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what is this Sensor on TBI 350's

Discussion in 'The Garage' started by 89K1500Chevy, Jun 2, 2003.

  1. 89K1500Chevy

    89K1500Chevy 1/2 ton status

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    what is this Sensor on TBI 350\'s

    Anyone know what sensor is on the bottom left side of the engine block? its almost where the oil pressure sending unit is but on the opposite side of the block. /forums/images/graemlins/truck.gif /forums/images/graemlins/usaflag.gif www.zombieoffroading.8m.net
     
  2. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Re: what is this Sensor on TBI 350\'s

    If it's on the passengerside it's proably the knock sensor. Unscrew it. If no oil comes out and it's a blind hole it's the knock sensor. There will be a oil pressure swtich for the ECM as well. It's in different places different years. Some it's above the oil filter, some behind the distribor on 454's it on front of the driverside motor mount.
     
  3. Shorts

    Shorts 1/2 ton status

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    Re: what is this Sensor on TBI 350\'s

    as if gimr-reaper needs a backup, but i second the knock sensor /forums/images/graemlins/grin.gif
     
  4. HarryH3

    HarryH3 1 ton status Author

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    Re: what is this Sensor on TBI 350\'s

    [ QUOTE ]
    Unscrew it. If no oil comes out and it's a blind hole it's the knock sensor.

    [/ QUOTE ]
    Uh, if you do this, be prepared for a face full of engine coolant. All of the EFI GM engines that I've worked on have the knock sensor screwed into the block in the place of the block drain plug on the passenger side. /forums/images/graemlins/eek.gif Did this change somewhere along the way?
     
  5. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Re: what is this Sensor on TBI 350\'s

    I'll second Harry as well... its a knock sensor YES - and if you pull it from the block, I hope #1 the engine isn't hot, and #2 that you are wearing a rain coat... you are gonna get wet! /forums/images/graemlins/rotfl.gif

    -Dan
     
  6. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Re: what is this Sensor on TBI 350\'s

    [ QUOTE ]
    [ QUOTE ]
    Unscrew it. If no oil comes out and it's a blind hole it's the knock sensor.

    [/ QUOTE ]
    Uh, if you do this, be prepared for a face full of engine coolant. All of the EFI GM engines that I've worked on have the knock sensor screwed into the block in the place of the block drain plug on the passenger side. /forums/images/graemlins/eek.gif Did this change somewhere along the way?

    [/ QUOTE ]
    Ooops LOL. Every knock sensor I have ever messed with has been into a blind hole BUT I have never pulled one on a GM.
    My Goof and no wonder they go bad on GM's. /forums/images/graemlins/grin.gif
     
  7. 89K1500Chevy

    89K1500Chevy 1/2 ton status

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    Re: what is this Sensor on TBI 350\'s

    alighty then i dont think ill go pull it out. Ok so on my 89 wtf does the knock sensor do to help my truck get down the road b/c see i have not every changed it nor did i think that my truck would even have it on it and the other thing is Why does the TBI only have 1 O2 sensor???? I have replaced it but never thought about it only having 1 b/c all the new ones have like 4 to 6 mabey this is why the truck ecm says that the engine is running lean.
     
  8. HarryH3

    HarryH3 1 ton status Author

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    Re: what is this Sensor on TBI 350\'s

    It lets the computer keep the timing advanced to just short of detonation, all the time. /forums/images/graemlins/cool.gif

    TBI's were GM's first attempt at EFI on our trucks. They're pretty simple. In later years, the government got involved and the OBD II systems were created. The newer systems monitor the Air/Fuel ratio on each bank individually, both before and after the cats. /forums/images/graemlins/eek.gif The engine management systems are so sophistcated on the new stuff that they will flag a misfire on a single cylinder.

    If the ECM says that you're running lean, then you need to start tracking down the root cause of the problem.
     
  9. Bushwhacker

    Bushwhacker 1/2 ton status GMOTM Winner

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    Re: what is this Sensor on TBI 350\'s

    If you unscrew it and you dont get soaked or nothing comes out you need to stick a small screwdriver or something in that hole and break the carbon deposits loose. Seen this on two motors. The knock sensor on one had about 3/8" of carbon on the end of it, which will not let it function like it should.

    Clay
    84 K10 355TBI, D44, 14B Detroit, 8"Superlift, 36" Mickey's
    Bushwhackers Offroad Outfitters
    Indian Trail NC
     
  10. 89K1500Chevy

    89K1500Chevy 1/2 ton status

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    Re: what is this Sensor on TBI 350\'s

    Yeah but now OBDIII is about to come out and if you thought the OBDII was cool just wait it knows everything.....Time,Date,promblem,how you were driving(ie hotrodding or granny)
    Ok so i wonder if i should go ahead and get a new knock sensor dont see how it would hurt anything if i did so i might as well get as many new parts on it as possible. BTW my truck passed emissions so good i almost fell on the floor it was crazy that it ran so clean. /forums/images/graemlins/thumb.gif
     
  11. stu

    stu Registered Member

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    Re: what is this Sensor on TBI 350\'s

    The new OBD III is a Big Brother theory come true. ENFORCEMENT MECHANISMS

    Incorporate into biennial I/M program
    Read fault code to screen for vehicles that need complete testing
    Pass or short test for vehicles with no fault code
    Does not speed up repair process
    Out-of-cycle inspection
    Compile and screen data
    Mail notice to vehicle owner requiring out-of-cycle inspection within 10 days
    Require Certificate of Compliance (C of C) on next registration/resale, or
    Require C of C within 30-60 days, with citation for noncompliance
    Enforce citation via court and/or DMV penalty at next registration
    Roadside Pullover
    CHP flags down vehicles with fault codes
    Technician verifies problem by inspecting and/or testing vehicle
    Issuance of notice requiring out-of-cycle inspection
    Same enforcement (C of C /citation)
    LEGAL ISSUES

    OBD-III imposes sanctions based on "suspicionless mass surveillance" of private property
    Random, possibly frequent testing
    No advanced knowledge vehicle will be tested
    Results of testing not immediately available (unless roadside pullover follows)
    No opportunity to confront or rebut
    Possible use of system for other purposes (Police pursuit/immobilization, tracking, cite speeders)
    OBD-III raises 4th Amendment search and seizure privacy issues:
    ''The right of the people to be secure in their persons, houses, papers and effects, against unreasonable searches and seizures shall not be violated...'' (emphasis added; also see Art. I, Sec. 19 of Calif. Constitution)
    From legal perspective, it is unprecedented: previous cases have looked at surveillance of individuals

    odbIII
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: what is this Sensor on TBI 350\'s

    [ QUOTE ]
    Ok so i wonder if i should go ahead and get a new knock sensor dont see how it would hurt anything if i did so i might as well get as many new parts on it as possible.

    [/ QUOTE ]

    Replacing known good parts with ones of questionable origin (this applies to new parts too)is definitely false economy.

    I believe one test of the knock sensor is to watch the timing, while tapping on the exhaust manifold with a hammer. If timing retards, it's working.

    You can also watch knock counts with a scanner.
     
  13. 89K1500Chevy

    89K1500Chevy 1/2 ton status

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    Re: what is this Sensor on TBI 350\'s

    im going to put my truck on the scanner tomarrow b/c i dont think it was even picking up the knock sensor before. i did scroll and look at all the things on there but dont remeber seeing the knock sensor reading anything but 0(mabey a good thing) I havent ever replaced it and everything i have replaced was bad and making the engine run poorly.
     

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