LS style V4 mode: Active Fuel Management

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  • The PIG Smith
    King Browless

    Moderator
    • Nov 30, 2001
    • 6538

    LS style V4 mode: Active Fuel Management

    I recently drove our company's 2008 Chevrolet Tahoe from Butler, Indiana to Pittsburgh, PA.
    This Tahoe is powered by a 5.3L V8, model LY5, that was was equipped with Active Fuel Management.
    I did not even know what Active Fuel Management was until while driving up the Interstate, the Information Center indicated V4 Mode.
    I thought it was some sorta of Variable Valve Timing, but I was wrong.
    I looked it up later and as I understand it, the computer shuts of the coil and the injector to 4 cylinders.
    Anyways, that Tahoe received economy numbers in the low 20's.
    I was greatly surprised that a truck so big and heavy could achieve better than 20 miles per gallon of gas.

    I was also shocked at how well this Tahoe drove and rode.
    That 5.3 in V8 mode has about 320 horsepower and really had the zip to get up the road! I liked the Vroom Vroom!

    OKAY...so you fellows that have performed LS swaps in a FSJ, here is my question to you:
    With an 5.3L LY5 with its 4L60E and transfercase (NP241?) can a person get the Active Fuel Management to work in a non GM vehicle?

    While doing research, I discovered that on the www.gmfullsize.com forum, folks either love it or hate it.
    Well, I can tell you that it worked well for me and I loved it.
    I had the power when I wanted and had the economy when I was just cruising.
    Seemed to be one of those examples of getting to keep my cake and eating it too!

    My hope is that this question will draw a lot of technical discussion.
    Bryan Smith
    2017 Jeep Grand Cherokee Limited
    - 75th Anniversary Edition - 1941 Trim Package - Recon Green
    1986 Jeep J20
    - Super clean rig from the AZ/CA state line
    1982 Jeep J10
    - Has become a Long Term Project.
    1981 Jeep J20
    - Commercial flat bed - Lost in a Divorce --gone
    1987 Jeep J20 Pioneer
    - Former Rick Bielec aka Ricbee plow rig. Major rust!! --gone

    IFSJA Member #1933 Joined November 30, 2001

    Originally posted by Jayrodoh
    ...but if it works, I wouldn't touch it.
    Originally posted by Lindel
    Best laid plans, yada yada yada...
  • j20owner
    258 I6
    • Jan 11, 2003
    • 355

    #2
    Well, where do I start? Can you do it, more than likely. Would I EVER use it? No.

    We've had 4 trucks in the last month come in with issues with the lifters. It's not just the coils and injectors that are shut off, it's the lifters for cylinder #1, #4, #6, and #7. The lifters are controlled by oil pressure. There's an AFM Manifold underneath the intake manifold. This is fed pressurized oil by the pump and is equipped with 4 electric solenoids. These solenoids are turned on to allow the pressurized oil to a special passage in the block the the lifter. Once around the lifter, it is fed into a port on the lifter where it enters a channel and presses two locking pins to 'unlock' the lifter. These pins are held out under spring pressure and are what actually allow the lifter to push the pushrod. We've seen these pins stick, causing the lifter to permanently unlock. This of course causes a dead miss. This happened to two of the four trucks. The other two had something break inside the lifter, causing it to be collapsed permanently, also causing a dead miss. In both cases, both heads came off, all the AFM lifters get replaced. Three of the four trucks were under 100,000 miles. The fourth had over 150,000 and the customer decided on a new engine with a warranty of a rebuild.

    Glad I could share my experience.
    Where is my axle?
    79 j20/84 GW GM Hybrid

    Comment

    • billyj7175
      304 AMC
      • Sep 10, 2001
      • 1513

      #3
      I can't add anything technical...however, if you do go with the active fuel management, stay with a quiet, stock exhaust. If not, when it activates and shuts down cylinders...it sounds really goofy. My 08' Silverado had it and a 70 series Flowmaster...had more than one person ask "what's wrong with your truck". It was that noticeable.
      83 J-10 Jeep "Oscar"
      360/727/229
      4" Rusty's w/33X12.50 BFG AT's

      I'll apologize ahead of time...my inner voice has Tourette's...

      Comment

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