A9P moderate built N/A 5.0, A/F problems on engine decel

Discussion in 'Fox 5.0 Mustang Tech' started by Dominatorstang, Oct 28, 2009.

  1. MyCombo:

    A9P w/TweecerRT
    5.0, .030 over
    E-303 cam
    24LB injectors
    76mm C&L yellow tube
    75mm TB
    GT-40 intake
    AOD, 3000stall

    Changes Made to Stock Tune:
    CID, Injector slopes, MAF Transfer, TB idle airflow, Injector Timing, Neutral and Drive idle air, load scaling, idle rpm, spark tables, injector battery voltage offset,WOT spark, WOT fuel.

    The Problem:
    It runs great and I see no real issues to speak of there. The only problem I have is when starting the car, the engine immediately hits ~1300rpm and goes to drop to idle but just falls all the way down or comes back up surging and slowly stabilizing. What i see from the data log is the IAC stays around ~45% but the PW drops to 2ms as the rpms fly up starting, as the rpms drop the PW climbs and has been as high as 12ms when trying to pull back up from under 500rpm.

    My idle is about 4ms at 750rpm. I can raise my injector low slope and the problem gets better, I have had it too 100 and the car will start rite up reving to about 900rpm solid and slowly drops to idle but HEGO's are way lean with this setting. Not that I want to run it this way but just looking for the cause.

    This makes me guess that it starts up to rich or something causes the PW to go down to 2ms when still pulling 30 some kg/hr.

    Here are some links to datalogs and the tune file.

    Mustang Base.binTune

    Startup Surge.csvEngine Start and surge then die

    Driving Datalog.csvDriving Datalog

    And ideas or similar build tunes that work would be great help.
    Thank You
  2. I have tried tweeking eveything I can think of but have had no results that lead me the correct direction.

    I have a feeling the problem is in part or full due to the E-303 cam valve overlap ( I have had this problem with this cam on tune with another vehical) I feel it may caus faulse readings at the O2's at idle. The only way I know to correct this is to make a constant open loops system tuned from a Wide band or change the cam, but that is not what i want for a daily driver. Is anyone else running the E-303/Crane 2040 cam or something similar that can point me in the correct direction?

    I have also put the factory mass air flow meter on with the OEM transfer map. The car started perfect but The computer starts writing KAMs at idle to richen it up and then it starts the same with the surge.
  3. this may sound like a dumb answer but, I have an A9P 5 speed with the f303 cam. I kind of had an issue like that. I took the IAC apart and cleaned it real good. Still has a slight surge at start up but it dosent die or stall out at redlights anymore.
  4. what system are you using to change your tune?