Results 1 to 4 of 4

Thread: Light Throttle Miss/Stumbling

  1. #1
    Join Date
    Jul 2018
    Posts
    1

    Default Light Throttle Miss/Stumbling

    Hi Guys,
    I am wondering if someone can help me with my issue with my engine constantly surging and missing under light throttle cruise. It runs great from about 25% throttle and on, idles well, and misses at all rpms with light throttle. I have been on the phone with MSD for an hour today and they were helpful but we never got to the bottom of it.
    The engine is a SBC 383 with a Weiand Single plane intake
    Cam flat tappet 236/236 @0.50" 0.500" lift
    Return style fuel system with in tank pump. Pressure set at 41 psi. I have tried it up and down without any luck.
    Setting for the fuel pump is non PWM return style.
    I have the MSD timing control with the 6AL and also an MSD capacitive filter.
    Timing settings are Idle: 14 @800rpm
    All in: 34 @ 2500rpm
    Manifold vacuum type is ported
    Vacuum advance is 2 degrees. I have tried moving this up as high 10 and down to 0 with no change in the problem.
    AFR is set to 14 at cruise and idle. 12 at WOT
    IAC is in the single digits at idle. We did some adjustments to this while on the phone with MSD.
    Cam Shaft setting is on Mild. I had it on performance and moved it to mild and it made my idle a lot better. It was reset after moving to mild.
    Below is a link to a video I took of the hand held while the car was running rough.
    https://vimeo.com/279146275
    Another Video of the throttle body while the car is idling. It seems like the fuel is just dripping into the intake. I was assured by MSD that this was normal but it doesn't seem to be well atomized to me.
    https://vimeo.com/279082022

    Thanks in advance
    Johnathan
    Last edited by JohnathanMacAdam; 07-09-2018 at 03:48 PM.

  2. #2

    Default

    A better video would be of the dash setting the gauge has, with the bar graphs. It's really hard to see transient conditions with the numerical values for AFR.

    I do see a lean spike but I can't tell or really hear when you step into the throttle at all. Have you tried playing with pump shot / power valve?

  3. #3
    Join Date
    Jun 2017
    Posts
    1

    Default

    Quote Originally Posted by elucidus View Post
    A better video would be of the dash setting the gauge has, with the bar graphs. It's really hard to see transient conditions with the numerical values for AFR.

    I do see a lean spike but I can't tell or really hear when you step into the throttle at all. Have you tried playing with pump shot / power valve?
    I had a similar issue on my engine. 233 degree cam and eventually fixed the surge by going to the street cam setting. Wierd but it works and the car drives perfectly. Good luck

  4. #4
    Join Date
    Jun 2013
    Posts
    6

    Default

    Hi Johnathan.

    I hade the same problems back in 2013.
    Try more timing.
    Al in at 1800 and vacum advace 15.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •