running without a knock sensor???

Discussion in '79-95 Toyota Truck Tech' started by ray299, Feb 2, 2007.

  1. ray299

    ray299

    Messages:
    35
    running without a knock sensor?
    I cant get my knock sensor to give a reading to the ECU. Short of running another cable from the knock sensor to the ECU.... I want to disconnect the sensor.

    That being said... the knock sensor retards the timing when there is a short or open circuit... I read 5 degrees somewhere... can anyone varify this for me???
    What I'm thinking is disconnecting the sensor and advancing the timing to compensate....

    Whatchya think?
  2. ray299

    ray299

    Messages:
    35
    arrrggggg!!!

    So I put the toyota all back together (I swapped the harness incase I had a short in the line from the Knock sensor) Well, now the thing wont start... I turn the key and it sputters and then stalls like its got no fuel pressure.... Almost sounds as if the timing is off... Anyone?
  3. Bear80

    Bear80

    Messages:
    2,951
    So how do you know its not the knock sensor its self that is bad? Droping it, or a hit with a wrench is enough to screw it. Yes it retards the timming as it senses a 'knock but not constantly. There is no need to "compensate" for its absence, you will just hear the 'knock or ping with certain applications of throttle with lower grades of gas.

    HOWEVER, without a knock sensor input signal, the computer will run in OPEN LOOP. I don't remember if it looks for a ground and then open with a knock but you can probably rig something up to bypass it and fool the computer. Sounds like the air vane connector is off but I'm sure you would've seen that. If the timing was off it wouldn't even start. You may check the vacum lines to the fuel pressure regulator since they are in the area of the harness.
    Last edited: Feb 4, 2007
  4. ray299

    ray299

    Messages:
    35
    Vane connector? I could have sworn I connected all vacuum lines but I'm open to suggestions... I swapped out the knock sensor with another used one... maybe I should just spring fo rht enew one.... (its like $200!!!) and go from there...
  5. Bear80

    Bear80

    Messages:
    2,951
    the afm, its the connector on top of the air filter box.
  6. ray299

    ray299

    Messages:
    35
    Got it runnin.. that hollow box thing wasnt connected to the air intake.. still get the code...
    What would happen if I just drove it like that?
  7. Bear80

    Bear80

    Messages:
    2,951
    Well if you get a code and the check engine light is on, the computer will be running in open loop. Meaning it won't do any dynamic adjustments as you drive, and if I'm not mistaken, it will use a default fuel curve. Meaning it never "sees" the throttle open more than idle and you will notice a lack of power. Try getting another used sensor before you pony for a new one. However if it is throwing a code the sensor is bad but they can also go bad and retard the timming when it's not needed without throwing a code. The ecu is the only thing left but I highly doubt that.
  8. ray299

    ray299

    Messages:
    35
    update

    Ok.. the truck is together. It runs. It pulsates no matter what you do (the motor) one minute... then all of a sudden it will go away and run fine for a brief period... then pulsate again.
    I still get teh code 52...
  9. Bear80

    Bear80

    Messages:
    2,951
    What exactly do you mean by pulsate? and I assume code 52 is the knock sensor.
  10. ray299

    ray299

    Messages:
    35
    When it's idling it'll keep cutting out like it wants to stall but only for realy brief cuts. Time in between cuts would be 1/4 of a second to 2 seconds. If teh throddle is cracked just a tiny bit it'll pulsate realy fast. If I push the throddle plate closed the time intrevals between the cuts or pulses becomes greater....
  11. ray299

    ray299

    Messages:
    35
    I think I found the problem with the pulsation...
    It was "cutting" out... the coil wire was loose... still have the code 52 though....

  12. ray299

    ray299

    Messages:
    35
    Ok... I took out the knock sensor. Remember, I swapped this sensor with another from another truck- then got a code... Even though the sensor was known good, it had a different part number (now I look). If I put in the wrong part from the start adn chased all these problems around I'm going to kick myself... and I heard from a Toyota tech, that if the motor surges cold, it could be the idle is up too high or the cooling system hasn't burped yet... I'll let you guys know what I come up with when I put it all together... I'm torquing the manifold now...
  13. ray299

    ray299

    Messages:
    35
    no go.... changed the knock sensor and still get a code 52 (knock sensor) wtf??????????????????????????????????????????????????
    I've changed the computer, the harness, the pig tail, the knock sensor... what else is there?????????????????????????????????
  14. ray299

    ray299

    Messages:
    35
    I'm oging to run my own coax line from the KS to the ECU... I htink maybe the shield on the coax in the harness may be lettign EMI through. It might be cracked but the thing is, if it's cracked it could still test good on continuity... but let EMI interfere with the signal form the KS...
  15. 2ndGenToyotaFan

    2ndGenToyotaFan Ice-Bound Moderator

    Messages:
    8,887
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    It's complicated....
    You are clearing the codes by pulling the EFI fuse or disconnecting the bat right? (just making sure... :)) I think you may be on the right track.... since all the other tracks have been dead ends...... Good luck!
  16. ray299

    ray299

    Messages:
    35
    Ya, everytime I take the motor apart I pull off the battery cable...
    I am now thinking about pulling the knock sensr out of the harness, providing there ar eno sufficient visual defects, wrapping it in electrical tape and putting it in its own plastic protector... That will eliminate ouside interference... problem solved? :frown:
  17. ray299

    ray299

    Messages:
    35
    Ok, I spliced in a new wire for the KS... I still gett he code... all that leaves me is to put in a NEW KS... That'll have to wait for a bit since it is $200...
    I'll let fill yall in when I do it...
  18. 2ndGenToyotaFan

    2ndGenToyotaFan Ice-Bound Moderator

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    It's complicated....
    Thanks for the update Ray, sorry it's being such a pain in the :censor:

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