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Thread: 3sgte TPS reading one hundred percent FULLY CLOSED???

  1. #1
    Forum Member Grease Monkey
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    Default 3sgte TPS reading one hundred percent FULLY CLOSED???

    Hey all,

    As the title says... im absolutley bamboozled by this one...

    Just started to get my build running ok ish (its crazy rich fouling plugs still) and i noticed (standalone ecu) the TPS is reading a HUNDRED percent at idle when the throttles fully closed?

    Anyone ever encountered something like this?

    The TPS always used to read thirteen percent at idle even with the TPS mechanically disconnected which was odd?

    Called Toyota. Absolutley useless. They then put me onto a 2 a min 'technical' line. They were clueless too.

    Its a 4 wire TPS. Power (E2), Angle signal (VTA), Throttle closed (IDL), Ground (E2).

    Ive looked at the BGB but im still no wiser.

    Could it have gone bad???

    Many thanks again.

    Chris.

  2. #2
    Junior Member Backyard Mechanic jondee86's Avatar
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    Default Re: 3sgte TPS reading one hundred percent FULLY CLOSED???

    The TPS is now connected to your standalone ECU, so Toyota will not be able to help. You will need to refer to the ECU installation instructions for how to calibrate the TPS. Typically the procedure will be like this...

    LINK G4 PlugIn Installation Manual
    1. Connect a laptop/notebook PC to the ECU and connect to the ECU using PCLink.
    2. Under the Analog Channels menu, ensure that the correct An Volt channel is set to 'TPS (Main)'. Refer to
    the pin functions section of this manual for details.
    3. Under the 'Options' menu, select 'TPS calibration'.
    4. Follow the on screen instructions.
    5. Select the 'Analog Inputs' tab in the runtime values section of PCLink (lower part of the screen).
    6. Ensure the Throttle Position value reads 0% when the throttle is closed and 100% when fully open.
    7. Perform a 'Store' by pressing F4
    Cheers... jondee86

  3. #3
    Junior Member Backyard Mechanic jondee86's Avatar
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    Default Re: 3sgte TPS reading one hundred percent FULLY CLOSED???

    Just to elaborate a little... with a boosted engine the main load sensorwill be the MAP sensor. So the engine will run (not particularly well) with the TPS out of calibration, or even without a TPS at all. But the ECU uses the TPS information for acceleration enrichment, overrun fuel cut, ISCV enable etc., so you want to have it correctly calibrated.

    With your laptop connected and the ignition turned ON, you should be able to see the TPS percentage change as you press on the accelerator pedal. If the TPS is reading 100% when the throttle is closed it usually indicates that the wires are mixed up. Changing two of them around should fix that. However, if the the TPS reading does not change when you open the throttle, jumps around instead of increasing smoothly, won't hold the calibrated 0% and 100% points, or only works sometimes, then either you have a wiring problem or you need a new TPS.

    The fact that your TPS would read 13% when off the throttlebody is odd as I would have expected zero. Maybe the TPS was calibrated before it was installed on the throttlebody? It is common for the TPS arm to have to be rotated forward a bit against the spring when being fitted. This ensures it is active at rest rather than sitting against its internal endstop. Maybe that "preload" could be around 13%?

    Anyway, try calibrating and see if pressing on the accelerator gives you a nice smooth sweep from closed to open.

    Cheers... jondee86

  4. #4
    Junior Member Grease Monkey
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    Default Re: 3sgte TPS reading one hundred percent FULLY CLOSED???

    If you wire it wrong it can throw the scale out.

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    Forum Member Grease Monkey
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    Default Re: 3sgte TPS reading one hundred percent FULLY CLOSED???

    Quote Originally Posted by LittleRedSpirit View Post
    If you wire it wrong it can throw the scale out.
    Hey Jon/Littleredspirit,

    UPDATE...

    Thanks as always for the reply and help.

    Finally got to the bottom of it.

    Somehow water had got inside the tps??? My garage is super leaky but still dont fully know how.

    Put a fresh TPS on... lo and behold... runs like a beast again.

    Only thing is the plugs are still CONTANTLY fouling even tho the AFRs look reasonable.

    Can OLD fuel (6 months, its been diluted down several times recently with fresh fuel) foul out plugs even if the AFRs are ok? Eg not too rich?

    Cheers

    Chris

  6. #6
    Junior Member Backyard Mechanic jondee86's Avatar
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    Default Re: 3sgte TPS reading one hundred percent FULLY CLOSED???

    Quote Originally Posted by Blackcountryboy View Post
    Only thing is the plugs are still CONTANTLY fouling even tho the AFRs look reasonable.
    Plugs too cold? What plug and heat range are you using? A plug that might be great on a racetrack may not be so great for driving around town. If the ceramic does not get hot enough to burn off deposits it will collect carbon and then it is much easier for fuel fouling to occur.

    Cheers... jondee86

    PS: Maybe squirrels have been peeing on your TPS ?

  7. #7
    Junior Member Grease Monkey
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    Default Re: 3sgte TPS reading one hundred percent FULLY CLOSED???

    Glad its running mate. You might have too much cranking fuel, you might have too much transient enrichment, or you also might have positive fuel trim coming from somewhere under warmup conditions.

    From experience playing around, the cranking fuel volume only needs to be enough to get a good initial fire out of the motor, as a starter will spin the engine at approx 220 to 250rpm, so then you can experience your initial ignition of compressed fuel, which will then instantly speed the motor up above the cranking threshold that you set, mines about 350rpm.

    Once the engine speed jumps above your threshold its the fuel maps that control its running, so you might be super rich between cranking and idling speed in those maps, depending on your map resolution, it could simply be a couple rich map cells in there that throw up unexpectedly rich fuel. Since the engine doesnt spend time below idle speed under normal conditions its impossible to get the afrs for those map cells, its something you just have to play with and eliminate as a possibility.

    If some cylinders have more fouling issues than others you might have something causing uneven airflow, like a vac leak, coupled with a generally rich condition.

    Theoretically, if you were 20 percent rich and three cylinders had fouled plugs and the other didnt, I might suspect a vac leak in the unfouled cylinder and a general rich condition. it might average out on the sensor to an afr that looks reasonable, but you might be mixing random numbers from cylinder to cylinder, and without a thermocouple its hard to tell precisely. You could have three cylinders at 11:1 and once cylinder at 16.5:1 and you might see a decent afr in the logs.

  8. #8
    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Re: 3sgte TPS reading one hundred percent FULLY CLOSED???

    fouling or just sooty?
    plugs have to get hot to burn off the carbon (think Pyrolitic oven) . idle won't do it. needs an Italian tune or just normal road running (unless they are "cold" plugs, then need to be run harder to get them to heat up)

    as for AFRs, the AFR reading is just the sum of the residual oxygen in the exhaust.
    as said, even if wideband, just the right size air leak in the exhaust + pig rich cylinders, could look like good AFR
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