low idle issue. 2002 silverado 1500 5.3 v8.

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by 1mattk, Feb 19, 2013.

  1. 1mattk

    1mattk New Member

    whenever i start my truck (2002 silverado 1500 5.3 v8, 168,xxx miles) the tach will shoot up to 1,000 then gradually fall (over about 1 minute) to 450-500 and stay there and be very rough because it wants to shut off. although it neither shut off, nor has it given me trouble starting (even on exceptionally cold mornings). i have gone through 2 bottles of crc throttle body and air intake cleaner.
    i cleaned the throttle boddy really good, and after 2/3 of the first bottle i stopped put it all back together properly, and let it idle. it stayed at about 750 (which i believe is where its supposed to be???) and was perfectly smooth. then i let it be and didnt drive the truck for 2 whole days, as i went out of town. when i got back, i took it out for a drive. i really laid on it and really took off, but a big plume of smoke came out and something felt weird. i pulled into a parking lot, and what do you know, my idle was back down to about 500 even. the next day i used the rest of that bottle on the throttle body, and most of another one (i found a lot more dirt an debris i must of missed the first time), yet, my idle is staying at 500.
    any info or advice you can give would be much appreciated. thanks in advance.
  2. trentkoger

    trentkoger New Member

    Go to the parts store and get a can of Chemtool then take out your mass air flow sensor and blow off the little wire sensors in there let it air dry. Try that if it doesnt remedy it think about replacing your o2 sensors.
  3. j cat

    j cat Epic Member 5+ Years 1000 Posts

    the idle is controlled by the IAC which is in the throttle body unscrew the IAC and using a tooth brush and throttle body cleaner clean this part . do not force part to move as this will break the plastic gear teeth. inside is a motor and this valve moves to adjust the idle by changing the air into the intake to maintain 600RPM. do not use cans of cleaner this is not good. easy on the amounts used. also use a hair dryer to evap all the fluids before starting.

    the other items to check is the ECT and if corroded or does not correctly change resistance with temp replace it. measure the fuel pressures as this along with the fuel pressure regulator could be bad. If you have the PCV replace it and make sure those crankcase vent hoses are good not cracked or poor fitting.
  4. 1mattk

    1mattk New Member

    thanks you guys. il try it.
    Last edited: Feb 20, 2013

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