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Where is my knock sensor (CA truck)

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by btolenti, Dec 5, 2003.

  1. btolenti

    btolenti 1/2 ton status

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    I cannot find the knock sensor for my ESC. My 86 is a cali emissions L-code 350. I want to replace the knock sensor, because I have been told it can cause engine miss problems at high speed (highway driving, my truck has an intermittent miss).

    I have checked both sides of the block, down by the oil pan, and both sensor locations have plugs in them, not sensors. Would the knock sensor be mounted anywhere else? Do I even have a knock sensor?

    FYI, I have the 7 pin ignition module....
     
  2. Kyle89K5

    Kyle89K5 1/2 ton status

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    The only place that I've seen it would be on the pass. side right beside the starter. I can't imagine where else it could be, but I'll pull my books and see. It may be that it was pulled and plugged and that really IS your problem...
     
  3. btolenti

    btolenti 1/2 ton status

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    according to a wiring diagram I got off this site, California trucks did not have ESC....I am just wondering "why?"
     
  4. btolenti

    btolenti 1/2 ton status

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  5. dyeager535

    dyeager535 1 ton status Premium Member

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    That link is taking forever to load, but the way the manuals are written, what that PROBABLY means, is that the next page in that manual covers the CA only ESC system, or, since the ESC system was integral with the CCC system that came on some CA trucks, there would be no seperate wiring diagram for that application. ESC was a "standalone" on non-CCC/EFI trucks, so a seperate wiring diagram in those applications makes sense. With EFI/CCC, I believe ESC is located in the ignition or driveability sections of the wiring manuals.
     
  6. reeser

    reeser 1/2 ton status

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    right beside the dipstick!
     
  7. btolenti

    btolenti 1/2 ton status

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    anyone in California have a 86 blazer they could check to see if the knock sensor is on their truck?????
     
  8. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    On carbed vehicles I have seen them in the rear of the heads. It screws into one of the threaded holes in the head on the back side.
     
  9. btolenti

    btolenti 1/2 ton status

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    I have three sensors toward the front of my intake manifold.
    Two on the water neck and one directly in the intake manifold. One of the ones on the water neck is what looks like a vacuum switch, the other has a single wire coming from it. The one mounted on the intake has a yellow and black wire going to it...

    http://ftw.truckmoxie.com/showownerpic.asp?u=3627&n=350112&pos=1&album=7210

    I also have one high on the drivers side head between the 2 and 4 spark plugs....

    Could one of these be the knock sensor?????

    I am stumped!
     
  10. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Driver side head is 1 3 5 7 and that sensor is for the water temp gauge.
     
  11. btolenti

    btolenti 1/2 ton status

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    ah! I always get mixed up with Chevys and Fords.... The Ford #1 cylinder is on the passenger front side...
     
  12. btolenti

    btolenti 1/2 ton status

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    I have looked everywhere and cannot find a friggin knock sensor... Could it be because I have an L code 350 and not an M code 350?????

    I go to the Kragen and Napa sites and they have no listing for a knock sensor on a 86 K-5, L or M code! (350 anyways)

    THey do have a listing for the 305 though! Did only the 305's have the knock sensor?
     
  13. btolenti

    btolenti 1/2 ton status

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    I am wondering if the knock sensor equipped motors are the ones with the 5 pin ignition module...

    I have the 7 pin module in my HEI distributor. I think that the MAP might be controlling the timing in my application, since I have one mounted on the firewall, and have no knock sensor... But I am just thinking out loud. /forums/images/graemlins/1zhelp.gif
     
  14. btolenti

    btolenti 1/2 ton status

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    TTT! I really need some input on this? Does anyone know the difference between the 5 and 7 pin modules...
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

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    What can I say. The setup you have is MESSED UP. /forums/images/graemlins/smile.gif

    Just looked in my parts manual. It appears your truck should NOT have a knock sensor.

    Can't figure it out, but you have an ECM, a CCC carb (TPS and mix control both) MAP sensor, all the coolant temp sensors, etc., ALL indicative of the CCC system, but it doesn't appear the L code 350 had a knock sensor. It shows on the H code 305, so I doubt it's a mistake in this manual.

    Apparently you have a "Switch, ESC mdl A/trns override (K w/350L, AT,& calif)" which seems to indicate the knock sensor just wasn't used in your setup.

    First I've ever heard of it, but hey, there are LOTS of variations on these trucks.
     
  16. R72K5

    R72K5 Banned

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    also some EST used a MAP sensor and some didnt, and some also had vacuum advance and others didnt- all with 7 pin plug HEI
     
  17. btolenti

    btolenti 1/2 ton status

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    So could the MAP cause a "miss" during highway cruising? Or should I replace the ignition module first???
     

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