Solving Idle/surging Issues With Iac Mod

Discussion in '1994 - 1995 Specific Tech' started by varunner, Jun 18, 2014.


  1. varunner

    varunner New Member

    Joined:
    Jun 16, 2014
    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    1
    Hi All,

    I'm a new member here. I have a 95 mustang GT auto trans. Engine is stock except for headers, CAI. I recently added a different cam, very mild specs. So as others have experienced, the idle is rough, somewhat expected, but the problems is that it dies when put into gear, and also pretty bad surging in idle and in gear. I checked thoroughly for vacuum leaks. So after searching for help by moding the IAC, I put an extra gasket in place and cut through both of them creating an open space between the 2 air holes giving it a constant by-pass. At the same time I re-set the idle using the procedure found on this site. This greatly improved the idle, and eliminated the surging, and so far it doesn't die when put into gear. So my question is how do I fine tune this modification ? Just by ear ? O2 sensor reading ? I don't have a WB O2 now, but plan to. Thanks in advance. Great site btw.

    Brian
    #1
  2. revhead347

    revhead347 I have face herpes.

    Joined:
    Jun 14, 2004
    Messages:
    6,469
    Likes Received:
    258
    Trophy Points:
    124
    They actually make a little plate that goes under the IAC that you can adjust the bypass with two little allen screws. It's not very expensive. It's something that we used to use in the long long ago. Now everyone runs a tune anyway, and you can adjust it through the tune, so there really isn't a need. Do you happen to know what your vacuum is at idle?

    Kurt
    #2
  3. varunner

    varunner New Member

    Joined:
    Jun 16, 2014
    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    1
    Vacuum at idle is around 15" I have a tweecer. Do you know if the bypass can be regulated with a tweecer ?


    #3
  4. revhead347

    revhead347 I have face herpes.

    Joined:
    Jun 14, 2004
    Messages:
    6,469
    Likes Received:
    258
    Trophy Points:
    124
    15" of vacuum is plenty. You should be able to adjust the IAC to hold a good idle with a tweecer without any bypass modification. Keep in mind that the IAC is a common failure item. An old IAC can cause problems controlling idle.

    Kurt
    #4
  5. varunner

    varunner New Member

    Joined:
    Jun 16, 2014
    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    1
    That's good to hear. Would you have any experience with a tweecer doing this ? what parameters, setting ? thanks
    Brian
    #5
  6. revhead347

    revhead347 I have face herpes.

    Joined:
    Jun 14, 2004
    Messages:
    6,469
    Likes Received:
    258
    Trophy Points:
    124
    Unfortunately I have no experience with the tweecer. We used to have quite a few people on here that messed with the tweecer setup, but most people have swapped to the Moates Quarterhorse now. I've never messed with either.

    Kurt
    #6
  7. varunner

    varunner New Member

    Joined:
    Jun 16, 2014
    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    1
    I found about 6 different settings for ISC in the tweecer. A couple of them deal with idle speeds, so I'll have to try a couple of things. Not sure if I'll undo what I did to the gasket or not. Sure would be nice if I could find some good tuning info. Just a little info here and there. thanks

    Brian
    #7
  8. toyman

    toyman SN Certified Technician

    Joined:
    Jul 20, 2007
    Messages:
    1,804
    Likes Received:
    34
    Trophy Points:
    49
  9. varunner

    varunner New Member

    Joined:
    Jun 16, 2014
    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    1
    Nope, But I sure will. thanks
    #9
  10. varunner

    varunner New Member

    Joined:
    Jun 16, 2014
    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    1
    Seems all is good now. In addition to the gasket mod I did, I found a conflict within tweecer. There was an idle setting associated with the ISC that had to be within 100 rpm with the Idle in neutral and Idle in gear setting. Thanks for the help.

    Brian
    #10

Share This Page