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Will not start

Discussion in '1st Gen. Tacomas (1995-2004)' started by 97 Tacoma, Jan 28, 2012.

  1. Jan 28, 2012 at 5:47 PM
    #1
    97 Tacoma

    97 Tacoma [OP] Member

    Joined:
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    Minnesota
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    97 Tacoma 4WD 2.7
    First time user; please bear with me.

    I replaced the original rusted through exhaust (cat back) with a standard system. Unbolt the ehaust then unhook the O2 sensor and repeat in reverse. All is well except the MPG went from 16-17 (city) to 12. Thought it might be the rear O2 sensor since I removed and reinstalled the same one; maybe I damaged it(?). Figure I would cover the obvious: replaced air filter, plugs and wires, no change.

    Good battery voltage at both sensors when checked with ignition on "run" but engine off. Resistance of rear O2 sensor was good at 13 (should be 11-16 ohms). Front O2 sensor read the same 13 ohms but Haynes and Service Manual says it should be 5-7 ohms. Seems likely the front is bad.

    Trying to all I can myself as times are tight I follow Haynes' recommendations and back-probe the terminals, start the engine and begin to measure the voltage (should start and .1v and get to .9v after engine is warm).

    Somewhere in the process of laying under a running truck on a frozen Minnesota concrete floor the two back-probes must have touched (that is a guess). The truck dies, I try and start it: no go. Remove the back-probes; still won't start. Unhook the battery for a while (head in to thaw the fingers) then try to start it again: nothing. Unhook the front O2 sensor (thinking it's fried) and it still won't start. It should run without the sensor connected.

    My fear is that I cooked the computer or something else serious. Ideas of what to do next are appreciated.

    Thanks
     
  2. Jan 29, 2012 at 2:02 PM
    #2
    97 Tacoma

    97 Tacoma [OP] Member

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    Took a break and realized I should check fuzes to see if any were blown. EFI fuse blew (why the engine stopped). Replaced and truck will run again.

    Also noticed that a hose was lying loose. No idea when it happened. It goes from the air cleaner housing to the charcoal canister and looks like it connects to the vacuum switching valve (the front connection).

    Filled the tank and will see what MPG is. Probably will order new O2 sensors (from Rock Auto; $57 vs. $107-$119 locally) and install; they are original with 85,000 miles (no, that is not a typo; 97 with 85k).
     
  3. Jan 29, 2012 at 2:25 PM
    #3
    maineah

    maineah Well-Known Member

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    If you are reading battery voltage you are checking the heater voltage not the O2 sensor it's self. It needs to be running and hot the voltage should range be between .1 and 1 volt and be active (changing) Yes it will run with out the sensors hooked up. I believe your sensor has 3 wires 2 white and 1 green the green on is the sensor output.
     
  4. Feb 10, 2012 at 11:41 AM
    #4
    97 Tacoma

    97 Tacoma [OP] Member

    Joined:
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    Male
    Minnesota
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    97 Tacoma 4WD 2.7
    Thanks for the post.

    Yes I ws checking battery voltage first. I will re-attempt with the O2 sensors unhooked. WAY easier. Haynes says to back-probe those wires to measure voltage change between .1 and 1 volt. Not the easiest task.

    Also noticed that the lower radiator hose is cold at all times; warm engine with heater on or off does not matter. Going to also replace thermostat and fluid.
     
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