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Thread: Lambda Dwell not swinging

  1. #1
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    Lambda Dwell not swinging

    Maybe someone can help here - the DeLorean runs perfectly fine, warm, cold everything, milage, but that concerns me:
    • When measuring dwell for the Lambda the needle is not swinging - see video here: https://photos.app.goo.gl/wUoPmnPb2eQxKTGg7
    • When I actuate the WOT switch the needle goes a little to the left (seen in the video)
    • When I ground the cable to the Lambda the needle very slowly goes almost to the left (not shown in the video)
    • I have replaced the Lambda probe but that did not change anything
    • I measure the dwell from the diagnostic plug orange cable and ground
    • The frequency valve buzzes, when I disconnect it, the engine RPMs react a little


    I can perfecly live with this condition as the car runs fine, but as a mechanic I always want to get to the bottom of things :-)
    Any hints here what can cause this behaviour?

    thanks..............Eugen
    '81 DeLorean, 20.000 mls, second owner, automatic gearbox

  2. #2
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    Either;
    You did not hook up the dwell meter correctly,
    Your dwell meter is not working,
    Or you don't have the meter set up right.

    Connect to a GOOD clean ground and check the connection to the Lambda wire. It sounds like the Lambda system is functioning so you should be getting better readings.
    David Teitelbaum

  3. #3
    Senior Member AugustneverEnds's Avatar
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    Perhaps it's not going into closed loop. You stated you replaced the lambda (oxygen) probe so it's probably not that. Check the lambda ECU behind the driver's seat for loose connections or poor grounds. If you are able try swapping the ECU with a known good unit.
    Nick A.

    1988 BMW 325is
    1982 DeLorean DMC-12
    1989 Jaguar XJ6

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    Administrator Ron's Avatar
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    Quote Originally Posted by eseethal View Post
    Maybe someone can help here - the DeLorean runs perfectly fine, warm, cold everything, milage, but that concerns me:
    • When measuring dwell for the Lambda the needle is not swinging - see video here: https://photos.app.goo.gl/wUoPmnPb2eQxKTGg7
    • When I actuate the WOT switch the needle goes a little to the left (seen in the video)
    • When I ground the cable to the Lambda the needle very slowly goes almost to the left (not shown in the video)
    • I have replaced the Lambda probe but that did not change anything
    • I measure the dwell from the diagnostic plug orange cable and ground
    • The frequency valve buzzes, when I disconnect it, the engine RPMs react a little


    I can perfecly live with this condition as the car runs fine, but as a mechanic I always want to get to the bottom of things :-)
    Any hints here what can cause this behaviour?

    thanks..............Eugen
    It sounds like the O2 sensor is not connected/bad (even though new).
    Did you try applying 1.5V to its lead (see WS Manual D:04:15, 5.)?

    +1 Nick.

  5. #5
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    Thanks for your help here! Sorry for the late reply - I did not get the notification messages from the forum.
    I will check the Lambda unit, but have no spare one to replace it.
    The dwell meter should work, I remember having used this before on the DeLorean. The ground also is good. It reacts to the WOT switch. When I ground the Lambda wire the needle of the dwell meter goes to the left side slowly. Next time I will try the 1,5 V battery test.

    thanks, greetings from Austria..........Eugen
    '81 DeLorean, 20.000 mls, second owner, automatic gearbox

  6. #6
    Motors about after dark Michael's Avatar
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    Make sure that O2 sensor is a Bosch and not some cheap part. I have back to back vids with brand new China junk vs. Bosch and the difference is obvious.
    http://dmctalk.org/image.php?type=sigpic&userid=90&dateline=161808992  9

  7. #7
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    Thanks, yes, it is from delorean.eu - they have the right parts. And the not-swinging was with the previous lambda sensor too.

    [QUOTE=Michael;276189]Make sure that O2 sensor is a Bosch and not some cheap part. I have back to back vids with brand new China junk vs. Bosch and the difference is obvious.[/QUOTE
    '81 DeLorean, 20.000 mls, second owner, automatic gearbox

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    Your Freq valve is buzzing....continuously or on/off?

    the meter reading tells me continuous.

    sometimes if the base mixture is too far off- lean or rich, the system cant adjust, and it stays at one value.

  9. #9
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    Thanks, the valve is continously buzzing. The mixture I measured with a CO-tester and a Wideband Lambda should be correct. The car runs fine, the fuel consumption is also o.k :-)
    '81 DeLorean, 20.000 mls, second owner, automatic gearbox

  10. #10
    Junior Member poidog's Avatar
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    Quote Originally Posted by eseethal View Post
    Thanks, yes, it is from delorean.eu - they have the right parts. And the not-swinging was with the previous lambda sensor too.
    delorean EU carries chinese junk O2/Lambda probe... the same one that DMC houston carries. I just recently put a new one in from DMC and it failed in less then 3 months, same symptoms as you, it would not swing and stick at 45 degrees open loop. I put in a new Bosch 02 prob and it is working normal now and swinging properly. Replace the O2 probe with a bosch unit and I bet money on it that it solves your problem.

    Make sure you have your meter connected properly - the orange wire connector that would go to the diagnostic plug and use the engine hook or AC bracket as a grounding point.
    Last edited by poidog; 05-31-2023 at 02:32 PM.

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