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Thread: Engine Hunts at Start and Then Rough Idle When Warm

  1. #61
    Senior Member NckT's Avatar
    Join Date:  Jun 2011

    Location:  Yorkshire UK

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    What reading do you get on the dwell on a warm engine now?
    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. #62
    Senior Member NckT's Avatar
    Join Date:  Jun 2011

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    You could look into what I put in post No.23 (#23) in:

    http://dmctalk.org/showthread.php?15...umpiness/page3

    Good luck
    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. #63
    Senior Member
    Join Date:  May 2011

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    Quote Originally Posted by NckT View Post
    What reading do you get on the dwell on a warm engine now?

    THe dwell is between 35-45.
    Shannon

  4. #64
    Delorean Guru
    Join Date:  May 2011

    Location:  Northern NJ

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    When the motor first starts, cold, it starts on the cold start valve. It is not exactly metered and is overly rich. Kind of like a choke on a carbureated car. It only squirts while cranking so it stops shooting in fuel quickly but it takes a moment for all of that fuel to be vaporized and consumed. Once consumed the motor has to "get used to" the leaner mixture so it slows down, overshoots, the idle motor overcompensates, the idle shoots up and the idle motor has to again compensate. The pulses dampen out but it takes a few cycles. The idle ECU does not communicate with the Ignition ECU or the Lambda ECU so they all act simultaneously sometimes against each other. Each ECU operates independently but are connected because they all control the same motor but each has it's own function so some functions overlap and some don't. The quality of the idle is very dependent on all of the cylinders working exactly equally. Especially till the motor warms up and the Lambda ECU can get into "Closed Loop".
    Bottom line, some hunting when cold is to be considered normal and you do not try to "fix" it.
    David Teitelbaum

  5. #65
    Senior Member NckT's Avatar
    Join Date:  Jun 2011

    Location:  Yorkshire UK

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    My VIN:    No. 4068

    Quote Originally Posted by NckT View Post
    You could look into what I put in post No.23 (#23) in:

    http://dmctalk.org/showthread.php?15...umpiness/page3

    Good luck
    Video evidence of non hunting when cold is in post No.30

    http://dmctalk.org/showthread.php?15...umpiness/page3
    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....

  6. #66
    Senior Member
    Join Date:  May 2011

    Location:  Houston

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    Quote Originally Posted by NckT View Post
    Video evidence of non hunting when cold is in post No.30

    http://dmctalk.org/showthread.php?15...umpiness/page3
    Are you absolutely sure you're not making a trip to Houston Texas any time soon? We have nice hot weather, great BBQ, great beer and NASA is not too far away plus Delorean Motor company is in the area. I'm sure we can round up a few cars for you to tinker with.
    Shannon

  7. #67
    Senior Member NckT's Avatar
    Join Date:  Jun 2011

    Location:  Yorkshire UK

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    My VIN:    No. 4068

    I would love to come over to visit, when I get some time/ funds. I'm definitely sold on Beer and BBQ
    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....

  8. #68
    Senior Member
    Join Date:  May 2011

    Location:  Houston

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    I have dwell meter and multimeter. What setting does one use to check the RPM of the engine and where are the probes placed in the engine?
    Shannon

  9. #69
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

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    My VIN:    03572

    Most RPM meters use the ignition coil (negative side). There are some optical RPM meters but you usually need to add a foil reflector on the pulley.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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