specific sensor. Then the PCM would be trying to pull more on the cruise diaphragm than what's needed.

I could be wrong. Just a thought!

Thought about that....ill dig out my mityvac gauge and see what i can find.