Bank 1 and 2 running lean problem.....

Discussion in 'Chevy Truck Forum' started by jrod2025, Dec 22, 2013.

  1. jrod2025

    jrod2025 New Member

    Dec 22, 2013
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    Hey guys! I have a 99 silverado 4.8 with 108k miles on it. The check engine light will go on and off frequently and i checked it and it say bank 1 and 2 running lean. ive cleaned the MAF sensor, fuel filter checked intake gaskets, changed trottle positioning sensor and hasnt seemed to help. Does anyone have any suggestions? Also when its cold out and I first start it up in the morning and it idles up and down and the lights go dim like it wants to quit. Ill back up out of my driveway and go to take off and it doesnt wanna take off then it punches the gas and I can take off. When its warm outside it doesnt seem to rev up and down as bad.
  2. chevychase

    chevychase Semi-Admin
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    Oct 15, 2010
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    truck forum .org
    Could be many things cause this...vacuum leaks at intake..throttle body/air intake gasket it sets on...air filter housing/plenum from throttle body to air filter has a leak..vacuum lines..could be a faulty maf../dirty...02 sensor getting sluggish..leak at exhaust manifold..fuel pressure down.
    Here is some links to look over will be the same for the 4.8 on diagnostics first link probably your problem a member here batty was his what happens as engine gets warmer metal expands sealing the leak some

    P0171 Chevrolet Fuel Trim System Lean Bank 1 OBDII Engine Light Trouble Code |

    Is your GM Truck with the 4.8L, 5.3L or 6.0L engine experiencing a rough idle? Or is your check engine light on, with codes PO300, PO171, PO174 and PO332? «

    Part 1 -GM MAF Sensor Test (4.8L, 5.3L, 6.0L, 8.1L).

    AGCO Automotive Repair Service - Baton Rouge, LA - Detailed Auto Topics - How to Test a GM Fuel Pump
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