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My rex hates TPS sensors

Discussion in 'Civic and CRX - EF' started by Periculum, May 11, 2008.

  1. Periculum

    Periculum Senior Member

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    I have a ZC in a 91 CRX HF. Even before the swap, I had issues with the motor bogging down randomly. The simple way to solve the problem was to unplug the TPS and all the issues went away (minor loss of power for obvious reasons). I've replaced the TPS sensor and measured it at both the TPS itself and the ECU. At the sensor it measured exactly .5v (at close) and at the ECU it measured .15-.2v less than the sensor. I was told that the .2v loss is insignificant.

    I've had to unplug my new TPS because my car behaves the same way with the new sensor as it did with the old. My only guess would blame the issue on something in the wiring. I have even used two separate ECUs to see if one was faulty (Si and Integra).

    I have checked and double checked my installation of the sensor. I have measured it several times at the sensor and the ECU. The sensor reads fine and doesn't throw a code, but car isn't capable of getting the proper air/fuel ratio when its cold or when shifting into another gear.

    Anyone else have something like this before? or have any ideas on what else I should check?
     
  2. dacheat

    dacheat ..is grounded.

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    in for the read.
     
  3. YBLEGAL

    YBLEGAL Regular Member w/ Cheese

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    i would run a seperate signal wire from the tps to the ecu.

    it sounds like there's some extra resistance in there someplace that should not be. .2 is enough to allow more air past than it thinks. i know from adjusting my own tps tons of times that there is a large difference in how the motor runs between .5v and .3v closed throttle. it should not be losing voltage like that between the sensor and ecu. make sure the voltage increases at a somewhat smooth rate, with no abnormal voltages when opening the throttle. also check that your getting 4.9~5v to the TPS. if your getting the 5v ok, extend a wire from the 5v lead of the TPS harness plug to the right lead on the sensor. then connect the signal lead of the TPS directly to the ECU with a new, seperate wire.

    hope that helps
     
  4. Periculum

    Periculum Senior Member

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    I had thought about "wire jacking" another wire that is no longer in use for the purpose you have mentioned.

    The progress on the TPS is very good. Much harder to adjust this TPS into place than an older one, because of how sensitive it is.

    Which wire is the one to check for the voltage going TO the TPS?

    I did check the closed voltage with the motor on, but I wasn't sure that would have any useful information. It was .26v at the TPS with the car running (no throttle). I thought that was odd.
     
  5. YBLEGAL

    YBLEGAL Regular Member w/ Cheese

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    they should be the same sensitivity. it's the only way it would work.

    by progress i'm guessing you mean the smoothness at which the voltage increases as the throttle is rotated open? just wanting to be clear.

    you'll want to adjust it with the voltmeter connected to .5v closed throttle. wide open throttle should get to about 4.5v.

    i'm not sure which color wire it is on your CRX. you can test all of them (should be red i believe; most familiar with my OBD1, sorry)
     
  6. Periculum

    Periculum Senior Member

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    Yeah the smoothness is just fine. nothing unusual there. I did set the car to .5v closed throttle with the car off. (key in on position)
     
  7. YBLEGAL

    YBLEGAL Regular Member w/ Cheese

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    ok did you try the signal wiring bypass i suggested? dont use another wire as your 'wire-jack' method suggested. run a brand new line that you know 100% is not damaged in any way.
     
  8. Periculum

    Periculum Senior Member

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    Not yet, gonna fool around with it a little bit tomorrow. Just not sure exactly where that whole bunch of wires makes it through the wall.... I should know that by now.
     
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