While on cruise control going down the freeways (at any speed settings) the engine will drop rpms for about a half second. Noticable while driving but don't see any rpm drop on the tach. This will happen at random but on every long drive. When I cancel the cruise control and drive without it, there are no rpm drops. I thought the throttle body valves would be sticking and cleaned them but the problem remains. Any ideas?

 

TPS (Throttle position sensor) 35-40 bux and 15 minutes of work. Good luck.