Cruise control failure. Replaced with known good unit. Still not working. Now what?

[LEGACY_GN]

Comes on briefly and starts pushing throttle before cutting off and then won't come back on till next time I start it. Must be sensor reading or something not reading right and causing ecm to shut off cruise control. What all sensors does cruise control use to run and what could be sending error causing ecm to disengage it?

Actually worked one night last month all the way home. But that's it for past year. Replaced today with known good unit and no improvement.

 

[HighMileage]

A common problem with that era GM cruise control is the wiring that comes out of the turn signal stalk. The wires exit the stalk before the hole in the column. The wires,which are tiny,chaffe on the opening in the column. Reach behind the stalk and you'll feel the wires.

One of my GM's is having an intermittent cruise issue right now. I reach behind the stalk with my fingers and try to feed the wires back up into the head. That will work for a while.

Had a bad vacuum servo on my GN when I got it. Replaced it with one off my '90 Olds Ciera's. Direct bolt on. That doesn't sound like your problem.

The next time it quits,try pulling up on the brake pedal with your foot. The switch down there might need to be adjusted.

Having 4 GM's of the same era on the road right now,all of which I use the Cruise,keeps me hopping in the Cruise repair department. Right now,they are all working. (knock on wood)

Turn your key to ACC and turn the cruise on and off. You should hear a fairly loud click coming from the servo.

 

[87geeinn]

Vacuum leak maybe? Chase all the hoses, especially the one that runs down into the car and up near the brake pedal. Also, is the check valve installed so you don't send boost to the servo?