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Thread: High Idle When Warm

  1. #11
    Senior Member NckT's Avatar
    Join Date:  Jun 2011

    Location:  Yorkshire UK

    Posts:    197

    My VIN:    No. 4068

    They were originally used to balance air flow and idle speed on non electronic idle motor systems. (The engines with the auxiliary air valve where the electing idle speed control valve should be).

    I personally use this to an advantage to get rid of the idle and off idle hunting. I described this in Post No.19 in:

    http://dmctalk.org/showthread.php?15...umpiness/page2

    As far as the air admittance deceleration springs, you could either replace the throttle assembly in its entirety, replace the throttle plate discs, or solder then shut.

    Good luck

    NickT
    Last edited by NckT; 10-20-2017 at 06:57 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....

  2. #12
    Senior Member
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    Location:  West Sayville, N.Y.

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    Quote Originally Posted by Jonathan View Post
    Snug? Is snug a better choice of words? I hadn't meant to imply them being torqued, but rather not loose. If they were valves, I'd have said closed as opposed to open.

    Out of curiosity, when would you want to adjust these screws anyway? Page D:01:13 of the Workshop manual (fuel and emissions section) states that this single air adjusting screw and the two air balancing screws are not to be used on the DeLorean since we have an electronic idle speed control system. If they get adjusted, isn't that only trying to correct a problem elsewhere (per the design that is)?
    Generally from the factory the CO (Shear style heads) were left a few turns open and the shorter slotted screw was closed which blocked off both CO bank screws. This allowed you to raise the idle for CO adjustments without fiddling with the CO screws. It also allows you to temporarely raise the idle for some other yet to be solved fault causing low idle/stalling conditions. It is usefull to leave the screws set to the factory positions for the above reasons.
    Rob

  3. #13
    Senior Member JRNY13's Avatar
    Join Date:  Aug 2012

    Location:  Massachusetts

    Posts:    150

    My VIN:    5757

    Ok, so today I drove the car again and it was idling pretty much fine cold and warm. When I noticed the high idle before, it was after a period of the car sitting for about 3 weeks. Now I'm thinking it may have been throttle cable related. Could the throttle linkages have loosened up after driving it several times this week?

  4. #14
    Senior Member Rich's Avatar
    Join Date:  May 2011

    Location:  San Francisco Bay Area, Calif.

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    My VIN:    0934

    Club(s):   (NCDMC) (DCUK)

    Quote Originally Posted by JRNY13 View Post
    Ok, so today I drove the car again and it was idling pretty much fine cold and warm. When I noticed the high idle before, it was after a period of the car sitting for about 3 weeks. Now I'm thinking it may have been throttle cable related. Could the throttle linkages have loosened up after driving it several times this week?
    Yes, that's possible.

    Next time you get a high idle see if you can push the throttle linkage closed with a dowel or a screwdriver at the arm closest to the throttle body just to verify the problem is a mechanical one. See if you get normal idle right away.

    From there the root causes vary. The cable is one of them.
    March '81, 5-speed, black interior

  5. #15
    Junior Member
    Join Date:  Jan 2018

    Posts:    4

    Sorry to revive an old thread.

    Iím tracing a high idle issue when 11477 warms up.
    My checks have led me to suspect the decel springs.

    I removed the W-pipe and this is what I saw (zoom in to see the left spring.... it seems out of position....)


    She has a brand new idle motor, a refurbished idle ecu, no vacuum leaks....
    The idle microswitch only reduces idle when the car is cold.......

    The curb idle screw is all the way out and not touching anything (previous owner).
    Iíve disconnected the throttle arm and the butterflies canít be closed any more to bring the idle down.

    Iím hoping the decel springs are the culprit as Iíve been chasing this issue for a months!!!

    Thanks guys
    Tris

  6. #16
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

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    My VIN:    03572

    That left spring looks funny. Mine both looked like some coils were close and other coils looked wide. You can probably feel with your finger if that left spring has the same pressure as the right spring.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  7. #17
    Junior Member
    Join Date:  Jan 2018

    Posts:    4

    Quote Originally Posted by Bitsyncmaster View Post
    That left spring looks funny. Mine both looked like some coils were close and other coils looked wide. You can probably feel with your finger if that left spring has the same pressure as the right spring.
    I saw some of the picks with back spring coils. Mine look ok, except the left one looks not be seated correctly.
    Could this potentially cause a high idle when the car warms?

    She idles nicely when cold. As she warms, the idle gradually increases.

    Iíve also been suspecting the thermistor......

    Tris
    Vin #11477
    Ď82 Gray 5 speed

  8. #18
    Delorean Guru
    Join Date:  May 2011

    Location:  Northern NJ

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    The left spring just looks like it is not seated properly. They look nice and shiny and they do not appear to be distorted from heat. If they snap the valve plates shut and hold some tension on them when closed, they are probably OK.
    David Teitelbaum

  9. #19
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

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    My VIN:    03572

    Quote Originally Posted by TristanC View Post
    I saw some of the picks with back spring coils. Mine look ok, except the left one looks not be seated correctly.
    Could this potentially cause a high idle when the car warms?

    She idles nicely when cold. As she warms, the idle gradually increases.

    Iíve also been suspecting the thermistor......

    Tris
    I fought the same problem many years. Cold was fine but when hot the idle climbed to about 1000 RPM with the curb idle screw all the way out. My deceleration springs were the cause of that problem. No one has the correct springs I've seen. Even if you get them I would think you need to calibrate them. The spring caps screw to adjust the spring pressure.
    Attached Images
    Dave M vin 03572
    http://dm-eng.weebly.com/

  10. #20
    Administrator Ron's Avatar
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    +1 on the left spring...but it looks like the valves are shut to me.

    How high is the RPM when warmed up?
    I'm wondering if the ISM could be sitting in a cold position and not moving since it idles nicely cold, then gradually increases (assuming it never goes down at all). I'd try letting it cool all night (below 15C/69F). Then start it up, let it run a few seconds to settle, disconnect the ISM and note the RPM. [Should be in cold position.] Then let it warm until the fans cycle once, note the RPM and reconnect the ISM. If the RPM then falls but not to idle, I'd guess the ISM system was ok and look elsewhere. If the RPM does not change, I'd suspect the ISM system has a problem.
    You could record the thermistor's resistance at the beginning and end of the test to see if it is changing/compare the values to those found posted here somewhere...(Disconnect Idle Speed Control Unit, harness side pins 9 & 11, BS/BY).

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