96 GMC Suburban - surging while stopped (only in drive and reverse)

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by McDucken, Dec 16, 2013.

  1. McDucken

    McDucken New Member

    Hi All, I'm a new member to the forum - I bought a 96 suburban SLE 4x4 and had the engine replaced - old one was blown. new motor is a 5.7L vortec same as what was installed only high flow air intake and a throttle body riser... truck runs awesome except when stopped with my foot on the brake - it idles at about 800 - 900 and suddenly it drops about 200 rpm and surges wanting to pull away. lights dim and sometimes it stalls. this only happens when the transmission is under load (in drive or reverse gear) idles at 900 - 1000 rpm while in neutral or park and it does not surge at all. some of my research has indicated that this is a PCM issue and a reflash with new programming cures this - after the engine swap the stereo stopped working (is this related - I have no lock code should this be due to the anti-theft system) - thanks for any insight you can provide - McDucken
  2. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Normal idle is between 500 and 600 rpm.

    Does anyone know if this year had "drive by wire", or a throttle cable?
  3. Conlan Rose

    Conlan Rose Epic Member 5+ Years 1000 Posts

    A 96' oooo I know those! :lol:. The Vortec has a throttle cable. Also to fix the radio I think there is info on how to get it working again in the owners manual if it is the factory radio. I will look over mine to check. Because the battery was out a long time when it was repowered it might of locked up because of a theft lock system, but not sure if these trucks have that.

    Idle should be around 600-700 normally for these trucks or at least that where mine idles.

    Here are the 2 pages on they theft-deterent system.
    radio1.jpg radio2.jpg
    Last edited: Dec 17, 2013
  4. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Haha, I knew you were the expert (where's that thumbs up smiley).

    A mechanical adjustment should return the idle to "normal".

    On some engines, a dirty throttle body will cause the engine to surge.

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