Intermittent cruise control not engaging engine sounded rough when it worked this time

Hi,

It sounds like the electrical portion is working. However, there is a servo that operates from engine vacuum. Based on your description, it sounds like there is a vacuum leak not allowing the system to work and causing a rough idle.

I attached pics below of the two places to check. There will be engine vacuum hoses going to and from them. Check to make sure nothing is disconnected, cracked, or leaking. Also, there is a vacuum reservoir that is part of the battery tray. Make sure to check for cracks and leaks there. The 3rd pic shows vacuum hose orientation at the throttle body.

If you start the engine and open the hood, you may hear a hissing sound which would indicate a leak, so try that. Also, here is a link that explains how to check for a vacuum leak:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know what you find or if you have other questions.

Take care,
Joe