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Thread: High idle speed and no more surging after intake rebuild

  1. #31
    Senior Member Bitsyncmaster's Avatar
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    Location:  Leonardtown, MD

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    Quote Originally Posted by SS Spoiler View Post
    same problem, idle creeps up as it warms up.
    but if I turn my lights on and off it drops to normal.
    ideas?....
    Back off your curb idle. If it's all the way backed out then probably you deceleration springs could be bad. Also if you get ignition advance at idle that is another cause. You can test that by pulling the advance hose going to the distributor.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  2. #32
    Senior Member 82DMC12's Avatar
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    Quote Originally Posted by SS Spoiler View Post
    same problem, idle creeps up as it warms up.
    but if I turn my lights on and off it drops to normal.
    ideas?....
    Not sure what the lights have to do with it, but I'm OP and I had the same problem with idle slowly creeping up as it warms up. The problem was my linkage rod wasn't short enough to keep the throttle plates 100% closed. I had better luck adjusting it by loosening both lock nuts and turning the rod shorter rather than trying to turn just one end shorter. I was able to make finer adjustments that way. I'm not convinced I have it totally perfect (yet) but that did stop the idle from slowly increasing. I've been swamped with work and a 5-month old boy, plus the weather sucks this spring so far, so I haven't had as much time to tinker as I would like.
    Andy Lien

    VIN 11596 Jan 1982 build - owned since Nov. 2000!

    Photography and Backpacking is life.

    Was Fargo, ND
    Now Olathe, KS

  3. #33
    Administrator Ron's Avatar
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    Quote Originally Posted by DrWin View Post
    So I basically want to ask a related question: Anyone wants to chance a guess as to what is going on with my engine after my VOD rebuild?
    1. Engine cold, ambient temp below <15*C => Engine starts, hunts for 5 secs, goes to 600-700rpms and runs steady for 30 secs. Dwell meter steady at 22* (8-cyl scale).
    2. Engine warm (?), ambient temp < 15*C => Sudden change to 900rpms, runs steady for a few minutes. Dwell meter steady at 22* (8-cyl scale).
    3. Engine warmer (?), ambient < 15*C => Gradually changes up to 1100rpms, runs steady. Dwell meter has started to move between 23* and 17* (8-cyl scale).


    My impression is that the change from open to closed loop on the idle speed ECU and the changes in rpms weren't coincidental, that is the timing wasn't a match.
    I sounded more like the changes weren't syncronised, like it was several different things that actvated in sequence. (Makes sense?)

    Also, I just tested what happens when I hit the gas - It revs up to whatever and then drops down to 775rpm OR stays at 1100 rpms, seemingly at random. This strongly suggests that the throttlecable is sticking, right?
    For the first part- When it is <15°C, the dwell should be 50-60° = 25-30° on 8-cyl scale, steady. Your's is 3° below the minimum. Given that, 1. and 2. above makes sense. And for 3., it is dead on (swinging about 40° = 20° on 8-cyl scale. You might try adjusting it a tad (richer, iirc), which may bring the cold dwell up and make the warm dwell swing wider (10° instead of 6°, about 20° 8 cyl scale. (...maybe not ;-).

    The change at .2 could just be the WUR/CPR changing the control pressure (until it reaches 40°C = 104°F).

    For the last part- I agree that the linkage is at least playing a part when it stays at 1000 RPM.

    =========

    Looks like we are getting too many cars/issues for one thread...

  4. #34
    Mad scientist DrWin's Avatar
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    Quote Originally Posted by Ron View Post
    For the first part- When it is <15°C, the dwell should be 50-60° = 25-30° on 8-cyl scale, steady. Your's is 3° below the minimum. Given that, 1. and 2. above makes sense. And for 3., it is dead on (swinging about 40° = 20° on 8-cyl scale. You might try adjusting it a tad (richer, iirc), which may bring the cold dwell up and make the warm dwell swing wider (10° instead of 6°, about 20° 8 cyl scale. (...maybe not ;-).

    The change at .2 could just be the WUR/CPR changing the control pressure (until it reaches 40°C = 104°F).

    For the last part- I agree that the linkage is at least playing a part when it stays at 1000 RPM.

    =========

    Looks like we are getting too many cars/issues for one thread...
    Either that or we are getting enough cars for a great discussion/techsession.

    So - yeah… I looked into the throttle cable/body area and can tell that something is binding somewhere, b/c the throttle doesn’t automatically reset to nil after I release the throttle pedal and/or cable (if pulling from the engine bay).

    When I manually push it to nil, rpms drops to 700-750 ish and stays steady (if a little rough).

    This also seems to suggest that the idle creep up I was experiencing earlier is because the throttle spool doesn’t rotate far enough back to activate the idle speed microswitch, which causes opening the vacuum advance solenoid, which then goes on to supply vacuum to the distributor (advance). (Right?)

    So, I’ll look more into that to figure this out. Is there a “trick” to mounting throttle cable to the clip to the valve cover, from the de-ice recall kit? I kind of suspect that’s where the binding might be?


    Sent from my iPhone using Tapatalk Pro
    Please excuse the crudity of this DeLorean as I didn't have time to repair it yet.
    VIN 10207 - December '81, Gray Interior, 3-speed automatic, stock PRV engine.

  5. #35
    Senior Member Bitsyncmaster's Avatar
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    My VIN:    03572

    When I first bought my car, I found the throttle cable clamp on the passenger side valve cover had worn through the plastic coating and the that caused the cable inside to rust there and stick.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  6. #36
    Administrator Ron's Avatar
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    Quote Originally Posted by DrWin View Post
    Either that or we are getting enough cars for a great discussion/techsession.

    So - yeah… I looked into the throttle cable/body area and can tell that something is binding somewhere, b/c the throttle doesn’t automatically reset to nil after I release the throttle pedal and/or cable (if pulling from the engine bay).

    When I manually push it to nil, rpms drops to 700-750 ish and stays steady (if a little rough).

    This also seems to suggest that the idle creep up I was experiencing earlier is because the throttle spool doesn’t rotate far enough back to activate the idle speed microswitch, which causes opening the vacuum advance solenoid, which then goes on to supply vacuum to the distributor (advance). (Right?)

    So, I’ll look more into that to figure this out. Is there a “trick” to mounting throttle cable to the clip to the valve cover, from the de-ice recall kit? I kind of suspect that’s where the binding might be?


    Sent from my iPhone using Tapatalk Pro
    Mine was binding like Dave's when I got the car.
    But years later, it was the rod joints got too sloppy. Seems I had to adjust it a tiny bit longer so it would push the butterfly/lever shut, instead of shorter as Andy mentioned???

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