Skip the auto shop - Our mechanics make house calls

Q: when in park or stopped at a red light my car seems like its about to shut off

asked by on

when i'm in park or stopped at a red light my car all of a sudden drops RPMs to about 500 about to shut off and then goes back to 1000-1500 RPM.it also starts to shake but then when i start to drive it seems to be fine

My car has 101000 miles.
My car has an automatic transmission.

A: Low or surging idle speed can be caused by ...

Low or surging idle speed can be caused by a number of different things. A vacuum leak can cause this. If a vacuum line is broken or detached, or the intake manifold gasket is cracked, the engine will draw in too much air, effecting the air/fuel mixture and ultimately the idle speed and performance. Also, a faulty idle speed or idle air control motor can be at fault. Sometimes the idle air control motor can be "lazy" - does not respond as quickly as it should - and not set a fault that would cause the check engine light to come on. That can happen due to age/mileage, or the throttle body can have carbon build-up that slows it’s reaction time. The mass air flow sensor can also be at fault. If it does not measure incoming air correctly, it can cause stalling, poor idle, lack of power and poor fuel economy.

Have a certified technician look into the poor idle to isolate the exact cause.

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: Loss of power - 2006 Infiniti G35

Hi and thanks for contacting YourMechanic. Since you are getting different sensors acting up, check all of the connections to all of the sensors and make sure that there is no missing bolts. There could be a vacuum leak causing...

Q: Smells like burning oil

It sounds like you have been doing your best to keep your car running top notch! Sometimes even with our best efforts, problems can arise from certain cars, which are often of no fault of the owner. From the description...

Q: The new ignition is locked, cannot turn over

Hello. When you install a new ignition and a new computer, it needs to be reprogrammed to communicate correctly. This can usually only be done at the dealer. If they are not programmed correctly then the computers will not communicate...

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...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
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...