sporadic cruise control

Year, model?

Most of the time it's a vacuum leak or a faulty solenoid.

Er..yeah, my bad. It's a '96 Grand 6 cyl Laredo

Check the brake switch, going off when you hit a bump might mean the switch is too touchy.

Thanks for the reply. I apologize for my ignorance but what/where is the brake switch and how to I check it?

If you look under the dash at the brake lever (part attached to the brake petal) you will see a little box with a plunger coming out of it that rests on the top side of the brake petal. There is a nut holding the switch that can be adjusted to allow more or less pressure on the switch. In the case of my '93 it is off when depressed fully. As you apply the brakes, the plunger comes further out lighting the stop lamps. It's a very touchy adjustment, and may require a new switch.

Dick

Dick proclaimed:

For the original poster, please keep enough of the old posting so someone can follow it.. for example, keep the 96 grand cherokee I-6 presumably with automatic trans in each post.

Does it have any trouble codes? This is the on-off-on-off-on of ignition in 5 seconds. Look for flashing Check Engine light.

A 55 is end of codes.

15 is the speed sensor input path, checked while vehicle is moving 34 is the speed control path with an open or short in speed vacuum sensor, vent solenoid sensor, speed control switch voltage low, speed control switch voltage high.

Disengaging, particularly on bumps is usually the stop lamp switch or speed control switch loose or misadjusted.

With the notoriously bad jeep grounds always on the table of choices.

The speed control switch may be best handled by someone familiar with the concepts of a live airbag going off in your face... the switch itself is held on by a couple screws from the back of the wheel. Just pull all leads from the battery and wait about 5 minutes first.

My CC was doing the exact same thing yours is. The problem in my case was a vac line was sitting a bit loose under the hood and was rubbing against a piece under the hood. It ended up rubbing a hole right through the line to the cruise control but at the same time, would actually close the hole enough at times for the cruise to all of a sudden work for a short bit. Fixed the line and the problem was gone.