A/F Gauge problems (electric novice)

  • #1

    A/F Gauge problems (electric novice)

    Hey everyone I hope this is the right area to put this but anyways here we go. About a couple of weeks back I bought a new A/F gauge from Autometer, one of their Z series if that might help, and followed the instructions to install it.

    I ran the power wire to the radio power and replaced the 15amp fuse with a 20amp in compliance to the part where it said I needed to install a 5amp in-line fuse. Then I ran the ground wire to a body ground, and the signal wire to the yellow wire on the body side of the 02 sensor harness. I soldered all my connections and the only thing that I did different is the signal wire was too short so I had to use an extension (I used 14 gauge wire instead of the 16 gauge wire, don't know if that makes a difference) Yet the only display I get is the farthest LED for rich, but after a while I can see the next green down and a couple of the yellows trying to show but you can only see this at night.

    Well after going over my wires again and testing all my connections I notice that more of the LED's will display if the connector is moved around and it is loose, but once tightened back down it goes back to displaying full rich. So I ran the ground to the negative battery cable, and still no difference in the display. So then I did a basic tune up, K&N filter cleaned, sparkplugs changed (showed normal wear), and checked my timing (in time). The only reasons why I haven't replaced the O2 sensor is because the guy I got the motor from said the the sensor was replaced not more than 5-10,000 miles ago, and the fact that it is still sending a good signal, yet I might replace it just to see if that could fix it.

    I talked with a couple of guys in the local Z car club here in Nebraska and one of them suggested the being as I had to extend the signal wire length it's affecting the signal that the gauge is reading. Because the gauge is calibrated to only read a signal over that distance of a wire. I'm not sure about this cause I thought it'd stay the same, then again I'm not a electrical wizard and I'm sure someone here is.

    Any advice would be helpful, and thanks in advance.
    Bah-chicka-wow-wow
  • #2
    mmm i dont get the part were you installed a 20amp fuse when it should be a 5 amp..... try to eliminate the added signal cable to make it one piece, also conect power to the batery not into the radio and check all conections again.... hope it helps, i havent installed one of those yes but rechecking your conections will fix 95% of problems,,, also check your ground wire (if it has one)

    As i walk thru the valley of rice, i fear no Honda, cause boost is with me.....
    85-Turbo-5 speed,BOV,FMI,15Psi,Mustang rims,
    87-Turbo-Automatic w/overdrive,LSD, Stock
  • #3
    The reason I installed a 20 amp fuse is because the wire that runs to the radio runs to a 15 amp fuse so I just added the other 5 amps for a 20 amp fuse. (not sure if that makes sense). I tried making the signal wire one piece but the stock length wasn't long enough to reach the signal wire in the engine bay so I had to solder on an extension piece so that it would reach. The ground wire is mounted to other ground wires directly to the body, and I hooked it to the radio wire for power because it called for a 12v power source that worked in both the ACC position along with the ON position for the key.

    I'll go over them one more time just to make sure.
    Bah-chicka-wow-wow
  • #4
    what year is your Z?
    Matte Black 86T - Sold
  • #5
    An 88, the ECU and motor are from an 86 though
    Bah-chicka-wow-wow
  • #6
    86 = Titania… Don't know if that is going to work man.

    Terrible idea putting those wheels on…
  • #7
    Why? Is it because of the material it's made of or because the wiring harness is different on the 88 body that doesn't allow the 86 ECU to read the 86 O2 sensor?
    Bah-chicka-wow-wow
  • #8
    Amadeus wrote: Why? Is it because of the material it's made of or because the wiring harness is different on the 88 body that doesn't allow the 86 ECU to read the 86 O2 sensor?
    It's because the sensor you have communicates to the ECU via resistance. The older ones communicate using voltage. Resistance will not make your AFR gauge to shit.

    I think thats right? There is a thread in the engine management section that talks about the different O2 sensors and which one puts out the resistance signal. You will be able to figure out if that is your problem if you go look at that thread. It should be stickied.

    Here it is.
    viewtopic.php?f=6&t=5451
    85 Z31 6.0 LSX turbo 766whp/792wtq
    04 GTO, LS6, big cam, porting, N20… underway for summertime daily driver.
  • #9
    Thanks Satan I'll give it a look over and see if that might be my problem.
    Bah-chicka-wow-wow
  • #10
    [quote]SATAN wrote:
    Originally posted by Amadeus
    Why? Is it because of the material it's made of or because the wiring harness is different on the 88 body that doesn't allow the 86 ECU to read the 86 O2 sensor?
    It's because the sensor you have communicates to the ECU via resistance. The older ones communicate using voltage. Resistance will not make your AFR gauge to shit.

    I think thats right? There is a thread in the engine management section that talks about the different O2 sensors and which one puts out the resistance signal. You will be able to figure out if that is your problem if you go look at that thread. It should be stickied.

    Here it is.
    viewtopic.php?f=6&t=5451
    The statement I underlined is not exactly how it works but it is the jist of it. For those curious you can read the link for yourself.
    85 Z31 6.0 LSX turbo 766whp/792wtq
    04 GTO, LS6, big cam, porting, N20… underway for summertime daily driver.