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Thread: Another high idle thread - how-to on butterfly plate springs?

  1. #41
    Administrator Ron's Avatar
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    Quote Originally Posted by jawn101 View Post
    Didn’t your mother ever teach you not to pipette by mouth? Was that just me? Scientist parents, lol. Seems reasonable enough, I could give that a shot.
    LOL!
    Yeah, but note I said, "you" and "could"!

    Quote Originally Posted by jawn101 View Post
    Just a question - I’ve never done a smoke test but is this something that would make leaks obvious? I don’t even know how, though I assume it’s a quick google away.
    Smoke might work. But technically, you need to reproduce the same condition as when the suspected problem occurs and sucking is the opposite of blowing. [Don't go there -- It took a lot of self control for me not too... LOL]

  2. #42
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    Quote Originally Posted by FABombjoy View Post
    Oil rated or fuel rated hose will cure the problem. Parts stores will sell PCV rated hose, but you could use oil cooler, trans cooler, or fuel hose too. It just gets more expensive and less flexible if you use fuel/oil hose vs emissions hose.

    https://www.instructables.com/id/Why...-Oil-and-Fuel/
    Thanks for that. So it isn't all of the vacuum hose kit hoses that can't be silicone? Just the one(s) directly connected to the oil filler? Could we make a list of which ones shouldn't be silicone (by DMC part number)?


    Sept. 81, auto, black interior

  3. #43
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    A smoke test is where, with the motor off, you pressurize the induction system with smoke. Any tiny leak and you will see wisps of smoke coming out, large leaks and you get a cloud. A smoke test is not a complete end-to-end test of every hose. Any valves in the system can block the smoke. You would have to test each valve and branch of vacuum lines if you suspect leaks past where there are valves. A smoke test can't tell you if valves are not working correctly or if vacuum hoses are not connected correctly. The way I do it I remove the air cleaner box and block off the intake. I connect my smoke to the cold start valve and watch for leaks. The big ones you see quickly and are very obvious, the smaller ones take a bit longer and you have to hunt for them. Vacuum leaks are cumulative, ie, they add up. A bunch of tiny leaks can equal one big leak. Every leak potentially leans the mixture and reduces the control power of the idle system. An induction leak close to an intake valve can lean out a cylinder to the point it can detonate and burn a piston while all the other cylinders are running fine. You should be able to hear the vacuum solenoid on the ignition advance click when you hit idle. If you don't, you have to figure out why you don't. Could be a bad connection, the plug fell off the solenoid, the switch isn't adjusted right, whatever. Very common when working in that tight area in front of the motor, you knock the plug off accidentally and don't realize it. It is also VERY important you have the right hose connected to the right port on that valve. They CANNOT be reversed.
    David Teitelbaum

  4. #44
    My friends think I'm nuts jawn101's Avatar
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    Hey all, I hope everyone had a great holiday break! I was away for a few days, but am back and thinking about this issue again.

    Over the weekend I went and got new o-rings for my oil filler and also enough fuel hose to replace the line between the cap and CSV tube. I still had all the old hose clamps, so it should be very solid. Also, those new O-rings made all the difference - the old ones were very heat damaged and compressed, were making zero content with the filler neck, and were so inflexible I had to cut them off. Now the cap is very snug.

    I was playing around a bit with the idle and noticed the behavior in the video below. Basically, when I started the car up, it idled normally (cold). Then I started pressing around on the top of the idle air motor, and noticed that if I put pressure on the electrical connector, the idle changes dramatically. Like, I can rev the engine by doing so. The video speaks volumes on this, it's only 10 seconds long. Just be aware that at the end when the camera is trained on the tach, the only thing I'm doing is putting pressure on the idle speed motor electrical connection - nothing else with the throttle.

    https://www.youtube.com/watch?v=JEZbVVOiPfc

    I'm guessing this could be related to my issue?
    Jon
    1981 DMC-12 #02100. July 1981. 5-speed, black, grooved w/flap.
    restoration log, March 2011 to present
    full and detailed photo restoration log

  5. #45
    '82 T3 FABombjoy's Avatar
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    It could be electrical but seems to correlate with pressure which would be atypical. I suspect that pushing on the idle motor is shifting something downstream around.

    I'd check & push on the hoses connected to the idle valve / cold start tube and see if any of those have an affect.
    Luke S :: 10270 :: 82 Grey 5-Speed :: Single Watercooled T3 .60/.48 :: Borla Exhaust :: MSD Ignition :: MS3X Fully SFI Odd-fire EFI :: DevilsOwn Methanol Injection

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  6. #46
    Administrator Ron's Avatar
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    You might try watching the valve while pressing and releasing the plug to see if that changes its position...
    Or comparing the pressed and released RPM with the unplugged RPM.

  7. #47
    My friends think I'm nuts jawn101's Avatar
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    Quote Originally Posted by FABombjoy View Post
    It could be electrical but seems to correlate with pressure which would be atypical. I suspect that pushing on the idle motor is shifting something downstream around.

    I'd check & push on the hoses connected to the idle valve / cold start tube and see if any of those have an affect.
    It's not a bad theory given how little I show you of what I'm doing, but the idle motor is quite securely attached to the bracket/intake, so to my calibrated arm it feels like I'm only pressing on the electrical connection - though I just noticed there's a hairline crack in the epoxy/potting/whatever around the electrical connector, where it goes into the main motor housing. Maybe that's letting in additional air? I don't know what the internal structure of the motor is like, so no idea if that connector leads into an air chamber or something more isolated.

    Quote Originally Posted by Ron View Post
    You might try watching the valve while pressing and releasing the plug to see if that changes its position...
    Or comparing the pressed and released RPM with the unplugged RPM.
    Ah, interesting. So like just start the car normally and straight up unplug the idle motor?
    Jon
    1981 DMC-12 #02100. July 1981. 5-speed, black, grooved w/flap.
    restoration log, March 2011 to present
    full and detailed photo restoration log

  8. #48
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by jawn101 View Post
    It's not a bad theory given how little I show you of what I'm doing, but the idle motor is quite securely attached to the bracket/intake, so to my calibrated arm it feels like I'm only pressing on the electrical connection - though I just noticed there's a hairline crack in the epoxy/potting/whatever around the electrical connector, where it goes into the main motor housing. Maybe that's letting in additional air? I don't know what the internal structure of the motor is like, so no idea if that connector leads into an air chamber or something more isolated.
    The top electrical part of the idle motor is separated from the lower valve part. Only thing that passes through is a shaft in a bearing. The lower valve assembly has an O-ring sealing it to the outer metal cylinder. So pressing on the connector probably is making or breaking a connection. Most likely in the external connector. Pull the boot off the connector and look for a broken wire at the pins.
    Dave M vin 03572
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  9. #49
    Senior Member Rich's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    .... Most likely in the external connector. Pull the boot off the connector and look for a broken wire at the pins.
    Interesting sleuthing that potentially ties the intermittent problem to area at/near the ISM connection point.

    Maybe just unplugging/plugging the ISM connector a few times might clean up the internal pins?

    ID-ing which wire might be intermittent per Dave's suggestion - try a continuity test between each female contact in the connector and its corresponding pin-socket in the (white 9-pin) bulkhead connector. Pins 4, 8, 9 there.
    March '81, 5-speed, black interior

  10. #50
    Administrator Ron's Avatar
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    Quote Originally Posted by jawn101 View Post
    Ah, interesting. So like just start the car normally and straight up unplug the idle motor?
    No (it would probably die), I was thinking just turn the key to Run for a quick comparison/elimination...

    +1 Dave and Rich, except it's pins 5, 8, 9.

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