ef civic - oxygen sensor retrofit

Discussion in 'Civic' started by jim beam, Feb 14, 2011.

  1. jim beam

    jim beam Guest

    thought y'all might be interested to know that you can retrofit a 4-wire
    sensor onto an older 1-wire civic without upgrading to the obd1 ecu.

    did this recently on my 89, and have been delighted to find my urban
    fuel economy has improved significantly - it's jumped from 29-30mpg
    crawling around san francisco, up to ~35mpg. no noticeable difference
    on freeway driving, but the overall average for mixed use improves.

    i have the heater wired into the yellow/black wire that is the same
    circuit at the fuel pump supply and the fuel injectors, the sensor
    ground and heater ground common-connected to the engine block, and the
    sensor output wired onto the old sensor input on the existing harness.


    note: this is not california legal for smog. even though it improves
    emissions because the ecu goes into closed loop much quicker and stays
    closed during prolonged idle, smog checks require the original 1-wire
    sensor to be present and wired as per factory. so, keep your old
    sensor, use it for smog inspection, then switch back to this 4-wire
    solution for daily driving. i used an old 4-wire socket from a junkyard
    civic and bullet connectors to make this easy, and so there is no
    permanent modification to the stock civic harness.
    jim beam, Feb 14, 2011
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