5 Symptoms of a Bad Purge Valve

By | August 3, 2023

Symptoms of a Bad Purge Valve
A bad purge valve can have varying symptoms and will need to be examined and tested to see if it has failed.

The main symptoms include the engine light staying on, less fuel mileage, and failing an emission test.

What is the Purge Valve?

What is the Purge Valve
The purge valve is a component in a vehicle’s EVAP system which is for emissions.

The EVAP system sends gas vapors from the gas tank to the engine to be burnt away.

This reduces emissions since the gas vapors do not escape into the atmosphere.

A purge valve will open when the engine is running to let the gas vapors into the engine to be burnt away.

When the engine is off, the purge valve closes, so no gas vapors escape.

5 Symptoms of a Bad Purge Valve

  • Check Engine Light Stays On
  • Check Engine Light Stays On
    A bad purge valve will cause an engine code which the onboard computer will indicate by turning on the engine light.

    An OBDII scan tool can be connected, and the codes read that are stored on the onboard computer (ECM).

    Common purge valve error codes include P0441, P0442, P0443, and more.

  • Vehicle Fails Emissions Test
  • Vehicle Fails Emissions Test
    The purge valve is a necessary component in the EVAP system which is for emissions.

    If the vehicle fails an emission test, the purge valve may be the cause.

    There are several components that can fail in the EVAP, with the purge valve a common issue.

    OBDII error codes can be read from the vehicle’s onboard computer to see if it has failed.

  • Engine Idling Badly
  • Engine Idling Badly
    When a purge valve fails, it sometimes can cause a vacuum leak which can cause the engine to idle badly.

    They can also fail and not cause a vacuum leak, and the engine may run normally.

    Which part of the valve has failed can cause different symptoms.

    For example, if the valve is stuck open, it may cause a vacuum leak, and the engine may idle badly.

    If the valve is stuck closed, there may be no vacuum leak, and the engine will idle normally but would fail an emission test.

  • Long Start After Fueling Up

  • A purge valve that is stuck open can leak gas vapors into the manifold while fueling up, which can cause long start times.

    The vapors will need to be flushed out of the manifold before the engine starts, which can take several rotations of the engine

    While not too common, it can be an issue for some vehicles if the valve is stuck in an open position.

  • Fuel Mileage is Worse than Usual
  • Fuel Mileage is Worse than Usual
    The Evap system recycles gas vapor into the engine to be burnt away.

    While mainly for emissions to help contain the gas vapors, this can also add to fuel mileage.

    It will not have a huge impact on gas mileage, but depending on the vehicle, it can cause it to get less gas mileage than usual.

Common OBDII Codes for a Failed Purge Valve

  • P0441 Evaporative Emission (EVAP) Control System Incorrect Purge Flow
  • P0442 Evaporative Emission (EVAP) System Small Leak Detected
  • P0443 Evaporative Emission (EVAP) Canister Purge Valve Circuit Malfunction
  • P0451 Fuel Tank Pressure (FTP) Sensor Range/Performance Problem
  • P0452 Fuel Tank Pressure (FTP) Sensor Circuit Low Voltage
  • P0453 Fuel Tank Pressure (FTP) Sensor Circuit High Voltage
  • P0456 Evaporative Emission (EVAP) System Very Small Leak Detected
  • P0457 Evaporative Emission (EVAP) System Leak Detected Fuel Fill Cap Loose/Off

How to Test a Purge Valve?

There are several methods to test a purge valve, including using a vacuum pump or a multi-meter.

A common method to see if it has failed is to remove the hose going to the charcoal canister.

After the hose is removed, start the engine and check for a vacuum at the valve.

If there is a vacuum while the engine is cold, the valve has failed.

After the engine warms up, the valve should open, and a vacuum should be present at the valve.

If there is no vacuum at the valve after the engine warms up, it has failed.

Can A Vehicle Drive with a Bad Purge Valve?

Yes, most vehicles will continue to run and can be driven with a bad purge valve.

Often there, other than an engine light on, there are no other symptoms

It can vary between vehicles and which part of the valve has failed, but most can continue to be driven.

Summary
A bad purge valve can sometimes cause engine performance problems and can have various symptoms.

Common symptoms will include the engine light staying on and failing an emission test.

The onboard computer will store error codes that can be read with an OBDII scan tool.

The error codes will point o an issue with the purge valve,

The valve can also be tested using several methods to see if t has gone bad.

Have you had an issue with a bad purge valve? What symptoms did it cause? Let us know below.

Bob Thomas

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