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Low idle issue

Discussion in 'Engine & Drivetrain' started by Hammer02, Apr 12, 2021.

  1. Hammer02

    Hammer02 TYF Newbie

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    Kris
    2002 yukon denali 6.0
    Low idle
    So low the ac goes warm at lights or drive thru.
    Engine has never stalled out tho.
    Sits around 500
    Cleaned the throttle body today.
    New plugs and wires today as well.
    Went to clean the IAC but I have this body....
    aaz-67-3010.jpg

    First off Idk if this is even the one that is supposed to be on there or not but its what came with it.
    I say that cause I have found some questionable stuff the previous owners have done IE: replacing the front diff with a 4x4 diff that was disengaged so I eventually burned up my transfer case.

    So as you can tell it only has a throttle servo and the TPS. No IAC.
    Where is it?

    So I ask what can I do or check for the low idle issue and where is my IAC located?

    I thank you for your help!
     
  2. ks03

    ks03 Full Access Member

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    Just clean the throttle body. With electronic throttles I think carbon buildup acts like a wonky iac
     
  3. Hammer02

    Hammer02 TYF Newbie

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    Thanks for the help:)....but I did mention that I had cleaned the throttle body already.
     
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  4. ks03

    ks03 Full Access Member

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    Maybe a better way to say it is that every electronic throttle I’ve come across has not had a separate IAC valve. The idle air is controlled by the main throttle. Cleaning the throttle body on an electronic throttle typically has a more significant effect on idle quality than a cable actuated throttle
     
  5. Doubeleive

    Doubeleive Supporting Member

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    on your 2002 (drive by wire) the iac is built into the electronic plastic part on the side (throttle position sensor), it's not serviceable but can be replaced, if it were me I would just replace the whole throttle there not that much. If it was a 00 or 01 it would still have a throttle cable and the iac is separate and can be cleaned.
    if you are trying to save money, rockauto sells the throttle position sensor part alone (it has the iac built in to it)
     
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  6. fasteddy

    fasteddy Full Access Member

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    OMG no A/C at the drive thru? That's a problem in some states.

    How long have you owned the Denali?

    Low idle?
    2002 Denali 6.0 is Drive by Wire or cable? I don't know...02-03-04 are transition years
    If that picture is your TB then you are DBW.
    Is this a new problem? Like when did it start (after plugs and wires? or before)
    All the time?
    From morning start till end of day?
    At low idle is engine rough or smooth?

    No check engine light?


    Any funny noises under the hood?

    How's you battery? And alternator?
    How many amps are you pushing on the cluster at 500rpms.
    Have you hooked up a charger or booster to it and see if that changes the RPMs?

    Is it constant at 500rpms? or does it go up and down? Is it hunting?
    Have you looked at the MAF? its between the airbox and tube that goes to the throttle body
    Bad/dirty MAF could cause low idle (but would throw a code and hunt)

    Air Cleaner OK?
    Clogged air intake would constraint air but rpms would vary as it struggled to recover....Computer has target idle setting.....like 700 i think.
    Is air intake stock or other?
    Is it free of debris?

    Is it the stock cam? New cam can cause low/struggling idle without tune.

    If your TB was a problem it would most likely throw a code and go into Reduced Power Mode

    How did your old plugs look when you pulled them out?
    Clean? Oily? wet? Burned? Black? missing tips? or just gray and old.
    Are they all completely plugged in? Its hard sometimes to get to the CLICK.

    What does your latest MPG say from last personal tripometer?
    How many miles do you get on a tank of gas.....
    Do you run regular or premium?

    There could be a connection between your A/C or other belt driven devices and your idle too.
    If A/C or P/S or Alt bearings go bad it could place more load on the engine and drive the idle down.
    So any funny noises? Or the bearings in the pulleys too.....they would sound aweful...


    Denalis are cool....stock 6.0
    Shave those heads/stuff a cam in there=almost 500hp....very cool.
     
  7. fasteddy

    fasteddy Full Access Member

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    Also

    Bad fuel can jack with your idle (may not throw a code) (put in some injector cleaner, octane booster, or E85)
    I dont know if your Denali can run E85.....E98 would be better. That would clean up a fuel issue.

    Bad fuel injectors can jack with your idle (would most likely throw a code....like a p1517 lean code, maybe not)

    Transmission torque converter going bad can place more load on engine (may not throw a code)

    Cracked intake manifold or vaccum leak can jack with your idle (may throw a MAP code ...depends)

    Things to check......
     
  8. fasteddy

    fasteddy Full Access Member

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    Lastly

    How does it run from idle to 5K?
    Does it feel sick or healthy once you get out of idle?
     
  9. Ben Prokop

    Ben Prokop TYF Newbie

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    If you cleaned the TB on the vehicle I’m hoping you used actual throttlebody cleaner and suction/vacuum as opposed to just a rag on your finger (which by the way worked great On my O2 Caddy EXT) but on my current 2012 Yukon Dinali I tried the same, open the throttle manually, spritz, wipe, let dry, on fire up things were slightly better but The problem still persisted identical to what you’re talking About. So long story short it ended up being tired stretched timing chain. So oddly enough I poured matched polished heads did the cam and put headers as well as open catalytic‘s and straight pipes with an Edge programmer now I have 597 horse to the fly wheel! With a very unsteady idle! The work was only done 2 weeks ago and I broke the drivers side motor mount tonight no my way home from work!!
     
  10. Ben Prokop

    Ben Prokop TYF Newbie

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    Wow voice to text doesn’t know how to spell Yukon Denali and I definitely didn’t poured any matches into my head lol!

    I’m actually wrenching on the truck now to fix this damn mount and gloves and grease make typing impossible.,any tips? Or does everything I think I have to remove really have to come out to get the new one in clean?
     

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