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How do I adjust the TPS on an 87?

Discussion in 'The Garage' started by mtrdrms, May 24, 2005.

  1. mtrdrms

    mtrdrms 1/2 ton status

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    The instructions for my Holley TBI (BIG MISTAKE SO FAR) say to adjust the TPS to .65 volts. Any tips on how this is done? Thanks
     
  2. sled_dog

    sled_dog 1 ton status

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    stock TB is non-adjustable. Did the holley come with a new one? The way you normally adjust one is to hook up a volt meter to the leads(with power to the sensor, key on), loosen the bolts and swivel the sensor till you get the desired setting.
     
  3. mtrdrms

    mtrdrms 1/2 ton status

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    Yeah the Holley came with a new one. I will try that thanks.
     
  4. sled_dog

    sled_dog 1 ton status

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    stick some paperclips into the back of the plug. Its called backprobing, helps prevent ruining the connector by trying to jam your leads in there.
     
  5. mtrdrms

    mtrdrms 1/2 ton status

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    What leads do I hook the volt meter to?
     
  6. sled_dog

    sled_dog 1 ton status

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    how many wires are there on the sensor? Should be 3 I believe. One is a signal, one is signal ground(to the PCM) and one is Reference. Signal and Signal Ground are what you want to hook to. I can't say which is which. Should get a reading of between .something volts and 5V(WOT). I can look up the pin arrangements tomorrow or you could just try it. Your best bet is to just go for it. Hook them up to 1 wire at a time. Put the ground to a good ground of course. If you get a steady 5V(while moving the throttle) that is your reference and not what you are looking for. The other 2 wires will be what you want, hook one lead to each(unless your meter is junk it shouldn't really matter which) and start testing. Should be a very low if not nonexistent reading to begin with. Open to WOT and should be near 5V. Go ahead and adjust as needed.
     
  7. mtrdrms

    mtrdrms 1/2 ton status

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    I am getting nothing but my voltmeter is a POS! So I am going to ask you to bear with me here. I am going to start at square one. The TPS has 3 female leads and the connector has 3 male leads. My voltmeter has a red and a black wire. So should I be hooking the red adn the black to two of the leads on the TPS? I know you dont know which two but should I be hooking both voltmeter leads to both leads on the TPS?. Should I be in DC or AC? What should I be grounding? My voltmeter only has two wires (red and black). Sorry, I know I am an idiot but I am desperate here. Thanks alot for all of your help.
     
  8. sled_dog

    sled_dog 1 ton status

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    Alright I typed out the whole big thing on how to figure this crap out the hard way.... then remembered I have a service manual :crazy:

    Alright, first things first. Plug in the harness to the TPS sensor. It needs the voltage supply to operate and give you your readings. Now stick 2 paperclips in the back of the connector. Namely one in each hole that the wires go into. You should want the Dark Blue and Black wire(Dk Blu will be an outside wire, and Black will be the middle). "NOTE: make sure the key is off for this next step." If you have a multimeter, switch to Ohmmeter and check for resistance. If there is little, no, or even a fairly large amount of resistance, you did good. If you get an OL reading(out of limits) that means there is no continuity and you need to redo the paperclips to try and make contact. Blip the throttle a little to see if the numbers change(they should).

    Now go back to voltmeter, you are ready to test. Simply turn the key to the run position. Do not need to start it, just need the power supply. Hook your positive lead to the black wire, and your black lead to the Dark Blue wire. You should see a low voltage reading. Open the throttle some and see if your reading changes(it should).

    If you are all good to here, go ahead and adjust.

    I am not 100% if the wire colors will apply to you. If they don't I'm sorry. I have an 88-98 Service manual in my lap and I'm quoting what the schematics for an 88-95 Chevy has. I wish I had my service manual from one of my older rigs, but thats at home.
     
  9. sled_dog

    sled_dog 1 ton status

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    Does anyone know another method to help this guy out? I explained the way I would(and have) do it, but it would seem to me Holley wouldn't just throw this setup at people and tell them to do it. Though I guess they very well could.
     
  10. shane74

    shane74 1/2 ton status

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    It's not that hard to do. Basically, figure out which wire is ground, (should be black) and then which wire is getting signal voltage (which wire gives you a variable reading as you move the throttle cable. It should read from .65 volts at idle to 5-6V WOT. Rotate the TPS until it reads .65 volts and screw it down. IIRC, you can bolt it on and be in the range it needs to be. Also, the stock ones are adjustable. They have just enough play in the bolt holes adjust the setting.

    I just did this a couple weeks ago. It took me all of 3 minutes to do it. You have to figure out which wires give you the variable reading as you move the throttle linkage from idle to WOT.

    IMO, the stock TBI unit is better than Holley, unless your stock unit is shot. It isn't wortht the $$ for the "upgrade".
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    If I didn't have a scanner I'd stop by Autozone and have them let me use theirs. You can watch the TPS voltage while you adjust it. Lot easier than paperclips etc., but you've gotta have a scanner handy to do it. :)
     
  12. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Talking to someone off-line and they mentioned that since you are having trouble with how to use the meter, you may not have realized you need to set it to *DC* Voltage rather than AC. The black lead from your meter needs to go to ground in some convenient place, usually best to use an alligator clip or jumper wire so you can set it and leave it there. Then the red meter wire is used to "back probe" the connector. As already stated, with the key "ON" (but the motor not running) one wire will give you nothing, another will give you a full 5V (or very close), and the other will give you something around half a volt. That wire with the lowest voltage is the one you want to be monitoring. Good luck.
     

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