erratic cruise control

[1989fiveohman]

hey guys ive got a 96 cobra and was wandering what you might think would cause problems with the cruise control,its worked fine up until we were coming home from mustang week last sunday and about halfway home after coming down a hill the cruise was only slowly accelerating back up not like it should have been until the point it just stopped accelerating and the cruise wouldnt resume or nothing and you can turn off the cruise and right back on and it will work so so for a few minutes and the it starts the slow accelerating again and finally shuts itself off again, and when you first turn itt on it now it kinda makes the car surge back and forth slightly for a mile or two before ever leveling out but soon after quits working any ideas on where to start looking? thanks for any advise

 

[wmburns]

Suggest starting by looking for vacuum leaks (just to be sure).

Does the speedometer work correctly?

Check the throttle body and cable for binding. Check to see if both throttle return springs are attached and in good shape.

Check the electrical connection to the cruise control itself. Ensure there are no bent/pushed pins and that the connector itself is clean and tight. Double check that the throttle cable moves easily through the jacket (most likely the most important test).

I will double check with my 96 wiring diagrams but I am reasonably sure that the car's speed comes from the PCM (don't have the 96's diagrams at the office).

Unless something else is found, perhaps the cruise control module itself has gone bad.

 

[1989fiveohman]

thanks wmburns do these models have vacum operated cruise control? there shouldnt be any bent connections, nothing has been taken apart on the car related to the cruise control (i only know this cause we bought the car new) it works fine when you first turn it on now for about 10 or 12 miles but then it starts slowly slowing down till the CC just cuts itself off i will take a look and see if there are any vacum line going over the way the cable comes from... oh and the speedo works fine and i will check for any binding and make sure the electical connections are clean and tight

 

[Price1]

Another vehicle we owned, the cruise control would work for about two minutes then shut down. As it was brand new, the control module was the culprit and was replaced.

Good luck.