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Q: Car wont stay running

asked by on

why a car will start and idle a little bit,then quits.will start right back up,run a few then quit

My car has 92498 miles.
My car has an automatic transmission.

Hi There, It sounds like you may have a dirty or faulty idle air control valve or potentially a bad fuel pressure regulator or fuel pump. The idle air control valve monitors the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. This valve is controlled by the vehicle’s computer and will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed with the help of the idle air control valve making the transition from a higher RPM back down to idle speed while adjusting the air/fuel ratio constantly to allow this to happen smoothly.

As you know, when you turn the key to on, the fuel pump is activated and the fuel system is primed with fuel at a specific pressure in order to supply the fuel injectors with enough fuel to start the motor. When this is less than what is needed in order for the motor to fire or in some cases higher than normal, you may notice an erratic fluctuation in engine RPMs or hard starting. I would recommend having an expert from YourMechanic come to your location to diagnose your fuel system.

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