Northstar Engines and System Technical Discussion Discussion, cruise control not working properly! in Cadillac Engine Technical Discussion; w/cruise set it won't accelarate w/accel button,and when going up hill let's say at 70 mph it backs down to ...
OBD I will doubtfuly throw any codes for cruise control.
Find the servo under the hood, and check for good strong vacuum from each of the vacuum lines while the engine is running.
If you don't suspect any vacuum leaks, then I would look at servo replacement.
I don't know how to test one, maybe someone else can give a little heads up on that.
I know in my dad's delta 88 work car, its gone through a few in its 200k mile lifespan.