Help low idle? No CEL

Discussion in 'Black Bear Performance' started by Ryanz71hoe, Nov 7, 2019.

  1. Ryanz71hoe

    Ryanz71hoe TYF Newbie

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    I’ve sent a few recordings to black bear. Each time they tell me that my throttle at idle is too low, which they are convinced is a vacuum leak. It reads at about 2% throttle at idle, when it should be around 5 to 6%. However, I’ve done numerous tests with a smoke machine and the conventional way spraying around the lines to listen for any changes. I have done quite a bit of work to the truck. Included is a spectre cold air intake. What am I missing here? Truck has 238,000. There is no check engine light on, and there’s a mile long list of stuff I have replaced just trying to get the throttle to go back up.
     
  2. Tonyrodz

    Tonyrodz Resident resident

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    What's the rpms at idle?
     
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  3. PNW VietVet

    PNW VietVet Full Access Member

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    Typically if you have a vacuum leak the idle is higher. If is a large enough leak it can idle lower but IMO it would not be smooth and low idle.
     
  4. HiHoeSilver

    HiHoeSilver Away!

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    Best way I know to confirm/deny vacuum leak is fuel trims. Do you have a scanner to see live data?
     
  5. Ryanz71hoe

    Ryanz71hoe TYF Newbie

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    Yeah I do, from black bear/efi live. What should I look for?
     
  6. swathdiver

    swathdiver Full Access Member

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    Look at your Long Term Fuel Trims at idle and while driving. If they are over 10% and up to 25% you've got a big vacuum leak somewhere. Are you using the AutoCal? You can look at O2 sensor readings and spray water or propane or MAP gas around intake gaskets and such while watching sensors to pinpoint the leak.

    I thought the idle was set by the "tune"?
     
  7. HiHoeSilver

    HiHoeSilver Away!

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    Like James said, look at the fuel trims. Short and long term. If they are elevated, watch what they do under throttle. If the short terms go negative and start to pull the long terms back towards 0, you've likely got a vacuum leak.

    For good videos to see examples check out Scanner Danner.
     
  8. BlackBearPerf

    BlackBearPerf Supporting Vendor Supporting Member

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    Hello Ryan, it looks like you and Justin had a dialogue going trying to help you diagnose your situation. There is an unanswered email that Justin sent you, he had some follow up questions, if you wanted to check, hopefully that might help out as well.
     
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