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Thread: TPS Idle Switch

  1. #1
    Altia ER34 GTT Domestic Engineer JetspeedCamry's Avatar
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    Default TPS Idle Switch

    Hey everyone!

    I just wanted to know, what the IDLE switch inside the TPS is for. Obviously, it tells the ECU when the throttle position is at idle, but what exactly does the ECU do after it recieves this signal. Would the engine die if this signal wasn't there?
    Long story short, the engine used to run an automatic transmission, and now runs a manual. Everytime i let of the pedal, just at the last few mm's of throttle plate movement, the ECU dumps fuel in, which makes a nice little jolt. I wanted to try to remove this, so letting off the accelerator has a smoother transition, and the exhaust doesn't knarl @ 0% TPS. At around 0.1-0.2>% all is good, its just that last little bit, which i assume is the IDLE switch inside the TPS. I beleive it is easy to adjust, since you just turn the TPS anticlockwise a touch, so it doesnt trigger it.

    Any suggestion/info would be appreciated.

    Thanks!
    Kind Regards,
    Kurt.

    1998 ER34 ニッサン スカイラインGT- T
    RB25DET 5 Speed Manual | Blitz SE Return Flow FMIC | Greddy Profec II Spec B BC | Apexi N1 Turbo Back Exhaust

  2. #2
    Not a patch on a Backyard Mechanic
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    Default Re: TPS Idle Switch

    The IDL switch in the TPS - also called a Closed Throttle Switch produces a 0 volt signal to the ECU, so it knows that it is at idle. As soon as the throttle is cracked open, the ECU will get reading +B voltage and delivering fuel to the injectors to suit.
    I am the very last guy to ask about adjusting the TPS :-)
    RA23
    1G-GZE

  3. #3
    Altia ER34 GTT Domestic Engineer JetspeedCamry's Avatar
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    Default Re: TPS Idle Switch

    Hmm interesting. To give an idea of what the engine sounds like, refer below haha

    SOUND: BMMMMMMMMMmmmmmmmmm................BRRRRRRRRRRRblu blublub...........
    TPS:......10%...............5%............2%...... ...1%..0.2%..0%......................^ 1200RPM...^ idle


    If that makes sense

    It feels like as soon as the switch is engaged, fuel is dumped in...and it makes the engine jolt sometimes. The torque of the engine is trasnfered very "sharply" at that small percentage of TPS movement.

    So not allowing the IDL switch to be tripped, by adjusting the sensor, would effectively ???
    Last edited by JetspeedCamry; 14-03-2006 at 12:15 PM.
    Kind Regards,
    Kurt.

    1998 ER34 ニッサン スカイラインGT- T
    RB25DET 5 Speed Manual | Blitz SE Return Flow FMIC | Greddy Profec II Spec B BC | Apexi N1 Turbo Back Exhaust

  4. #4
    Altia ER34 GTT Domestic Engineer JetspeedCamry's Avatar
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    Default Re: TPS Idle Switch

    Bumpety! Anyone?
    Kind Regards,
    Kurt.

    1998 ER34 ニッサン スカイラインGT- T
    RB25DET 5 Speed Manual | Blitz SE Return Flow FMIC | Greddy Profec II Spec B BC | Apexi N1 Turbo Back Exhaust

  5. #5
    Toymods V8 Member Too Much Toyota CrUZida's Avatar
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    Default Re: TPS Idle Switch

    If the TPS does not go to IDL, then the ecu will not default to the idle fuel/timing map, and the ISCV will not operate correctly.

    Get a multimeter out, find out which pins are IDL and E2, and adjust the TPS so it switches as soon as the throttle is cracked.
    Peewee
    1985 MZ12 Soarer - 1UZ Powered
    2013 86 GTS

  6. #6
    Altia ER34 GTT Domestic Engineer JetspeedCamry's Avatar
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    Default Re: TPS Idle Switch

    Yep, tested it and all, works perfect. Continuity @ 0.30mm and No-continuity @ 0.70mm.
    However, the car has the "jolt" as explained above, and i was thinking it may have something to do with that swtich. I figured though, that, if the switch wasn't trigger, the car wouldnt idle properly. Bugger.
    Kind Regards,
    Kurt.

    1998 ER34 ニッサン スカイラインGT- T
    RB25DET 5 Speed Manual | Blitz SE Return Flow FMIC | Greddy Profec II Spec B BC | Apexi N1 Turbo Back Exhaust

  7. #7
    My Wife says I have Too Much Toyota o_man_ra23's Avatar
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    Default Re: TPS Idle Switch

    It says in your signiature that you have a powerchip installed. If this is so, then it would be mapped to allow for an auto (which have a constant drag at idle). As such, maybe you should look at getting this re-programmed to suit the manual. This should easily be modified with software, and a good performance shop should be able to supply a ready made map for your setup.

    Cheers, Owen
    Cheers, Owen
    1977 RA28 with 1JZ-GTE (Was 18R-GTE)
    Lancer EVO Brakes into old Celica/Corolla/Corona
    Doing the things that aren't popular... cause being popular and being good are often distinctly different.

  8. #8
    Junior Member Backyard Mechanic 3sgte's Avatar
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    Default Re: TPS Idle Switch

    I did an auto to M/T conversion on an old 4AG (vane AFM type), I needed to swap the Circuit opening relay for one with a capacitor to prevent the fuel pump shutting down on closed throttle. (M/T vehicle circuit opening relays for Vane type AFM cars have the capacitor.)

    The flap in the AFM controls the circuit opening relay, and inertia of the flap closing on closed throttle can cause it to disengage the circuit opening relay.

  9. #9
    Altia ER34 GTT Domestic Engineer JetspeedCamry's Avatar
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    Default Re: TPS Idle Switch

    o_man_ra23:
    Yeah i was thinking this also. I was going to bump the lower end down a few notches. I too thought this may be a problem.

    3sgte:
    Mmm. Interesting. Ive never heard of that before. Are COR's interchangable between cars? Or vehicle specific? This car wasn't available in manual, so finding a M/T COR for it specificly would be impossible !
    Kind Regards,
    Kurt.

    1998 ER34 ニッサン スカイラインGT- T
    RB25DET 5 Speed Manual | Blitz SE Return Flow FMIC | Greddy Profec II Spec B BC | Apexi N1 Turbo Back Exhaust

  10. #10
    Junior Member Backyard Mechanic 3sgte's Avatar
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    Default Re: TPS Idle Switch

    Quote Originally Posted by JetspeedCamry
    o_man_ra23:
    Yeah i was thinking this also. I was going to bump the lower end down a few notches. I too thought this may be a problem.

    3sgte:
    Mmm. Interesting. Ive never heard of that before. Are COR's interchangable between cars? Or vehicle specific? This car wasn't available in manual, so finding a M/T COR for it specificly would be impossible !
    In my case, I just wired it up to suit.

    I have an EWD for a 1990 MY, and it shows a capacitor in the Circuit Opening Relay.
    Hope I haven't wasted your time. You could always pull the top off yours, and see if there is a capacitor inside. Alternately, monitor either the power supplied to the fuel pump, or fuel pressure to confirm/deny this problem.

    They had a V6 MT in North America, VZV21L-UEMDKA, assuming that I haven't misunderstood the model you are speaking of.

    Does your throttle body have a vacuum type throttle positioner on it? One that kicks the idle up a notch if its vacuum hose is disconnected? If so, this might be another approach to a workaround for your problem.

  11. #11
    Altia ER34 GTT Domestic Engineer JetspeedCamry's Avatar
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    Default Re: TPS Idle Switch

    Wasting my time!?? No way. Its all very interesting!

    Yeah ive heard of the NT V6-MT's but there so hard to find parts from. Ive asked around for ECU's from them (before i thought it was a bad idea) and nilch. There were next to none in yards that i contacted, and if they were there, were stripped down to just shells.

    Ill have a look at the COR and see if theres a cap in there. Wonder how hard it would be to add one.

    Im not sure what you mean but the "vacuum type throttle positioner".
    Its got an Idle Air Contoller, which is a stepper motor type unit. It has vacuum ports on the top of the TB (3 of them). If i disconnect a direct manifold vacuum line somewhere, the idle does raise a bit yes, by about 100 or so RPM. Is that what you mean?

    Your help is appreciated. Quite helpful
    Kind Regards,
    Kurt.

    1998 ER34 ニッサン スカイラインGT- T
    RB25DET 5 Speed Manual | Blitz SE Return Flow FMIC | Greddy Profec II Spec B BC | Apexi N1 Turbo Back Exhaust

  12. #12
    Junior Member Backyard Mechanic 3sgte's Avatar
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    Default Re: TPS Idle Switch

    If present, it is a little vacuum diaphragm with a mechanical plunger/link that physically opens the throttle plate a slight amount if vacuum is not present.

    It looks like a little version of a vacuum advance that would be found on an old distributor.

    You can see one at the top left of this picture:
    http://www.off-road.com/toyota/tech/...ebody/0604.jpg

    This one:
    http://homepage.ntlworld.com/nick.ch...h/jr/tube1.jpg
    has a Vacuum Transmitting Valve that allows vacuum to pass through easily in one direction, but allows vacuum to pass through slowly in the other direction, causing the throttle to close slowly after it is released.

    If installed in the correct direction, this valve causes the idle speed to drop more slowly after the throttle is closed.

    It would be connected to a vacuum port on the throttle body, not manifold vacuum. Vacuum would be present at this port with the throttle nearly closed, but vacuum would not be present if the throttle is open say 20%.

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    Default Re: TPS Idle Switch

    Quote Originally Posted by JetspeedCamry
    Yep, tested it and all, works perfect. Continuity @ 0.30mm and No-continuity @ 0.70mm
    I have not got the answer to your problem, but just don't mess with your TPS, as you have said above, it works fine. Something else will be causing the problem you are having. I have effed around with my TPS and only made things worse...
    RA23
    1G-GZE

  14. #14
    Altia ER34 GTT Domestic Engineer JetspeedCamry's Avatar
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    Default Re: TPS Idle Switch

    Quote Originally Posted by 3sgte
    If present, it is a little vacuum diaphragm with a mechanical plunger/link that physically opens the throttle plate a slight amount if vacuum is not present.

    It looks like a little version of a vacuum advance that would be found on an old distributor.

    You can see one at the top left of this picture:
    http://www.off-road.com/toyota/tech/...ebody/0604.jpg

    This one:
    http://homepage.ntlworld.com/nick.ch...h/jr/tube1.jpg
    has a Vacuum Transmitting Valve that allows vacuum to pass through easily in one direction, but allows vacuum to pass through slowly in the other direction, causing the throttle to close slowly after it is released.

    If installed in the correct direction, this valve causes the idle speed to drop more slowly after the throttle is closed.

    It would be connected to a vacuum port on the throttle body, not manifold vacuum. Vacuum would be present at this port with the throttle nearly closed, but vacuum would not be present if the throttle is open say 20%.
    Yeah, my TB doesn't have anything like that on it. On the NT V6's with manual tranny, they have something called a "dashpot". Im not 100% sure what it does, but it attatches to the throttle in some way, and has a vacuum line or to connecting to it. Any idea what that is for? Its specific to only MT version in US.

    Quote Originally Posted by ra23celica
    I have not got the answer to your problem, but just don't mess with your TPS, as you have said above, it works fine. Something else will be causing the problem you are having. I have effed around with my TPS and only made things worse...
    Hehe, yeah, the last thing i want is to stuff something! So i think ill just leave it alone. There must be another way to fix this problem, and as stated, im doubting too that the idle switch is the problem.
    Kind Regards,
    Kurt.

    1998 ER34 ニッサン スカイラインGT- T
    RB25DET 5 Speed Manual | Blitz SE Return Flow FMIC | Greddy Profec II Spec B BC | Apexi N1 Turbo Back Exhaust

  15. #15
    Junior Member Grease Monkey
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    Cool Re: TPS Idle Switch

    IDL simply lets the ECU know the tps is in the "idle specification" for the life of the unit.
    The fuel pump & fuel system (in any Denso AFM system) is turned on & initiated by the contact switch in the AFM.
    In this picture (A generation II, large body Denso AFM), the fuel pump switch is located just to the right of the left most screw, roughly half way up the AFM. As the middle rotating assembly rotates with airflow. The metal arm by the screw is rotated away from two thing, straight, spring pieces of metal that have a contact between them.

    Airflow during cranking moves the assembly enough to let the contacts move together, closing the circuit & turning the fuel pump relay on.


    Making AFM Denso setups (Not just Toyota... Several OEM's used identical construction Denso components.) very easy to troubleshoot fuel-wise. Push the flap, the fuel pump turns on.


    It is relatively uncommon in the car circles for that TPS sensor to go out-of-adjustment. On the other hand, the identical part is a fairly common cause of both poor idling & general performance in other circles. (I.E. People on TN don't know to look at the TPS to cause such problems because no one has ever suggested it... So you've never heard of it being a problem. heh... right then) I would adjust it slightly, but don't rely completely on it. Try another TPS unit after an ECU reset. Most piggybacks will try to avoid tuning idle unless necessary, as it can be a very hairy experience. However, checking it would be prudent.
    If your AFM cog is too loose... Idle problems. I would return it to stock & reset the ECU to see if it's better.


    Lastly... If a TPS Drill the AFM Bypass screw plug off & begin to adjust the AFM bypass screw. Be damn sure to keep refference on where you have rotated it. You can test this by swinging the AFM cog richer & leaner to determine how the A/F ratio is off & what your corse of action should be.



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