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Thread: Stuttering under acceleration when warm

  1. #41
    Member
    Join Date:  Feb 2015

    Location:  Allen, TX

    Posts:    36

    My VIN:    #4595

    Quote Originally Posted by NckT View Post
    Hello. Yes, I'm referring to those brass hex headed bolts as in the picture.

    Don't forget the metric feeler gauge (or whatever the imperial equivalent would be)

    Re the wot switch, try spreading electrical switch cleaner or wd40 at the point where the full load switch presses on it. Disconnecting it will prove if it is the wot causing it to go into a fixed dwell or not.

    Good luck with it all.

    NickT
    Thanks for clarifying. I ordered the feeler gauge last night on good old amazon prime so will have it in a couple of days!

    Good tip on cleaning the switch. I have a can of electrical cleaner that I'll run through it when I get the chance.

  2. #42
    Member
    Join Date:  Feb 2015

    Location:  Allen, TX

    Posts:    36

    My VIN:    #4595

    I've made the final adjustments to the curb idle/idle switch screws as well as the 3 brass hex screws. I didn't notice any particular difference when driving it, but it may just be that I was pretty close on those already.

    After running for a bit though, I did have that bizarre Dwell issue again. During initial warm up the dwell measures like it should and RPMs are right around 850 at idle. Dwell is solid at first then swinging between 35-45 or so. After the car has been run for a while though (10 mins or so), that dwell reading starts moving higher but still swings a little bit but has a much smaller oscillation. Every so often, it would hold steady for several seconds around the 48-50 range and if I revved the engine a bit, the dwell would begin to swing but in the range of 45-50. It would do this over and over and while hot, would never really drop below 45 or so. Idle also seemed to be increased a bit to around 1000 - 1050 or so.

    It definitely is not the WOT switch since if I press that, the dwell pegs closer to 60. Likewise, disconnecting the WOT switch doesn't affect the dwell.

    Any ideas on why the dwell would change that much as the engine warms up? Is this something to be concerned with? Let me know if you need additional data points.

    Thanks!

  3. #43
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

    Posts:    6,716

    My VIN:    03572

    Quote Originally Posted by bueller View Post
    I've made the final adjustments to the curb idle/idle switch screws as well as the 3 brass hex screws. I didn't notice any particular difference when driving it, but it may just be that I was pretty close on those already.

    After running for a bit though, I did have that bizarre Dwell issue again. During initial warm up the dwell measures like it should and RPMs are right around 850 at idle. Dwell is solid at first then swinging between 35-45 or so. After the car has been run for a while though (10 mins or so), that dwell reading starts moving higher but still swings a little bit but has a much smaller oscillation. Every so often, it would hold steady for several seconds around the 48-50 range and if I revved the engine a bit, the dwell would begin to swing but in the range of 45-50. It would do this over and over and while hot, would never really drop below 45 or so. Idle also seemed to be increased a bit to around 1000 - 1050 or so.

    It definitely is not the WOT switch since if I press that, the dwell pegs closer to 60. Likewise, disconnecting the WOT switch doesn't affect the dwell.

    Any ideas on why the dwell would change that much as the engine warms up? Is this something to be concerned with? Let me know if you need additional data points.

    Thanks!
    You set your dwell with the hot engine. What your seeing are pretty small changes. Are you reading dwell or duty cycle? I ask because WOT reads 60% duty cycle. I still think your dwell adjustment is set a little high.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  4. #44
    Member
    Join Date:  Feb 2015

    Location:  Allen, TX

    Posts:    36

    My VIN:    #4595

    Quote Originally Posted by Bitsyncmaster View Post
    You set your dwell with the hot engine. What your seeing are pretty small changes. Are you reading dwell or duty cycle? I ask because WOT reads 60% duty cycle. I still think your dwell adjustment is set a little high.
    I haven't actually adjusted Dwell at all since I've owned it so this is still the default dwell from when I bought it and the tamper proof plug is still in place. I didn't change it after getting fuel pressures adjusted since the readings were dead on while warming up and after the 02 sensor kicked in -- Just seeing this oddness when the engine's fully warmed up.

    As far as dwell vs. duty, I'm not really sure I understand the difference and I've probably been using the terms interchangeably. I'm using an Actron analog dwell meter (CP7605) set to Dwell and I've connected the green/positive to the diagnostic port per this video (https://www.youtube.com/watch?v=cpNB1eRktzM) and the negative to a ground on the engine itself. All my references throughout this string to dwell settings were with the above connections. However, as I think about it, now I'm not sure it wasn't a 50 reading vs. a 60 reading with WOT pressed -- the key takeaway for me with regards to the WOT switch was that pressing it did make a difference in the reading and disconnecting it didn't change any of the readings.

    If it would help, I can definitely take some videos of the meter readings again so that everyone can see exactly what I'm describing.

  5. #45
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

    Posts:    6,716

    My VIN:    03572

    Quote Originally Posted by bueller View Post
    I haven't actually adjusted Dwell at all since I've owned it so this is still the default dwell from when I bought it and the tamper proof plug is still in place. I didn't change it after getting fuel pressures adjusted since the readings were dead on while warming up and after the 02 sensor kicked in -- Just seeing this oddness when the engine's fully warmed up.

    As far as dwell vs. duty, I'm not really sure I understand the difference and I've probably been using the terms interchangeably. I'm using an Actron analog dwell meter (CP7605) set to Dwell and I've connected the green/positive to the diagnostic port per this video (https://www.youtube.com/watch?v=cpNB1eRktzM) and the negative to a ground on the engine itself. All my references throughout this string to dwell settings were with the above connections. However, as I think about it, now I'm not sure it wasn't a 50 reading vs. a 60 reading with WOT pressed -- the key takeaway for me with regards to the WOT switch was that pressing it did make a difference in the reading and disconnecting it didn't change any of the readings.

    If it would help, I can definitely take some videos of the meter readings again so that everyone can see exactly what I'm describing.
    Your using dwell. So book number are correct. Duty cycle numbers are 10% higher than dwell numbers.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  6. #46
    Member
    Join Date:  Feb 2015

    Location:  Allen, TX

    Posts:    36

    My VIN:    #4595

    Got some time to work through adjusting the mixture screw and now I have everything dialed in with dwell centering on 40 when the engine is fully warmed up. I took her for a spin today and can say she is easily running better than she has since I got her. No trouble accelerating anymore -- all stuttering and hesitation is gone.

    Many thanks to Dave M, NickT and others who've assisted in this thread!!

    For those needing to adjust the mixture, I was pretty gun shy given all that I'd read here but once you get everything else buttoned up properly, it's not terribly difficult. The drilling out of the tamper proof plug is the hardest and most nerve wracking part. I followed the directions on this thread (http://dmctalk.org/showthread.php?83...justment-screw) and had no issues. For those who wondered what the tamper proof plug actually looks like when it's removed, here are a couple of pictures. I tried finding similar pics so I had an idea how deep to drill, etc. and couldn't find them. Hopefully this will be helpful to others also:

    Note: The screw you see is not part of the tamper proof plug, but you probably knew that already
    IMG_20171014_113034.jpg

    You can see the steel disc in the bottom of the plug that is mentioned in the link above:
    IMG_20171014_113041.jpg

    Thanks again for everyone's help. Nick and Dave M, if you're ever in the Dallas area, please look me up as I owe you lots and lots of beer.

  7. #47
    Senior Member NckT's Avatar
    Join Date:  Jun 2011

    Location:  Yorkshire UK

    Posts:    135

    My VIN:    No. 4068

    You're welcome. I'm glad it's sorted and that the shims made the difference to the performance exhaust.

    NickT

    Ps I love beer
    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....

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