Q: Car runs rough with AC on

asked by on

My car drive perfect without the ac on.as soon as I turn on my ac I feel a vibration on my steering wheel

My car has 119000 miles.
My car has an automatic transmission.

It sounds like you may have a bad AC compressor or potentially a faulty MAP Sensor. When the AC compressor is beginning to fail, this may incur an increased load on the motor as it works harder than usual to turn a bad compressor. This increased load causes the motor to work harder than it otherwise normally would, resulting in the motor overheating.

The Manifold Absolute Pressure (MAP) sensor senses engine load and generates a signal that is proportional to the amount of vacuum in the intake manifold. The engine computer then uses this information to adjust ignition timing and fuel enrichment. When the engine is working hard, intake vacuum drops as the throttle opens wide. The engine takes in more air, which requires more fuel to keep the air/fuel ratio in balance. When the computer reads a heavy load signal from the MAP sensor, it adjusts the fuel mixture to slightly more rich than normal so the engine can produce more power. The computer will then retard (back off) ignition timing slightly to prevent detonation that can damage the engine and decrease performance. This may also be caused by other closely related components such as a dirty or failing mass air-flow sensor, a faulty throttle position sensor or potentially a vacuum leak. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Car runs rough with AC on

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Lug nuts coming loose

I would certainly be concerned about the lug nuts falling off originally. However, I would not worry about the cap that had fallen off recently if the nut is still tight. Many times manufacturers will apply these chrome caps to...

Q: Battery drained, solenoid doesn't engage - 2008 Mercedes-Benz B200

Hello. The battery is located under the front passenger seat. The seat lifts up and pulls forward to allow access to the battery. However, if your battery is 8 years old, it would be best to replace the battery with...

Q: Car makes clicking sound, but doesn't start.

It is very possible that the battery may be compromised. When a battery is drained completely it becomes very difficult for it to charge back up again. Severe damage may have occurred within the battery while it was draining. I...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...