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Thread: Idle sporadically jumps to 2000 RPMs

  1. #11
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    Quote Originally Posted by NckT View Post
    Cate to enlighten where the thermister is in the Lambda circuit? The only temperature dependant element I know is the temp switch, which is nothing to do with idle control and this does not effect idle, just the duty cycle for the frequency valve.

    You've got to be careful with your past as some may interpret what you've put as a means of covering up the fact you made a mistake in a previous post.
    No problem. I will refer you again to the Workshop Manual D:05:02 fig 38 for the thermistor for the idle circuit and D:04:11 fig 31 for the thermal switch in the Lambda system. Easy to confuse the two switches. I haven't checked but it may be possible to mix them up and hook each other's wire to the wrong one too. While they look similar and are supposed to operate at the same temperature, they have different part #'s. I don't know the consequences of mixing them up.
    David Teitelbaum

  2. #12
    Senior Member NckT's Avatar
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    David, I was being a bit facetious. The thermister is basically varying resistor in relation to temperature (ie NOT is switch) and is a 2 pin connector. The lambda switch is digital ie on or off and is a 1 pin connector on the switch ie a blade connector. You cannot physically get them swapped over by accident.

    In addition, Rob Grady is correct in both responses and the air to fuel ratio (mixture) will become richer with the frequency valve disconnected, not leaner.

    At the end of the day the op had resolved his issue, which is great news.
    Last edited by NckT; 04-14-2018 at 01:05 PM.
    RIP Rob van de Veer Top bloke

    I say Sir, I must be mad, one loves fixing K-Jet !

    Make sure there's plenty in the tank for the weekend chaps....

  3. #13
    Administrator Ron's Avatar
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    Quote Originally Posted by David T View Post
    No problem. I will refer you again to the Workshop Manual D:05:02 fig 38 for the thermistor for the idle circuit and D:04:11 fig 31 for the thermal switch in the Lambda system. Easy to confuse the two switches. I haven't checked but it may be possible to mix them up and hook each other's wire to the wrong one too. While they look similar and are supposed to operate at the same temperature, they have different part #'s. I don't know the consequences of mixing them up.
    Fig 38 shows the right location for the thermistor but pictures the lambda thermal switch.
    Hard to hook up wrong -- The plugs are different, single large spade vs two smaller spades.

  4. #14
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    Quote Originally Posted by villevol666 View Post
    Thanks everyone. After reading the manual, I went through the entire system. The ECU and all of the wiring is fine. Turns out the problem was the spring around the throttle control. It has seen better days! For now, I have just extended the screws a little bit to compensate. Will replace as soon as possible.

    Thanks again everyone!
    Wow that is one weak throttle spring! Idle spring/rod adjustment issues don't usually leave the idle that high. FWIT we have a 10% stronger spring available at about $10- less than the NOS cost.
    It is a little pricey either way but it's not worth risking damage or an accident on a $30- part.
    Rob

  5. #15
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    Quote Originally Posted by NckT View Post
    David, I was being a bit facetious. The thermister is basically varying resistor in relation to temperature (ie NOT is switch) and is a 2 pin connector. The lambda switch is digital ie on or off and is a 1 pin connector on the switch ie a blade connector. You cannot physically get them swapped over by accident.

    In addition, Rob Grady is correct in both responses and the air to fuel ratio (mixture) will become richer with the frequency valve disconnected, not leaner.

    At the end of the day the op had resolved his issue, which is great news.
    Thanks Nick but I was just trying to let David be right for once even though he was wrong lol!
    Rob

  6. #16
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    Quote Originally Posted by PJ Grady Inc. View Post
    Thanks Nick but I was just trying to let David be right for once even though he was wrong lol!
    Rob
    I may not always be right, but I am never wrong! (As long as we are being factious!). As for the A/F ratio, if the motor was running well and was properly adjusted, losing the Lambda system and the frequency valve, the mixture will be leaner. The Lambda system adds fuel to the leaner, base mixture to get to the right A/F ratio. That's why, when the system doesn't work properly (or not at all) the first impulse is to adjust the mixture screw to enrichen the A/F ratio. Another reason commonly used to mess with the mixture screw is to overcome vacuum leaks which lean the mixture.
    Last edited by David T; 04-14-2018 at 05:52 PM.
    David Teitelbaum

  7. #17
    Administrator Ron's Avatar
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    I have to agree with David WRT disconnecting the FV making it leaner -- Current through the FV decreases the pressure in the FD lower chamber......

  8. #18
    Member gullwinger's Avatar
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    Freq valve is controlled by the WUR and the WUR (warm up regulator) is controlled by a thermistor under the intake. There is a vacuum line under the WUR on the right side see if it has air coming out of it at idle. If so clean the screens on the WUR. The freq valve adds more fuel to the distributor when the car is cold.


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  9. #19
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by Ron View Post
    I have to agree with David WRT disconnecting the FV making it leaner -- Current through the FV decreases the pressure in the FD lower chamber......
    When I get time, I will have to hook my wideband display up and do that test (unplug the FV).
    Dave M vin 03572
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  10. #20
    Administrator Ron's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    When I get time, I will have to hook my wideband display up and do that test (unplug the FV).
    Cool! It would be interesting to know how it could go rich.
    My understanding from the manual is that the ECU normally holds the duty cycle at 70% (open 70% of the time) and, as in a manual example, raising it to 80% enriches the mixture. If you disconnect the FV, it would be open 0% (always closed). If the valve is closed, no fuel/pressure would be bled from the lower chamber. The resulting higher pressure would reduce the normal deflection away from the injector ports in the upper chamber, causing less flow through the injectors. The O2 sensor would see it go lean but it wouldn't be able to communicate with the disconnected FV.
    ...The temp would be virtually the same, so the WUR wouldn't change the Control Pressure and the thermistor wouldn't signal the ECU to change the Idle Speed Regulator. WOT and acceleration enrichment systems are out -- I can't think of anything else able to change it...

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