Edmunds Answers



  • zaken1 02/29/12 4:07 pm PST

    That is a good description of what commonly is called "lean surge." It is caused by a combination of the extremely lean air/fuel mixtures used in late model low emission engines; and the resultant increased sensitivity of those engines to ignition components or fuel metering systems which need servicing. Here's what I would do to address this situation:

    1> Inspect the air filter to see if sunlight or a bright light passes easily through the element. Replace the air filter if light does not easily pass through it.

    2> Replace the spark plugs with a set of Bosch Iridium #9612. This particular plug has a unique design; which is more effective in igniting lean fuel mixtures than other plugs. If your local parts store does not have these plugs; they can order them from a warehouse. Or, you can buy them online from www.rockauto.com The gap on these plugs should not be adjusted.

    3> Have the mass airflow sensor and the throttle body thoroughly cleaned; being sure to only use mass airflow sensor spray on that part, and not touching the sensor wires with hands or any tools. Be sure to clean the back side of the throttle butterfly, and pay particular attention to the throttle body bore where the edges of the butterfly touch it.

    4> Buy a bottle of Chevron Techron combustion chamber and fuel system cleaner and add the full bottle to the fuel tank just before filling the tank with fuel. This is another unique product; which removes the deposits that built up on intake valve stems and cause lean surging. Other cleaners do not work as well for this. Techron can be bought at Chevron gas stations, Wal-Mart, Auto Zone, and O'Reilly parts stores. It usually takes 50 to 75 miles of driving for this miracle product to do its work.

    5> The fuel sold in many states has large amounts of ethanol added to it. Ethanol will cause lean surging. Switching to a different brand of fuel will often improve this problem. There is a website which lists gas stations that do not have ethanol in their fuel: www.pure-gas.org
    If you don't use ethanol free gas; Shell is one of the fuel brands which will probably run best.


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