While driving incline up to 4000 feet the rpms fluctuate between 2500-3000, speed stays at 55mpg. Engine sounds loud buzzing. AC is turned off to prevent overheating for 10 miles during the incline at this time. No codes. Mechanics cleaned the throttle body, fuel injectors and i got a new thermostat. Still having problems. All fluids are on schedule. Mechanics cant figure out whats wrong because theres no code. They want to charge me again to look at the same problem. 2011 Mitsubishi Ourlander ES, odometer 139,341.
Try replacing your MAP sensor. About $55. Also, as you go up in altitude, there is less atmospheric pressure and less oxygen content in the air. The computer should be reading this through the 02 sensors and enrichening the air/fuel mixture as you gain altitude.
Make that leaning out the mixture, not enrichening it.