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Thread: Cracking noise and missing. Tach also jumping. Help!

  1. #1
    Customized Member 81dmc's Avatar
    Join Date:  Feb 2013

    Location:  Magnolia, TX

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    Cracking noise and missing. Tach also jumping. Help!

    Could this be a bad distributer cap?

    Car wants to stall in gear (600 rpm), and I'm 40 miles from home now...

    Rodolfo
    VR6 Swap in Progress...
    Delorean.eu Roof Box, Double Din, Custom Instrument Cluster w/Cruise, QA1 Suspension.

  2. #2
    Senior Member Bitsyncmaster's Avatar
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    Location:  Leonardtown, MD

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    My VIN:    03572

    Do you have a stock ignition? I ask because I had a GM unit that needed a capacitor and it made a skip like that.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  3. #3
    Customized Member 81dmc's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    Do you have a stock ignition? I ask because I had a GM unit that needed a capacitor and it made a skip like that.
    I have the gm unit with the capacitor you sent me...

    With further testing it actually seems like your idle ecu is malfunctioning. AC will no longer bump idle and the clicking is actually coming from the vacuum solenoid.

    Idle is randomly jumping now too, but if I unplug the ecu, it just stays low.
    Rodolfo
    VR6 Swap in Progress...
    Delorean.eu Roof Box, Double Din, Custom Instrument Cluster w/Cruise, QA1 Suspension.

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

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    Quote Originally Posted by 81dmc View Post
    I have the gm unit with the capacitor you sent me...

    With further testing it actually seems like your idle ecu is malfunctioning. AC will no longer bump idle and the clicking is actually coming from the vacuum solenoid.

    Idle is randomly jumping now too, but if I unplug the ecu, it just stays low.
    At least you can bump your idle up with the curb idle screw to get home. PM me your address and I will send you another ECU and you can return the old ECU in the same box. Let me know if you have the 9 or 11 pin ECU.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  5. #5
    Administrator Ron's Avatar
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    Weird noise!
    In the video, were you pinching off the line that goes to the distributor (it should be the furthest port from the electrical plug on the vacuum solenoid, iirc), or was it the feed line to the vacuum solenoid? The reason I ask is
    I don't think pinching either one should have changed anything since the vacuum solenoid should be shut and not supplying vacuum to the distributor at idle.
    Are you sure it is the vacuum solenoid causing the noise...ie not something else causing it to flutter...or maybe the vacuum advance diaphragm has a hole in it...or the plate loose?

    Just throwing out ideas...

  6. #6
    Customized Member 81dmc's Avatar
    Join Date:  Feb 2013

    Location:  Magnolia, TX

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    Went ahead and installed Dave's new ecu. Unfortunately, it did not fix my issue. I was at a loss.

    However tonight, while I was fixing a bad led tail light, I had my ignition set to run for about 30 minutes. In that time, I could hear the damn clicking noise! Turns out the clicking is coming from the idle speed motor, but also every time the idle motor clicks, the vacuum solenoid clicks open. I confirmed this by unplugging and repplugging the solenoid while the issue was occurring.

    So what could be the issue? Is it a sticking idle speed motor that causes Dave's idle ecu to reset?

    Here's a quick video while the anomaly occurred. Also, after a key cycle, it didn't happen again....

    Rodolfo
    VR6 Swap in Progress...
    Delorean.eu Roof Box, Double Din, Custom Instrument Cluster w/Cruise, QA1 Suspension.

  7. #7
    Administrator Ron's Avatar
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    The noise going away when you pinch off the vacuum line is the main clue, imho.
    You didn't answer- Was the vacuum line you pinched in the first vid going from the vacuum solenoid to the distributor?

  8. #8
    Senior Member Bitsyncmaster's Avatar
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    We just had another owner have a problem with advance coming on at idle. It would come and go. After 3 idle ECUs and a new vacuum solenoid it still was intermittent. It has to be an intermittent connection to the solenoid. What he did was just leave the advance hose off (plugged the free hose). I will have to re-due his wiring when I get a chance but he found no problem running without the advance.

    Note:
    You get advance when the solenoid has no power as long as your engine has warmed up.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  9. #9
    Administrator Ron's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    Note:
    You get advance when the solenoid has no power as long as your engine has warmed up.
    Yes! So I'm guessing, since pinching off the vacuum advance line makes the noise stop, the vacuum switch is fluttering because it is defective or being powered on and off, OR, the the vacuum switch is always passing vacuum and the distributor has a problem (eg advance diaphragm torn and fluttering, or ??).
    ...or am I missing/forgetting something?

  10. #10
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

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    Quote Originally Posted by Ron View Post
    Yes! So I'm guessing, since pinching off the vacuum advance line makes the noise stop, the vacuum switch is fluttering because it is defective or being powered on and off, OR, the the vacuum switch is always passing vacuum and the distributor has a problem (eg advance diaphragm torn and fluttering, or ??).
    ...or am I missing/forgetting something?
    I've never pulled an advance solenoid apart. All I know is when not powered, the advance is on and the vent is closed. When powered the advance is off and vent is open. I did find one solenoid that only provided half the vacuum so I guess that vent was always open on that one.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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