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Thread: How does the Auto decelerat?

  1. #51
    Senior Member Bitsyncmaster's Avatar
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    I fixed the FD leak but now it does not like to hold a good dwell. I'm going to replace the O2 sensor to see if that helps. It also takes a lot of cranking to start the engine cold but that may be the mixture setting. It does idle good. I checked the AFR and it is also not holding at idle. High RPM seems OK.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  2. #52
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    Quote Originally Posted by Bitsyncmaster View Post
    I fixed the FD leak but now it does not like to hold a good dwell. I'm going to replace the O2 sensor to see if that helps. It also takes a lot of cranking to start the engine cold but that may be the mixture setting. It does idle good. I checked the AFR and it is also not holding at idle. High RPM seems OK.
    The motor (when cold) starts on the CSV so the idle has nothing to do with starting at that point. Verify the CSV is squirting when cold. An O2 sensor going bad tends to have a smaller swing in the dwell readings. One way to rejuvenate an O2 sensor is to heat it up with a torch and try to burn out the contaminants. Can't hurt to replace it though.
    David Teitelbaum

  3. #53
    Senior Member Bitsyncmaster's Avatar
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    I did a flow test of the reassembled FD and all six jars filled the same amount. Just wanted to check it again while waiting for my new O2 sensor to arrive (think tomorrow).
    Dave M vin 03572
    http://dm-eng.weebly.com/

  4. #54
    Senior Member Bitsyncmaster's Avatar
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    I can't win. The new O2 sensor works for about 5 min then it open circuits. Seems to work fine looking at it on my o-scope and then suddenly goes dead.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  5. #55
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    A few possibilities;
    Running to rich
    Wrong sensor/defective sensor
    Bad electrical connection (could be the ground)
    Sensor cools off too much.
    David Teitelbaum

  6. #56
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by David T View Post
    A few possibilities;
    Running to rich
    Wrong sensor/defective sensor
    Bad electrical connection (could be the ground)
    Sensor cools off too much.
    Well it's defiantly a bad sensor. It was new but who knows if someone used it and returned it. But my guess is a manufacture defect. That could have got through there test because it works for about 5 min and then the output goes to almost 0 volts instantly. It's not open circuit but it must have contamination that "shorts" the output.

    Anyway, I've given up on my software update for my idle ECU. I could get it working good all the time in the garage but road testing after the engine warms up it will stall coming to a stop. I went back to the original software and that works great. I only started the update because users with an auto and stage II had problems. I may try again but I'm burned out with that software.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  7. #57
    Senior Member Bitsyncmaster's Avatar
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    Afr

    For my final test after replacing the O2 (again) and setting the dwell, I ran a cold start this morning. Had my fuel pressure gauge connected to measure control pressure and my tailpipe wideband (I don't run a CAT).

    Cold start, CP =28 PSI, AFR =11.9
    30 seconds, CP=35 PSI, AFR = 12.2
    60 seconds, CP = 44 PSI, AFR = 13.1
    90 seconds, CP = 50 PSI, AFR = 14.2

    CP stays at 50 PSI

    120 seconds, AFR = 14.3
    180 seconds, AFR = 14.5

    Then O2 goes closed loop at 3 minuets and AFR holds around 15.8. That is at 850 RPM idle. I bumped the idle up to 1000 RPM and AFR went down to 15.4. I thought I read setting dwell should be done at 1100 RPM but I could not find that document. It does look like the unheated narrow band sensor does need higher RPM to accurately hold 14.7 AFR. If anyone can find that document of using 1100 RPM please let me know. What I can do is add 1100 RPM to my idle ECU.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  8. #58
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    Quote Originally Posted by Bitsyncmaster View Post
    For my final test after replacing the O2 (again) and setting the dwell, I ran a cold start this morning. Had my fuel pressure gauge connected to measure control pressure and my tailpipe wideband (I don't run a CAT).

    Cold start, CP =28 PSI, AFR =11.9
    30 seconds, CP=35 PSI, AFR = 12.2
    60 seconds, CP = 44 PSI, AFR = 13.1
    90 seconds, CP = 50 PSI, AFR = 14.2

    CP stays at 50 PSI

    120 seconds, AFR = 14.3
    180 seconds, AFR = 14.5

    Then O2 goes closed loop at 3 minuets and AFR holds around 15.8. That is at 850 RPM idle. I bumped the idle up to 1000 RPM and AFR went down to 15.4. I thought I read setting dwell should be done at 1100 RPM but I could not find that document. It does look like the unheated narrow band sensor does need higher RPM to accurately hold 14.7 AFR. If anyone can find that document of using 1100 RPM please let me know. What I can do is add 1100 RPM to my idle ECU.
    What you are looking for is D:04:01 and :02 in the Workshop Manual. The speed is 950 RPM. It is the factory procedure to set the mixture screw by measuring CO and HC.
    David Teitelbaum

  9. #59
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by David T View Post
    What you are looking for is D:04:01 and :02 in the Workshop Manual. The speed is 950 RPM. It is the factory procedure to set the mixture screw by measuring CO and HC.
    Thanks. Guess I don't need to change the ECU software because it already can select 950 RPM.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  10. #60
    Senior Member Bitsyncmaster's Avatar
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    Well wrapping this up (for now), running the old idle ECU software works so good on my car I'm aborting the software update. I would need to test with an auto stage 2 car to determine what to change.

    Also the stock narrow band O2 sensor runs lean at idle speed (about 15.8 AFR) but with throttle above 2000 RPM (cruising speed) I get 14.8 AFR (no load, car still). Not sure how that lean idle would affect emissions testing but it would be interesting if a heated O2 sensor was tested.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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