Sudden RPM increase
 

I own a Terracan 07 2.9 crdí diesel. Just this week all the sudden the car idles at 1000 rpm . It used to idle at around 800 rpm perfectly. When I put the car in Drive it takes off. When I brake it goes down to about 800 and as soon as I let go the brakes it goes up.to 1k rpm. Any Idea.if it has to do with a sensor o what the cause may be? Thanks. I'm in Central America in Panama.