Adjusting your TPS to 0.98v is NOT necessary

Discussion in 'Fox 5.0 Mustang Tech' started by Mustang5L5, Oct 17, 2010.

  1. Seems to be a common myth, so lets sticky a thread explaining how the TPS works. Jrichker has provided the basic TPS guideline to follow. I'll just preference it with this.

    Adjusting your TPS to .99999999 volts is not necessary at all. There is a general range the computer will accept as idle voltage for the TPS. This range is 0.5 - 1.1 volts. ANYTHING within this range is acceptable. If idle voltage is outside this range, a TPS code is generated by the computer.

    Therefore, the only adjustment really necessary is to verify the tps voltage at idle is anywhere between the above range. If this is a FORD OEM tps, it should be. Aftermarket TPS's might be different and require you to slot the holes to get it in range. If it is in range, then you are fine. No need to chase the mythical 0.99 volts that has been tossed around for years. Upon vehicle startup, the computer will take the base idle voltage, and apply 2.71v to that number as the trigger point for WOT operations.

    To make a long story short. If your idle TPS voltage is anywhere between 0.5V and are good to go.

  2. Thank you for this post. Every ford publication has told me this and even my chilton, but everyone on the internet seems to say it's the mythical .99volts that you're suppose to have it set at. I was wondering if people knew something I didn't
  3. Good post, Mike. People seem to think the TPS is some magical sensor that can make or break performance if you don't have it set exactly right (0.9999999999999999999V).

    I'm adding this one to the "Really Common Questions" sticky over in Talk! Feel free to remove this post if you want to keep this sticky cleaned up, you won't hurt my feelings. :nice:
  4. Added more tech data. Hopefully any tps questions can be directed here
  5. I adjusted my tps to the correct value now I'm getting code 85. Is this normal at 1.4v I get no code. Any lower I get code 85 please help.
  6. Code 85 has nothing to do with the TPS. Any relation to code 85 and what you do with the TPS is pure coincidence. Go back and work your way through the TPS troubleshooter at the beginning of this post.

    Code 85 - CANP solenoid - The Carbon Canister solenoid is inoperative or missing. Check vacuum lines for leaks and cracks. Check electrical wiring for loose connections, damaged wiring and insulation. Check solenoid valve operation by grounding the gray/yellow wire to the solenoid and blowing through it.
    The computer provides the ground for the solenoid. The red wire to the solenoid is always energized any time the ignition switch is in the run position.
  7. Thank you jrichker. Did just that and found the a crack in the line by the canister. I replaced it with a hose union. Problem is fixed.
  8. I'm new to the site but I have read this on many other sites.
    Well I checked mine and it was at 1.48v.Before I adjusted it wouldn't idle when cold for the 1st min and when it was warm it'd idle at 1000-1100 RPM.Also your eyes would begin to melt after a 1 min in the garage from it running so rich at idle.
    After adjusting it to .93v cold the cold start idle was help to keep it running.The RPM's came down to around 750 when warm and now your eyes only want to melt after about 5 min of idling in the garage.

    To me I believe it is very important to make sure it's with in range.

    I wondering tho,is it the EEC adds 2.71v for WOT to the .93v = 3.61v or is it in WOT at 2.71v?
    My base is .93v and with the throttle wide open I'm getting a 4.53v reading.Should it be this high?

    This is all measured from the green and black wires on the TPS.

  9. It's 0.93 + 2.71 = 3.61. So as soon as the voltage hits 3.61, the computer assumes you are at wot (or pretty close to it and adjusts timing/fuel accordingly). Of your idle voltage was 1.00, this number would now be 3.71.

    Anything beyond that makes no difference. Once you are over that voltage, you are technically wot and going to 4.5v makes no difference. It's normal

    But yes, at idle, the voltage needs to be somewhere in the 0.5-1.1v range. But hunting for a specific number is not necessary. Last time I checked my voltage, I think it was set about 0.76v or somewhere in that range.

    Adjusting the tps with the car running will always change the way it runs. After all, the engine has been started and the computer thinks you are manipulating the throttle and is adjusting air/ the engine will run a little stronger as you advance. When you shut the car down, everything you did flies right out the window pretty much
  10. OkThx

    This was all done with just the switch on but with the car cold.Because there is a slight diff in volt readings when it's hot to cold.
  11. It's a good thing it doesn't matter. I tried to get mine to .99 and the best I could do was .94 or something. I said FI and left it there. It idles and runs fine like that.
  12. This is one of the best posts I've seen on this's too informative..thanks.
  13. So I adjusted the tps, and it is sitting ~0.806V....

    But I am still idling around 1100rpm and I can't get it to go down....

    Also, I currently have only one vacuum line going to the carbon many should there be?
  14. If there is no TPS code, you don't have a issue with TPS

    2 vac lines to the charcoal canister. One line to the gas tank, and the other line into the intake manifold up front
  15. I once tried this myth but.. The bolt holes wouldn't line up when it was reading .9 volts
  16. back in the day we all used to open up the holes on the TPS because you HAD to get the voltage to 1. lol Then people realized the cars ran fine as long as it's within a range. I think they used to sell a device that was TPS adjuster or something like that- like the MAF voltage adjuster when you swapped out injectors and MAF''s.
  17. I was getting a TPS code. So I got the TPS to read 0.806V and then disconnect the battery for 15mins....and still high idle. Not as bad though. It was continuously around 1500rpm, now it might hit 1500rpm, but stays around 1100rpm for the most part.
  18. You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix. :D

    It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 134,000 hits, which indicates it does help fix idle problems quickly and inexpensively.
  19. I am getting 2 volts on the orange wire and .35 volts on the green wire. I assume my TPS needs to be replaced. I have been through the rest of the crank/no start checklist and am down to this. I have spark and fuel pressure, but no fuel in the cylinders. I replaced the distributor so PIP is new. The failure was catastrophic with no warning. There was a bit of a rough idle before the problem occurred. I have a 92 5.0 with about 25,000 original miles and no mods.