1999 Durango, 5.2L, 4WD, Automatic and 135K miles.

Cruise control turns on without a problem and will set and hold speed on level roads but allows the vehicle to loose speed on the uphill. Additional issue is when setting the cruising speed the vehicle slows down about 5mph before engaging and then slowly climbs back to the set speed. Any suggestions on what the cause can be and how to fix it?

 

If it's vacuum controlled, look for a vacuum leak somewhere. My Journey did that when we first bought it, the dealer had to reflash some computer module to get it right. Not sure if that could be done to yours.

 

It is vacuum controlled, so that is a possibility.

 

none of the above. Try replacing the TPS sensor usually located on the throttle body.

This happened to me and after spending a month with the dealer trying to resolve this, a user in this forum recommended replacing the TPS sensor.

Replaced my TPS sensor and the erratic cruise control issues are all resolved.

 

Thanks all for the replies I found the problem this morning and it was a vacuum leak. Small hard plastic vacuum line rubbed against the filler tube for the automatic transmission and wore a hole in the line. For the moment I wrapped electrical tape around it and will do a permanent fix later. I have to buy the right diameter vacuum line so I can cut out the bad section and replace it with the new hose.
Warren

 

Glad it was a simple fix.