“Pop, pop, pop…” sound from intake manifold

Discussion in '80-Series Tech' started by Han Solo, Jan 22, 2010.

  1. Han Solo

    Han Solo

    Messages:
    7
    Location:
    NorCal
    Strange, “Pop, pop, pop…” sound from intake manifold

    94 FZJ80

    When I advance the throttle from idle I hear a, “pop, pop, pop…” sound coming from the intake manifold, I think. The noise has become progressively louder during the past week. The noise is only present during accelerations, once a desired RPM is selected the sound stops and the truck seems to continue running fine. No notice in power loss.

    Any theories or solutions for a fix would be greatly appreciated.
  2. MikePL

    MikePL

    Messages:
    775
    Location:
    Warsaw, Poland
    Wow, today while wiring my auxiliary lights I also noticed this strange popping sound. What could it be? It comes exactly from the driver's side. On the passenger side is the usual valve chatter.
  3. Ebag333

    Ebag333

    Messages:
    8,163
    Location:
    Medford, OR
    Predetonation possibly?
  4. sdbrassfield

    sdbrassfield

    Messages:
    655
    Location:
    Flatwater, NC
    Exhaust leak possibly if only on acceleration and it goes away after it gets hot. Does it go away after the truck is warm ?
  5. Han Solo

    Han Solo

    Messages:
    7
    Location:
    NorCal
    I was thinking along the same lines. As I accelerate in RPM’s the popping noise also accelerates. I don’t think I notice the sound as much when the engine is warm. It’s really noticeable at slow speeds, leaving a stop sign, etc.

    This maybe a separate issue but I looked under the truck and noticed from the catalytic converter down to the muffler the whole assembly is vibrating. The vibration noise has been apparent for sometime; perhaps a mount broke while wheeling? Maybe these two issues are part of the same problem?
  6. Pin_Head

    Pin_Head

    Messages:
    11,842
    Location:
    OC, CA
    Running lean on one or more runner? Bad injector?
  7. lacruiser

    lacruiser

    Messages:
    874
    Location:
    Los Angeles
    is the popping actually coming from inside the intake manifold? (If you remove the air filter cover you should be able to hear it more clearly.)

    Or is it just coming from the area of the intake manifold.

    If it's a true popping back through the intake manifold, in the old days that indicated either a lean condition, a spark that was not where/when it was supposed to be (like spark jumping wires and/or carbon tracking inside the dist. cap), a flat camshaft on one lobe, or a sticky (weak or broken valve spring) or partially-burned intake valve.
  8. MikePL

    MikePL

    Messages:
    775
    Location:
    Warsaw, Poland
    In my case the popping comes from the area of the intake and it is irregular. Sometimes it pops three times in a row within 2 seconds and then a 3 second pause, then a few pops and another pause etc... Strange.
  9. lacruiser

    lacruiser

    Messages:
    874
    Location:
    Los Angeles
    Maybe check the spark plug wires to see if one or more is arcing to ground.

    Look at the engine running in the dark, you can sometimes see sparks.

Share This Page