Skip the auto shop - Our mechanics make house calls

Q: Idle fluctuates and then stalls.

asked by on

Hello!

My car's battery was dying toward the end of last year, so I had the battery replaced at a mechanic's shop. Then, less than a month later, the battery completely died again. I bought a new battery, set up an appointment through YourMechanic, and someone came out to replace my alternator and battery and do a visual inspection of everything else, and my car ran normally for about a month of very infrequent driving until this weekend. Now, all of the sudden, the car has an extremely low, rough idle when stopped, and there's a loud screeching noise coming from the engine area that's loudest when idling and a bit quieter when gas is applied. The visual inspection said that most of my car (including engine, belts, etc) was "excellent" so I'm not sure what the problem could be. Any help would be appreciated!

My car has 66000 miles.
My car has an automatic transmission.

Hi There, It sounds like you may have a belt that needs to be tightened as this will cause a screeching noise when a belt is loose and the engine is running at any pace. This can be fixed usually by tightening the tensioner pulley. The low idle may be caused by a dirty or faulty idle air control valve. The idle air control valve is a small valve on the engine’s intake system that reads the air intake as it comes into the motor. This is controlled by the car’s ECM which uses this information to make adjustments to the air/fuel ratio depending on various inputs such as outside air temperature, intake air temperature, load and various other things. As you accelerate, your car’s engine is receiving a much higher dose of fuel than when at idle and conversely, when you let off the gas pedal, there is a sudden change in this fuel supply as a result of your foot letting off the pedal. When this happens, the job of the idle air control valve is to bring this deceleration down to a slow and smooth idle rather than suddenly cutting off the fuel supply causing the motor to die. When the idle air control valve is not working properly, this cause a disruption in this process resulting in the engine not being able to idle properly. I would recommend having a professional come to your location to diagnose and inspect your vehicle.

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

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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: Dropped a 10 mm wrench inside the engine compartment.

You may not have any worries unless the wrench gets in a place where it makes noise or interferes with vehicle components. The wrench may have fell into the inner fender. You may be able to locate it there. Have...

Q: My Porsche Cayenne is shutting down in traffic and cutting off when I start the vehicle

When your car stalled, most likely it set one or more trouble codes in the engine ECU. Those codes can be read by a technician equipped with a Porsche appropriate scan tool. You might be able to see the problem...

Q: Power steering went out. Turn signals and speedometer won't work. As well as heating

Hello there, many faults will cause your power steering to go out and the P0500 and P0705 codes to be found on your 2010 Scion. Without knowing the model of your vehicle I can only offer general advice. If both...

Related articles

Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
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...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.