Q: Car RPM drops on AC, stalling the car.

asked by on

My Nissan Sunny's RPM drops dramatically on AC. We had the compressor and the wirings checked but the issue remains. My mechanic told me we need to change an "auto choke sensor" , which according to him regulates RPM. Another mechanic told me to change the whole throttle body.

I just want an expert opinion on what an auto choke sensor is, and will it indeed help regulate RPM, before I go ahead and spend money on the problem. Im a student and so I want to make sure Im spending my money on the right thing.

PS. The RPM also drops when braking or turning the steering wheel, but the car only stalls on AC when I lift my foot off the accelerator.
My car has a manual transmission.

Hi There, This may be a sign of a faulty MAP sensor as the vehicle responds adversely to a load put on the motor (i.e. putting it in gear, turning on AC or engaging the brakes). 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 RPM drops on AC, stalling the car.

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: car starts sometimes and sometimes doesn't

Intermittent no starts can be the hardest problems to diagnose and the transmission issues would not cause the no start. You may have a sensor or fuel pump issue and should have systems tested by a mechanic like one from...

Q: My vehicle has problems when accelerating and it makes like some kind explosions.

You should have the fuel pressure checked first and then scan the computer for any codes and have them repaired as needed. The lack of power may be a low fuel pressure or clogged fuel filter problem. If these are...

Q: Accessory / Ignition Power is inconsistent

Hello there, thank you for asking about your 2004 Nissan 350Z. This is a commonly known issue with the 350Z. You should have a Check Engine Light on when this happens which will be likely related to NATS computer codes....

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...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.