"A/C problem in acura 2.5 Tl 1996"

1996 Grey Acura 2.5 TI Front View

I have an Acura 2.5 TI 1996. My car is having weird problem that i dont understand and professional even. When i turn my a/c on it works real good but when i stop at traffic light my speedometer gauge (which say number 1,2,3,4) goes up and down constant until i turn my a/c off. I went to mechanic and he said about air pressure was not enough and he did chared me $125 about that. But after a day it did the same thing. It was not an air pressure problem, i think there is something going on with my colling fan or cut off system. Please let me know if someone knows about that?

Answers : That is called a tachometer, not a speedometer. It tells the engine rpm. If your idle goes up and down when the ac is on, it’s a problem with a sensor or something in your fuel management system. Probably a IAC, which is an Idle Air Control Valve. This is what keeps your car idling at a particular speed. It could also be any # of sensors, like your Throttle Positioning Sensor, Mass Air Flow sensor or Manifold Absolute Pressure sensor. Or it may be as simple as a dirty air or fuel filter. Have a mechanic solve this, and not the same mechanic as before.