Car Stalls at Idle

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Car Stalls at Idle

Generally speaking, car stalls at idle is an indication of a fuel problem specifically lack of fuel. Reasons which cause the car to stalls at idle are a bad idle air bypass valve, a bad cold start valve, or a bad fuel pressure regulator.

Reasons why car stalls at idle
1. Bad idle air bypass valve
2. Bad cold start valve
3. Bad fuel pressure regulator

What to do?
Quickly step on the gas pedal and observe if the engine will continue running. If the engine continues to run it means that the problem is a bad idle air bypass valve. Fuel injection car has a device called idle air bypass valve, the purpose of this device is to maintain the idle speed of the engine. If this device is not functioning properly then the engine will stall. When the gas pedal is depressed when the engine is about to stall is an indication of a bad idle air bypass valve. By stepping the gas pedal will increase the throttle which compensates for the bad idle air bypass valve giving the engine enough fuel to continue running.  Replace the bad idle air bypass valve to correct the problem.

However, if the engine will not continue running even when the gas pedal is depressed then it’s not a case of a bad idle air bypass valve.

Now, observe if the car stalls while driving happens only if the engine is cold but will not happen after the engine has warmed up then the problem is a bad cold start valve. Fuel injection car has a device called a cold start valve. The purpose of this device is to keep the engine running when the engine is cold by providing the engine more gas so that the engines have a rich air/fuel mixture. Replacing the bad cold start valve will fix the problem.

If the air bypass valve and the start valve is not the problem then the only remaining possible reason why your car stalls while idling is a bad fuel pressure regulator. Generally speaking, car stalls at idle is an indication of a fuel problem specifically lack of fuel. Fuel injection car has a fuel pressure regulator, the purpose of this device is to maintain the fuel pressure to each of every injector. If there is a problem with this device the engine will be deprived of fuel which will cause the car to stall. Replace the fuel pressure regulator to fix the problem.


Bring the car to a shop and ask the mechanic to verify the problem, if the problem is confirmed replace the defective parts as necessary.


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