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I don't use my cruise very often but I was on a long drive the other day and set my cruise. The car would not hold a steady speed. It kept slowing down then speeding up over and over. I set the cruise today and it's doing the same thing. Does this symptom point to any particular component failure on the cruise system?
 

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Gee wish someone would reply,having the same problem.Searched the archives and didn't find any pertinent information.

Later
Rich
 

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I'm not all too familiar with the 5.0 engine so bear with me. First, is the cruise control controlled by a vacuum diaphragm or an electronic solenoid? If the latter, I can't help you. If the former, check to make sure there are no leaks in the vacuum lines, especially those to and from the cruise control diaphragm. In addition, be sure that the diaphragm itself is in good shape (fastened tightly, and no cracks). By the way, a cruise control diaphragm looks like the second photo down on this website:

http://auto.howstuffworks.com/cruise-control2.htm

Be absolutely sure you've diagnosed all vacuum-related possibilities before moving on to the rest of the system.

Other problems can include loose connections like the cables that attach the system to the throttle, and perhaps even a malfunctioning throttle position sensor (?). Hope this helps guys...

-DG-
 

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I had the same exact problem with my '95/4.6. It would set, then loose speed, when it got to a point, it would accelerate to get back where it was set, go past it a bit, then loose the speed again (over and over). It was the cruise control servo located in front of the drivers side wheel. After I replaced it ($125, IIRC), it has worked fine since.
 

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to get to it, you have to remove the plastic inside the fender... it's about 4" in front of the fender...
 
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