As it was running it died.. now does not run unless throttle is part open

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  1. #1
    Junior Member LancesMKII's Avatar
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    As it was running it died.. now does not run unless throttle is part open

    Hey CeliSup Community! [Car back story] [1984 P-Type] The car was running, after 8 years of sitting and one year of elbow grease, smogged, ran and idled smooth.

    I was driving down the freeway on a very hot Northern California sunny day, when I decided to pull off to exit, I down shifted and let the engine coast from 5k rpm down to a stop. When the vehicle came to a stop the engine stalled. I was unable to get the car to start or even move without keeping my foot on the gas. Sadly, on that Friday, through traffic, I tippie toed that throttle alllll the way home.

    Now the car sits. It still does not start without partial throttle input. How can a running car just quit on me? I checked the ISCV and it is receiving B+ voltage and the coil winding are within ohm spec @ 21ohms each. The TPS had a bad connector and a loose [Brown] wire. I think that one was sensor ground, E2, I may be wrong. I replaced the TPS and connector. The TPS is a 3 wire sensor. It's been adjusted to open circuit between IDL and E2 while 0.9 mm is between the stop screw. The distributor has not been removed since it was smogged, so we can rule out "set out of time", and the pick up coil resistence is ok.

    I can name other things that I went over but in short electrically it seems sound. I even went full crazy and threw parts at it. Replaced the AFM (tested used part) and fuel pressure regulator. I dont know where to look next other than the ECU.

    Thoughts and prayers? Lol thanks.

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  3. #2
    Boosting Mod SilverMk2's Avatar
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    ECU is the last thing I'd replace. Have you checked the basics, proper fuel pressure, have spark on all cylinders, timing so on and so forth?

  4. #3
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    Do the simple things first.

    You can also troubleshoot for rough idle or stalls by...
    1. Check spark plugs faulty
    2. Check for incorrect ignition timing (adjust back to 10 degree with a timing light)
    3. Check for ignition problem (a. ignition coil, b. igniter, c. distributor)

    If the engine starts with the accelerator pedal depressed, then the problem might be the ISC system. Once again, do the easy thing first. Check the fuse and the main relay number 1 for the ISCV. Second check the ISCV and it's wiring connection. Using a volt meter with the key in ignition on position, go to the ECU and check the ECU and the terminal connector. Make sure there's at 9-14 volt between ISC1 and E1, ISC2 and E1, ISC3 and E1, ISC4 and E1. Check that there is a voltage between ECU terminal +B and body ground. If bad, then considering repair or replacing the ECU.

    Lastly, you can also remove the ISCV from the car and then check the resistance between B1 and S1, B1 and S3, B2 and S2, B2 and S4. Make sure they are 10-30 ohm. Then applied a voltage to make sure the the ISCV moves in and out. To do this, apply a negative voltage in this sequence to S1, then S2, then S3, then S4 and then back to S1 while applying a positive voltage to B 1 and B2. While to see if the center plunger moves out. Repeat this in the reverse order to move it back in.

    B1 and B2 is the plug with the two terminals.

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  6. #4
    CelicaSupra.com Member supraz's Avatar
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    Quote Originally Posted by Tarzanboy View Post
    Do the simple things first.

    You can also troubleshoot for rough idle or stalls by...
    1. Check spark plugs faulty
    2. Check for incorrect ignition timing (adjust back to 10 degree with a timing light)
    3. Check for ignition problem (a. ignition coil, b. igniter, c. distributor)

    If the engine starts with the accelerator pedal depressed, then the problem might be the ISC system. Once again, do the easy thing first. Check the fuse and the main relay number 1 for the ISCV. Second check the ISCV and it's wiring connection. Using a volt meter with the key in ignition on position, go to the ECU and check the ECU and the terminal connector. Make sure there's at 9-14 volt between ISC1 and E1, ISC2 and E1, ISC3 and E1, ISC4 and E1. Check that there is a voltage between ECU terminal +B and body ground. If bad, then considering repair or replacing the ECU.

    Lastly, you can also remove the ISCV from the car and then check the resistance between B1 and S1, B1 and S3, B2 and S2, B2 and S4. Make sure they are 10-30 ohm. Then applied a voltage to make sure the the ISCV moves in and out. To do this, apply a negative voltage in this sequence to S1, then S2, then S3, then S4 and then back to S1 while applying a positive voltage to B 1 and B2. While to see if the center plunger moves out. Repeat this in the reverse order to move it back in.

    B1 and B2 is the plug with the two terminals.
    +1 on this

    https://youtu.be/Vngp6WB_ai8
    This is the sound of the ISCV opening when you turn the engine off.

    The ISCV is stepped by grounding the coils sequentially. +12V is applied to one side of all four coils and then the ECU grounds the other side of each coil in turn to open or close the valve.

    When the engine is shut off, the ECU opens the valve fully by stepping the coils 255 times (If I recall correctly). This ensures that the next time the motor is started the valve is open so the car can start without having to open the throttle with the pedal. The valve is clutched so that it does not matter where the valve is when shut, it still steps 255 times.

    When I bought my wife's car, the ISCV did not work and I had to step on the throttle to start the car. In my case it ended up being the ECU. I could not hear the stepping sound. I did what Tarzanboy is suggesting while the ISCV was on the car. I left the +12V connector attached to the ISCV, disconnected the other plug on the ISCV and manually sequentially shorted the coils to ground. It took a while but it opened enough to allow the car to idle on it's own. The TPS must be correctly adjusted otherwise the ECU does not know the car is supposed to be idling and it will not adjust the ISCV position.

    http://www.cygnusx1.net/supra/Librar...aspx?S=FI&P=60
    Online TSRM page FI-60


    Dale
    Black 1983 P Type 5 Spd, Cloth Interior, BBK,HRE 17" Wheels, HKS Exhaust
    White 1984 P Type Auto, Leather Interior, Sunroof, Digital Dash

  7. #5
    Junior Member LancesMKII's Avatar
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    I am a complete butthead.... I've fixed this problem a bit ago and forgot to reply. It was a simple hole underneath the intake piping. The AFM wasn't bolted down, so the intake piping was bumping a bolt from the exhaust heat shield. It popped a hole in the intake underneath and that was all she wrote. Lesson learned. Always THROUGHLY check the basics.
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