1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Low Speed Knocking

Discussion in '80-Series Tech' started by TLCgrappler, May 20, 2003.

  1. TLCgrappler

    TLCgrappler

    Messages:
    135
    Likes Received:
    0
    Joined:
    Mar 31, 2003
    I have noticed in my 96 LC that it knocks just a bit (maybe for about 1/4 second or so??) as it starts out from a standing start, of it I accelerate at just the right pace from a low speed of say under 10 mph. &nbsp:Does anyone think this is just a case of buying gas that is too low in octane, or do I need to replace the knock sensors or oxygen sensor or what?? Anyone else seen this? If you accelerate hard enough, its not noticeable because the engine moves quickly through the "knock region", but if you want to , you can cause it to knock longer by controlling the accelerator at the right level.
     
  2. Beowulf

    Beowulf

    Messages:
    12,526
    Likes Received:
    30
    Joined:
    Mar 27, 2003
    Location:
    Somewhere in the foothills...
    TLCgrappler,

    You will need to give us a better description of the knock and see if you can detect where it is coming from. If the truck is in park and you slowly increase the engine speed, does it knock? Only when in gear? Are you sure it is an engine noise?

    More info please.
    -B-
     
  3. BMT

    BMT

    Messages:
    325
    Likes Received:
    0
    Joined:
    Apr 1, 2003
    TLC...does it happen more now that it is warming up? Are you using 87 octane? &nbsp:Does it sound more like pre-detonation in the top end (more of a clatter) than an actual lower end knock? Mine does it and seems to clear up with the good gas.
     
  4. DRTDuck

    DRTDuck

    Messages:
    624
    Likes Received:
    9
    Joined:
    Mar 28, 2003
    Location:
    Boulder, CO
    My 96 does it as well, taking off or in park. I would call it a ping, not a knock. When I have run fuel injector cleaner, it does not do it for that tank full and maybe the next, but then comes back. I have presumed the only way to fix is to buy higher octane, but have bit the bullet as I run a tankful a week.

    TLC-is it more of an engine ping, than a knock?
     
  5. TLCgrappler

    TLCgrappler

    Messages:
    135
    Likes Received:
    0
    Joined:
    Mar 31, 2003
    After making the post, naturally, I paid a little more attention to it today.

    Actually it "knocks" more when you just lift off the accelerator slightly with the car under load...especiallly when just starting out. Only knocks when in gear, as far as I know, although I will have to rev it up a little in neutral and see if I can duplicate it. I doubt it will do it without the load.

    As to the sounds, yes, it is more like clatter or rattling (to me, thats what engine "knock" is, although meybe there's another kind I havent heard of.

    I'll try to pay attention to the gasoline and maybe give it a drink of the high octane to see if the behavior is the same. The knocking is not particularly objectionable, just make me wonder whether something needs to be cleaned, adjusted or replaced to protect anything else. There are about 90,000 miles on it.
     
  6. chiz45

    chiz45

    Messages:
    118
    Likes Received:
    1
    Joined:
    Mar 27, 2003
    worst case scenario: I have a 96 with 105k. when i first test drove it, I heard that noise as well, a pinging type noise, that increased in frequency when i stepped on the gas. I had assumed bad gas, but I had my mechanic look at it (family friend, trustworthy) and he said it was "piston slap." I told the guy that if he fixed it, and I'd buy it.

    $5k later, it runs great, and i have 1 year, unlimited mile warranty on the motor. kinda weary about it, but seems to be holding up fine.