Rough Idle and Spark Advance Question

Rough Idle and Spark Advance Question

This is a discussion on Rough Idle and Spark Advance Question within the F150 Ecoboost Problems forums, part of the F150 Ecoboost Forum category; I’ve got a 2015 3.5 eco with 54k miles on it. Truck went to the dealer few months back for a rough idle and the ...

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Thread: Rough Idle and Spark Advance Question

  1. #1
    Rookie EastokEB's Avatar

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    Rough Idle and Spark Advance Question

    I’ve got a 2015 3.5 eco with 54k miles on it. Truck went to the dealer few months back for a rough idle and the dealer said it needed entire passenger bank of injectors. Since then it has had all new plugs gapped to .03 and cleaned the Map sensors on the intake. The injectors definitely improved it but I am still having a rough idle especially coming down from high idle. I know these trucks are known to have an occasional shake at idle but this seems more than what I have felt in other 3.5s. It’s been back to the dealer twice now and they can’t find anything wrong. I run FORScan on my 6.0 diesel so I decided to hook it up and start monitoring some things. My idle at warm bounces between 600-700 constantly without ever really settling down. But what really bothers me is my spark advance. When the truck is bouncing between idle points my spark advance goes from about 3 all the way to 15 and won’t find a steady advance point to stay. I’m also monitoring my MAP which is all over the place just like my idle and my advance. I still get 22mpg on the highway so it doesn’t seem to be affecting the mileage. Does anyone have what Ford considers acceptable MAP readings? Also I have read that it’s hard to say what the proper spark advance should be but is it normal for it to be so unsteady? I have tried premium and regular along with no ethanol all of which run the same.

  2. #2
    Eco-Beast noodles's Avatar

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    Start the truck and let it idle for 20 mins without touching anything, so it can complete the idle relearn procedure.
    Some of these trucks do have a "rough" idle with really retarded timing advance.
    snakebitten and Mikedick77 like this.
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  3. #3
    Rookie EastokEB's Avatar

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    Tried the idle reset and got a little better idle now but still pretty rough. I know these trucks aren’t perfectly smooth but this just seems more than what’s normal. After the idle relearn my spark advance jumped between 7-12 instead of 0-12. Does anyone know if this kind of variation is normal? I would expect to see it stay somewhat constant with slight variations but not a constant 5 degree variation.

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  5. #4
    Ecoboost Master Envious's Avatar

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    What do your LT and ST fuel trims look like?

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  6. #5
    Rookie EastokEB's Avatar

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    Measured fuel trims below:

    LT1: 2.34
    LT2: -2.34

    ST1: varies between -3.12 and -.78
    ST2: varies between 0 and 2.34

    Looking at the data I pulled from a 2 minute idle at operating temperature it seems the fuel trim changes lead the timing advance changes so I assume the fuel trim is what’s causing the spark advance flutter.

  7. #6
    Ecoboost Pro Boostking's Avatar
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    Any way you can post the log?

    Generally, when being read as a trim from Lambda, STFT and LTFT's should hopefully be around 1.0 (stoich) which is no correction. Usually you will have wiggle room of 3-5% which will settle on the LTFT trim and the STFT will be right on or about 1.0 constantly (after learning).

    Your values seem to be in different units or I'm not sure what they are. If you had terrible fuel trims, I would expect to see something like .86, or 1.25. THe -3.12 and +2.34 are throwing me off. Maybe they are already converted to percent? But then what is the -.78...

    Do you have any way to datalog and post the logs?

    Spark will jump to counteract unstable idle. Add spark to bring idle up, dump spark to drop it. Map will flutter with this because the throttle will need to open and close slightly to control the air (IAC) which changes vacuum. You could have a sticky IAC, or a bad MAP (unlikely).

    Log the following if you can

    IAC or Idle Air Integrator
    Throttle Angle Actual
    Spark Advance
    Spark for Idle Control
    Spark Source
    Envious likes this.
    2013 Tuxedo Black SCrew Ecoboost FX4 w Appearance Package 5.5 box, 3.73. Mods: SCT LWTS+ custom tuned, Full-Race/BorgWarner OEM+ "GT Turbos", Tifosi Exhaust Manifolds, RTR HPFP, CP-E FMIC w/ TurboSmart SuperSonic, CP-E 3" Catted Downpipes, AFE Magnum Force Pro Dry-S Intake, Borla Touring Cat-Back, Terra G2s 305/55/20 on Method N/V 20x9, Leveled Bilstein 5100 RHA 1.5", 20" LED light bar, Hellwig Rear Sway Bar, Morimoto LED Fogs, Extang Revolution Tonneau Cover, Custom LED bed lighting, DeeZee Tailgate Assist, Tailgate Remote Power Lock Mod, MaxLiner Floor Mats, Ford OEM Underseat Cargo Box, LED Interior and Reverse Lights (Diode Dynamics), Recon LED 3rd Brake Light, NL Door Detents, .50 cal antenna, Custom Coding (ForScan)

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