TPS adjustment and TB air screw on 95 GT?

Discussion in '1994 - 1995 Specific Tech' started by johnny_munyak, Jun 30, 2010.


  1. johnny_munyak

    johnny_munyak Member

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    I was checking my TPS today and found it was around 1.03 volts ( going to verify and compare with a second volt meter to be sure). Was going to adjust the TPS sensor, but I can't even get to the screws with the IAC valve in place on the the throttle body. I don't want to damage the screws by using an inappropriate screw driver or not getting a good bite on them. Not a big deal to remove the IAC valve, just wanting to know if that is common practice?

    Also, was checking the amount of turn on the TB air screw and it is at about 2.5 turns. From what I remember, this should not be above 2 turns. Adjusting it by 1/2 turn does make a difference. According to instructions I have, it should be betwee 1/2 and 2 turns max. If above 2 turns, adjust idle stop screw another 1/2 turn and readjust air screw until it is within those parameters.

    Does this sound right?
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  2. toyman

    toyman SN Certified Technician

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    The TB volts at 1.03 are well within the PCM's range (.65v - 1.25v) to determine the idle position. There is no magic position on the IAC screw. Just set it to maintain a steady idle. The idle stop screw should not be adjusted as it is factory set. It is set to be slightly open so as to ensure it doesn't bind in the throttle bore.
    #2
  3. Chythar

    Chythar Well-Known Member

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  4. HISSIN50

    HISSIN50 "How long does it take to get help in here? SN Certified Technician

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    FWIW: it's not uncommon to find that adjusting the idle bleed out more than about 1.5 turns creates a hanging idle.
    #4
  5. johnny_munyak

    johnny_munyak Member

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    I have an aftermarket 65mm Ford Racing throttle body and stock 70 mm MAF. Didn't bother changing it since it was recommended by many people that the algorithms with the stock MAF are the best you can get and the 70 MM flows more than enough for stock or even modified 302's.

    How many turns is the air screw adjustment effective......what's the limit.. 3-4 turns?

    As for the TPS voltage, it seems strange that even the instructions that came with the new TB before I installed it preached the 0.96-0.98 voltage setting?

    IF the ECM can compensate for any voltage as long as it falls between 0.6 and 1.25 volts, why are they so picky with the recommended .098 setting?
    #5
  6. Last5.0

    Last5.0 Active Member

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    From what I understand, the Fox ECUs didn't automatically zero out the TPS on startup like the SN's do and it was common to set it as close to just under 1 volt as possible.
    #6
  7. johnny_munyak

    johnny_munyak Member

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    Now that you mention it, I don't remember there being any slotted holes on the TPS sensor other than the limited play there would be around the screws holding it onto the TB.....
    #7
  8. Chythar

    Chythar Well-Known Member

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    The TPS discussion has been had several times before in the forum. Setting the TPS voltage is needed for 86-93 5.0's but not 94-95. Last5.0 is correct on the difference on the fox ECU's versus ours. However, setting the TPS voltage on a 94-95 is a myth that just doesn't seem to die.
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  9. HISSIN50

    HISSIN50 "How long does it take to get help in here? SN Certified Technician

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    Aero foxes baseline the TPS like our cars do.
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  10. johnny_munyak

    johnny_munyak Member

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    Yes, I've read it many times and actually have the full copy of the instructions you posted. I won't worry about the TPS setting.

    How many turns out is the air bleed screw effective before you should adjust throttle stop?
    #10
  11. final5-0

    final5-0 Mustang Master

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    Several things about setting idle on a 94-95

    First thing is ......
    many things are involved in providing a steady and smooth idle :crazy:

    several settings in the pcm
    spark
    temp
    isc
    btw ... vacuum ain't one of em :nono:

    RPM rate is done with the pcm N O T the mechanical screw on the side of
    the tb and it is N O T just like an old school carb :)

    Yes ... if one turns that screw to open the linkage more the idle speed will
    go up but that may hose up one or more of those many things we talked
    about above :(

    So ... like was said above ... the mechanical screw is for the purpose of
    keeping the tb blade from binding or sticking to the tb bore when the
    throttle gets snapped shut

    Like was said above ... you don't wanna try and adjust the tps :nono:

    As a matter of fact ... I can't tell you how many times I have seen
    uninformed folk hose up perfectely good working parts with their
    attempt to adjust the tps to .99 volts :bang:

    You see peeps drilling out holes and boggering up screws for
    absolutely nothing to be gained at all :doh:

    The screw under the rubber cap ......
    It can throw off the idle if it is out too far :Word:

    Bottom Line ... leave your tps alone as it is at this time

    One last thing ... if you go beyone a certain point with mods .........
    Mods like h/c/i and mostly a cam with a good bit of duration ...............
    Access to the pcm most likely will be needed for a ROCK STEADY
    idle just like a little stocker

    Grady
    #11
  12. R.J.

    R.J. Member

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    The above listed post #3 has a link to a procedure that has fixed many an idle and stalling issue for me. I have read many threads talking about how much TPS voltage does not matter (especially now that I own 2000 GT) but I would give that link a chance and see what kind of issues it can fix. For example: I put a TFS HCI kit with a bbk t-body on my buddies 94 GT and he had a horrible hot idle and stall issue. Guess what, an idle and TPS adjustment (above link) fix the issue. Just my .02!!
    #12
  13. machuginah

    machuginah New Member

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    idle adjustment is a case of "if it aint broke dont fix it" as it can open up a huge can of worms, but if you are having issues, disconnect your battery for a few minutes, then, set your idle with the car warm and the tps unplugged to whatever you want. Shut the car off and check that tps voltage isnt too out of range (over 1.25V) if its not then dont mess with it. Idle the car for 5 minutes, then run all accessories (a/c headlights etc) for another 5 and let the computer re-learn. and you're done.
    #13
  14. HISSIN50

    HISSIN50 "How long does it take to get help in here? SN Certified Technician

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    I think you meant to say IAC instead of TPS.
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  15. wytstang

    wytstang Mustang Master

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    Some good reading, enjoy.
    [​IMG]
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