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350 Pings in the morning - normal?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Rootbeer, Nov 25, 2002.

  1. Rootbeer

    Rootbeer Registered Member

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    My 90 Blazer with a 350 has 120k miles on it, and runs great but pings for about the first 2 blocks of driving. A sticker on the door jam says I have a hypertech chip that the previous owner didn't mention so I dont know what other mods it has. Is pinging normal in the morning or should I check the timing? /forums/images/graemlins/confused.gif

    -Mike
     
  2. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Pinging is NEVER normal. It's a good way to fry a motor. Ping can be caused by a few things. Lean fuel mix (if the computer has gone closed loop) Replace the O2 sensor and that will probably cure it.
    EGR not functioning correctly. could be EGR could be control.
    Timing.
    Since it goes away once warm I would suspect the O2 sensor and really I would replace it anyway. The recomended service interval on most O2 sensors is 60k. Check the timing for sure.
    The other issue may be that chip is going closed loop before the engine and O2 is warm.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Is the thing pinging only when cold, or even when warm?

    If its cold, the 02 isn't working, so that won't be the cause.

    I'm not a big fan of the hypertechs, they've been disassembled, (and tested) and all they really do is change the timing, and not enough to make any difference. Waste of money.
     
  4. Stoopalini

    Stoopalini 1/2 ton status

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    Are you sure you are hearing pinging? You definitely should not be getting any detonation with a TBI motor. Your knock sensor should pick it up immediately and retard timing. I believe this will happen even in open loop mode.

    Are you getting any codes? If your pinging bad enough to hear it for a long enough time, your ECM should throw a code at you and kick into "limp home mode". If this happened, you would definitely know it because half of your power would be gone.

    Thomas.
     
  5. TopOff

    TopOff 1/2 ton status

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    Sounds like the chip settings for open loop are wrong. Could also be that you are running regular unleaded (87 octane). The hypertech maybe configured for Super Unleaded (91 octane). I know that's how my other car is setup. It will ping if I use regular unleaded.

    Another could be clogged or dirty fuel-injectors and/or a bad wire/sparkplug.

    BTW: You can't really change the timing on the 90. The computer changes it. If you do change the timing the computer Check Engine Light will come on.

    Good luck.
     
  6. Rootbeer

    Rootbeer Registered Member

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    When I pulled into the driveway at my house I could hear the pinging again so I popped the hood. I noticed the AC compressor clutch kept clicking on for a few secs, then off for a few. I unplugged it and it stopped turning on, the idle lowered, and what I thought was pinging stopped.
     
  7. Stoopalini

    Stoopalini 1/2 ton status

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    Were you running the defroster? If you run the defroster, the A/C compressor will engage to remove moisture.

    If your A/C compressor was kicking on, then off, then on, then off .... you might be low on freon and the safety switch in engaging. You can get an A/C guage at Autozone for a couple bucks and check the pressure.

    Thomas.
     

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