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Knock sensor problems on '94 850 1994

posted by  someone claiming to be Don in Denver on  Sat May 3 06:55 CST 2003 [RELATED]

Check engine light came on with codes indicating front knock sensor problem
& oxygen sensor problems. Replaced oxygens sensor. Independent Volvo mechanic
said '94 had problems with knock sensor readings. He suggested I burn premium
gas instead of regular. Car seems to run a little better(not that it was bad
before)with premium but too soon to tell if this will work. Anyone else with
similar problems? Apparently this is some sort of ECU problem that is very
difficult to fix.
Thanks for any input.








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    Knock sensor problems on '94 850 1994

    posted by  jfizz on  Sat May 3 12:16 CST 2003
    Author: [PROFILE] [EVERY POST] [THREADS] [BEST POSTS] RSS Feed     [IGNORE ALL POSTS]
    last visit: Fri Aug 4 14:21 CST 2000
    [RELATED]

    There is a service kit available from Volvo for the knock sensors. It comes with 2 new sensors and a wiring harness modification. That should solve the knock sensor problem. I can't remember the part number but any Volvo dealer should be able to find it for you. I hope this helps. I'll be here if you need more info.


    Jimmy








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      Knock sensor problems on '94 850 1994

      posted by  someone claiming to be Don in Denver on  Sun May 4 13:45 CST 2003 [RELATED]

      Your suggestion sounds logical--but, then the other responders sound reasonable
      also, so I'm confused. Any idea how much this kit costs and is this something
      that can be done by a non-mechanic like me? Thanks for your help.
      Don in Denver.








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        Knock sensor problems on '94 850 1994

        posted by  someone claiming to be Frank on  Sun May 4 15:40 CST 2003 [RELATED]

        There's an old paper TSB on replacing both individual sensors with one pair wired togther with its own new wiring harness ("new and improved") but that was Volvos original idea way back in '94. They originally thought that the problem was bad connections at the knock sensors. I've done it to a few cars and in each case, the cars all came back with the exact same codes. The new knock sensors with improved connections didn't solve the problem. In each case, a replacement ECU (new or preferably used now) solved the problem. I now don't even try replacing the original '94 type knock sensors anymore as I know it'll just come back.
        I've never seen where bad cap, rotor, wires caused that code to appear.








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          Knock sensor problems on '94 850 1994

          posted by  jon alias jon on  Mon May 5 11:37 CST 2003
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          I guess in my case that's what fixed it. The problem appeared right after spark plug replacement and disappeared after replacing wires, rotor and distributor cap.
          The solution was suggested by a Volvo tech when I discussed the knock sensor codes with him. He told me that the first thing he does when knock sensor code shows up is to test ignition system components. Since I was due for spark plug replacement I just added the rest and it got fixed.
          And I can find it quite understandable that a problem with ignition system would trigger knock sensor code.
          Good luck.








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    Knock sensor problems on '94 850 1994

    posted by  someone claiming to be Frank on  Sat May 3 10:49 CST 2003 [RELATED]

    Solved by another ECU, not knock or O2 sensors nor switching fuels. Get a used ECU (about $250) and that'll cure it. I've seen this many times now with '94 turbo 850s (only '94 too).







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