Backfire and hesitation around 2500 RPM

Discussion in '2005+ Mustang GT 4.6L Tech' started by JeremyM, Jun 10, 2019.

  1. JeremyM

    JeremyM Junior Member

    Hoping someone may have something. Just swapped the engine in my '07 GT Auto. Idles great, fires right up, however I am getting hesitation around 2500RPM through 1st,2nd and sometimes 3rd. Once it breaks passed, it screams. From a stop to WOT it seems ok, just during normal acceleration.

    Validated TPS, MAF, Injectors, Coils, and installed brand new plugs and fuel filter. Any thoughts?
  2. eighty6gt

    eighty6gt forum member

    BAMA tune!?!
  3. JeremyM

    JeremyM Junior Member

    no tune unfortunately
  4. JeremyH

    JeremyH 3V Fuel Guru S197 Team Member

    Charge motion valves dirty/sticking?
  5. 08MustangDude

    08MustangDude forum member

    Sounds like it. They are programmed to open all the way at WOT, so when
    he steps on it, they flick open. When gradual, they open gradually, may be
    getting stuck.
  6. JeremyM

    JeremyM Junior Member

    Thanks for the suggestion. I'll pull the air intake manifold tonight and check everything out.
  7. JeremyM

    JeremyM Junior Member

    No dice on the charge motion valves. Pulled it all apart, cleaned the carbon build up with a wire brush and carb cleaner, reassembled and same issue. It seems to open and close cleanly. It does appear to be occurring at a lower RPM 1250-1500, but still backfires and hesitation. What's the odds that the actuator itself is bad? I can see it responding but not sure it's accurately doing so.

    Also, may be an oversight on my part, but I swear it was sprung closed when I took it off. After cleaning and reassembly it was sprung open. May be nothing more than lack of attention to detail, but what is the normal position?