Skip the auto shop - Our mechanics make house calls

Q: Why a vibration is felt when the AC is on during stops on street lights?

asked by on

When the AC is on and I make a stop on a street light, I feel a vibration that seems to come from the engine. The vibration in that situation is not steady. It comes like the waves in the ocean. it can stop for a little while and do it again. When I driving the car I don't feel the vibration. I appreciate your help.

My car has 25000 miles.
My car has an automatic transmission.

A: Hello, thanks for writing in. This vibratio...

Hello, thanks for writing in. This vibration is usually the result of low idle. When loads such as the AC system or a steering wheel turn are placed on the engine, the idle needs to rise to offset this. If it does not, then the engine will begin to run rough. Most of the time this is caused by a dirty throttle body. When the throttle becomes dirty the computer has a hard time trying to maintain an idle. It can also be caused by a worn engine mount so I check those also to try and isolate the problem. I would recommend having an expert from YourMechanic come to your home or office to confirm a diagnosis on the rough idling issue, and make or suggest the necessary repairs or replacements.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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: Clicking sound when starting

The rapid clicking is generally an indication of a battery that is either drained or going bad. The battery will need to be charged and load tested to determine whether or not it is good. If the battery tests good...

Q: front passenger wheel well smoking

The unusual high heat on the right front side could be due to a failed wheel bearing and/or a stuck brake caliper. If you compare the brake rotor temperature, left versus right, using an infrared thermometer you can determine if...

Q: Is it my pulley on the power steering pump I need to replace if it's wobbles or the pump it's self

Remove the power steering belt and turn the pump by hand to monitor the shaft to see if it moves around as you turn the pump. If the shaft is not moving and stays straight when you turn the pump...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
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.