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    #1

    4-wire O2 on a box

    Hi

    I'm thinking my O2 sensor is bad and I was thinking with the short distance I usually drive I would greatly benefit from a heated O2 sensor. I've ran a wire from my current sensor inside the car and I'm going to hook my dmm up to it later today so I can monitor the output voltage to make sure it is not sending proper signals.

    Has anyone done this conversion? If so any tips? It should be a pretty easy swap.

    My thought is to connect the heater either to a switch on the dash, a timer that automatically comes on when the car is started, or a combination of the switch and the timer to make sure I don't forget to turn the switch back off. I suppose there is a fourth option if you assume that it will be up to temperature at the same time the engine gets up to temperature and wire it up to be on when the engine is running and not up to temperature.

    For now I'm thinking of just using a simple switch and later using more complicated logic when I make my digital dash which would already have a temp sensor running to a microprocessor so it would not be much to have it signal the heater.

    If my current sensor is bad I'm planning on doing the swap next weekend so check back next week if you are curious how this turns out.
    '85 Mercury Grand Marquis
    only MSD multi-spark so far but hopefully a 351 on the way.
    Tags: None
    #2
    The SEFI boxes use them. They have power whenever the ignition is switched on. Just tie in a power wire from a switched source (run) and a ground wire, ground it to the engine. There's your HEGO. O2 Wiring Layout can be found here http://fordfuelinjection.com/?p=31 Be careful to route the wiring away from the exhaust manifold or you have the chance of melting the wires. When the engine is cold, it doesn't use the data from the O2 sensors. This is known as Open Loop mode. When it warms up, it then looks to see what the O2 Sensors are reading. I believe that the CFI boxes ran 1 O2 sensor, but I can't remember.

    Comment

      #3
      Originally posted by 86VickyLX View Post
      The SEFI boxes use them. They have power whenever the ignition is switched on. Just tie in a power wire from a switched source (run) and a ground wire, ground it to the engine. There's your HEGO. O2 Wiring Layout can be found here http://fordfuelinjection.com/?p=31 Be careful to route the wiring away from the exhaust manifold or you have the chance of melting the wires. When the engine is cold, it doesn't use the data from the O2 sensors. This is known as Open Loop mode. When it warms up, it then looks to see what the O2 Sensors are reading. I believe that the CFI boxes ran 1 O2 sensor, but I can't remember.
      Thanks my quick research made it sound like the heater was usually controlled by the computer so I assumed it only kept it on long enough to get up to operating temp and then shut off the heater. That makes it much simpler if it can just be on when ever the car is on.

      I figure that once I get the block heater installed the engine will be up to temp quicker than the sensor and since my drive to work is only 6mi the quicker I can get my car up to operating temp the more gas I will save. Also the heated ones last a lot longer since they burn off the carbon build up themselves. So if I need a new one I figure I might as well take advantage of the new technology.
      '85 Mercury Grand Marquis
      only MSD multi-spark so far but hopefully a 351 on the way.

      Comment

        #4
        sefi cars have a 3 wire sensor. Not sure what the difference is, but I believe the 4 wire has a ground, and the 3 wire grounds to the exhaust? If thats the case, you're good. Ground the ground, run the sensor wire to the original CFI wire, and power the heater.
        86 Lincoln Town Car (Galactica).
        5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

        91 Lincoln Mark VII LSC grandpa spec white and cranberry

        1984 Lincoln Continental TurboDiesel - rolls coal

        Originally posted by phayzer5
        I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

        Comment

          #5
          From what I've read the difference from the 3-wire to the 4-wire is that in the 3-wire the heater and sensor share their ground and in the 4-wire the sensor has its own ground so it can be shielded and prevent interference from the shared ground.

          I'm not sure my O2 is bad now. I monitored its output this morning while running some errands and most the time it outputs a valid reading around .7 to .9 volts and when it is outputting those readings the engine is not taking any action to get a better mix. Some times I was getting bogus readings but I'm wondering if that is because it is getting to rich for the sensor to output a valid reading. Since it takes no action to correct the rich mixture it seems like it is always running in open loop so I'm thinking about replacing my temp sensor first. Oh and the car is running around 190 degrees when I'm watching the O2 output.
          '85 Mercury Grand Marquis
          only MSD multi-spark so far but hopefully a 351 on the way.

          Comment

            #6
            last wierd fueling problem I had with a CFI car did turn out to be the O2 sensor. I tried testing it with the propane torch like I read about somewhere, and it didn't respond correctly. I may have done the test wrong though, I don't know. Either way, it quit running pig rich and sucking fuel with the new sensor.
            86 Lincoln Town Car (Galactica).
            5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

            91 Lincoln Mark VII LSC grandpa spec white and cranberry

            1984 Lincoln Continental TurboDiesel - rolls coal

            Originally posted by phayzer5
            I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

            Comment

              #7
              Well I swapped out the temp sensor this morning before heading to work and when I was getting readings from the O2 they were better(not so rich) but it is still giving me messed up readings and it is not just climbing and then giving weird reading so I think the O2 is bad too. Probably just going to do the 1-wire though due to money and the fact that I still have not figured out whats wrong with my wife's van and I just noticed while working on the car this morning that some of the fins on my radiator are wet so I must have a small leak in the radiator so I'm going to have to replace that soon too.
              '85 Mercury Grand Marquis
              only MSD multi-spark so far but hopefully a 351 on the way.

              Comment

                #8
                new 1 wire is like 20 bucks if you get the generic. Have to splice the plug, but thats minor.
                86 Lincoln Town Car (Galactica).
                5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

                91 Lincoln Mark VII LSC grandpa spec white and cranberry

                1984 Lincoln Continental TurboDiesel - rolls coal

                Originally posted by phayzer5
                I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

                Comment

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