stalls at stop light

Discussion in '2011+ Mustang GT 5.0L Tech' started by gary2014, Dec 10, 2018.

  1. gary2014

    gary2014 Junior Member

    I have a 2014 GT with a stage 2 Roush supercharger and automatic transmission. Car has been running great with no problems. Last week I was at a stop light and my car stalls out. It has been running fine since I got the JLT big cold air intake ( for a roush supercharger) and tune was installed in Sept of this year
    What I have noticed was at the Idle it goes to 500 RPM then stalls. Does anyone know what the idle speed should be set to and what would make the engine stall
  2. stkjock

    stkjock ---- Madmin ---- Staff Member Administrator Super Moderator S197 Team Member

    idle usually is in the 700-800 range

    have you checked all the connections for the vacuum lines and joints for the air intake?
  3. gary2014

    gary2014 Junior Member

    thanks no I haven't will do that when I can clean the snow off the car(snowed last night) here in Virginia
  4. WJBertrand

    WJBertrand forum member

    Try the idle re-learn procedure. Consists of a cold start, leave it idle until fully warm then turn on and off the AC for a period (I forget the time). Perhaps someone has posted the exact procedure here. This seemed to cure my occasional low speed stalls.
  5. Macman45

    Macman45 Resident Geriatric

    Vehicle speed reporting okay? I had a flaky VSS and it would flip when load was taken off coming to a light, low idle and eventually stall. New VSS fixed it
  6. ddd4114

    ddd4114 forum member

    I've had stalling issues like this, and I've found that cleaning the throttle body fixes it. I track the crap out of my car and suck in oil through the breather tube, so I think it eventually accumulates around the throttle blade and makes it difficult for the motor to control it. In your case, I suppose it's possible that something similar is happening because you'll have more blow-by with a supercharger. It only costs a little brake cleaner and a clean rag, so it's worth trying.
  7. gary2014

    gary2014 Junior Member

    thanks to everybody that replied. I tried the Idle re-learn procedure .Seamed to sill have a erratic idle. I re-loaded the tune. It loaded slow(like it was the first time) and then took it out for a drive, didn't stall will take it out this afternoon again .
    thanks again for all the replies
  8. Marble

    Marble forum member

    Has the weather changed significantly since September? It can have an effect on your tune. If you have an unusually warm day, drive it and see if it acts the same.
  9. gary2014

    gary2014 Junior Member

    the weather is crazy last week ,snow then very cold then today in the 50's will uncover car and take it for a ride and see ……..
  10. gary2014

    gary2014 Junior Member

    took car out yesterday, and Friday of last week down loaded tune again
    everything ok now, didn't stall at light and idle is ok now. can't figure out why it lost its tune
    thank u everybody for your advice
  11. gary2014

    gary2014 Junior Member

    car started stalling again the last week of DEC. went to the mustang GURU in fredericksbug,VA and he said it was the dyno tune that I had put in when the JLT cold air was put on .Went back to the previous dyno tuner I used and that's Exactly what the problem was. He showed me the dyno specs when the JLT was put on then his . The old specs was all over the place leaned out really bad. He re -dyno it and no a problem ever since.
  12. eighty6gt

    eighty6gt forum member

    I wonder if Doug Studdard is still alive!!?
  13. Juice

    Juice forum member

    When I first got mine running, it would run fine for some time(roughly 2 tanks of fuel), then my idle would start surging as adaptive trims were "learning". No CEL on. That could be an explanation of why it would seem the car " lost" the tune. A few minor tweaks took care of my idle.
    Sky Render likes this.
  14. 406guy

    406guy Junior Member

    So it was the tune? Glad you figured it out.

    I was going to wild guess this and say fuel filter. It's easy to miss, as newer cars don't have them. I perfer to replace mine every 40k.