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Engine Knocking, don't know what to do

Discussion in 'GM Powertrain' started by silveradokid, Jan 3, 2010.

  1. silveradokid

    silveradokid New Member

    I have a 99 silverado 4.8L and it has brand new knock sensors and brand new oxygen sensors of the passenger side. After i replaced them ses light came on and said the O2 sensors weren't working, then the light went back off after a day. And i can here knocking in the engine, thought replacing the sensors would work since there was knocking before i replaced them and one of them was bad. Any thoughts on why its still knocking?
  2. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    Engine Knocking, dont know what to do

    I see you have a Hypertech programmer. What tune are you runing, 87 or 93 octane?
  3. azdrtdog

    azdrtdog Epic Member 5+ Years 100 Posts

    Whoa is it KNOCKING or pinging from detonation becuase knock sensors dont fix rod bearings
  4. silveradokid

    silveradokid New Member

    I'm really not sure, i think its pinging, i just here this noise from the engine when I'm doing 40, and i gas it at about 2000rpms i can here it but its not very loud, used to be worse before i replaced the two sensors. And i run 89 all the time. I filled up about 20 miles ago with 91 premium. I was told i could have some water in the gas tank, and to put some rubbing alcohol in it?
  5. azdrtdog

    azdrtdog Epic Member 5+ Years 100 Posts

    A predetonation will sound like a thump or clack and it will stumble along with various cylinders throughout the entire firing order. it is controlled by timing and exhuast gas mixing from egr. unless you have heavy carbon build up that is causing hot spots or the egr passages are starting to plug up the pcm should be able to tune it out but that engines kinda new for that stuff
  6. silveradokid

    silveradokid New Member

    Its hard to describe, i mean its a not very loud and just sounds like something isn't working properly. I can only hear it at low rmp's, and im pretty sure it is pinging but i would think the computer could have stopped that by now. I went offroading and i noticed the noise that day, i'd say i did a good amount of bouncing around, is it possible something is out of place or a loose connection?
  7. azdrtdog

    azdrtdog Epic Member 5+ Years 100 Posts

    Pretty sure its internal noise? not a motor mount that might be torqing just high enough to studder or a single exhuast leak that only comes on with load
  8. silveradokid

    silveradokid New Member

    It almost sounds like squeaking. Before i replaced the knock sensors it was a lot louder and way worse. Now its just not very loud. Ill try to take a video or something and let you here the sound for yourself because you know more than i do. I'm pretty sure its pinging but I'm not positive.
  9. silveradokid

    silveradokid New Member

    Oh and if it helps, going uphill it gets worse, you can really here it going up hill. But in order to here it i have to have the windows rolled up.
  10. azdrtdog

    azdrtdog Epic Member 5+ Years 100 Posts

    Ya that sounds like a ping make sure the sensor is tight and dont use teflon tape or silicone it will act as a buffer and not let the knock sensor catch the slight detonations

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