Friday, February 12, 2010

True or False: When the engine is cold the computer function will be in ';open loop';?

Please explain.True or False: When the engine is cold the computer function will be in ';open loop';?
That's somewhat true for the fuel trims, ie the length of the fuel injector pulses. There is air control and timing control being done, of course, but until there is a stable (in spec) reading from the O2 sensors, the machine is running without that feedback (thus, open loop).





Newer cars have heated sensors (HEGO in your Haynes manual) that speed up when you hit the temperature at which the exhaust gas can start to interact with the material of the O2 sensor (heavy metal oxide, non-stoichiometric, so O2 in hot gas stream changes the balance of oxygen vacancies and a current is established to keep the material neutrally charged).

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