Cruise control will not hold speed

[Copper93]

I have a 2013 Expedition Limited. My wife told me the cruise control doesn't hold its speed very well. When set to 70 mph, it will drop to around 63/65 when going up hill. It holds on flat ground. I haven't checked anything out but will this weekend. Any suggestions on where to start?

 

[1997SCEBFEX]

gradual incline, or a significant grade? it didn't downshift to maintain speed? if a slight & extended long grade, it might not shift.
as you know, these are heavy vehicles.

as far as anything wrong, not sure where to start. vacuum leak?

sure others will chime in.

 

[stamp11127]

The ecm may be programmed to allow a slight decrease in speed when going uphill. Try a steeper hill and see what it does.