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Why is tach bouncing?

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    Why is tach bouncing?

    Hey guys, a question.
    I just changed my plugs, cleaned my O2 sensor, cleaned my temp sensor, and adjusted my valves. Now my car runs much better.
    I have another problem, though. Now my tach is bouncing all over the place, also my MPG guage. Why is this doing this? It didn't before.

    Does anyone have any ideas?

    #2
    Could be the SI batteries, or bad wiring, among other things. I suggest chaning the SI batteries first, and if that doesn't work, maybe replace the tach unit.

    97 Cosmos M3

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      #3
      I don't know. I let the car sit for about 3 hrs and now it's fine. weird, huh?

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        #4
        Loose ground on the back of the cluster?


        Broken wire in the SI board?


        Those are my guesses.
        My mountains are better than yours.

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          #5
          okay, i'll check both of those out next weekend.

          thanks

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            #6
            mine started like that, it went crazy

            and couple days later, it died ....

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              #7
              Originally posted by grlaneriejr View Post
              I don't know. I let the car sit for about 3 hrs and now it's fine. weird, huh?
              i've been having that problem since i bought my car a year ago. i have the motrometer display and i thought that it would start to bounce to a higher rpm when it was hot cuz after it sat for a while it would be steady again. well i have been driving it everyday for the past month and no jumping and now i have the problem again today. when i rev it high it will seem to catch up and read acurate again until the rpms drop. i also had my ecometer bounce down and my mph bounce down for a few minutes one day. is this the problem you're having and did anything fix it?
              sigpic
              1987 - 325i Convertible Delphin Auto [SOLD], 325i Convertible Delphin Manual [SOLD]
              1989 - 325i Convertible Bronzit m30b35 swapped [SCRAPPED], 325i Sedan Alpine Auto[DD]
              1991 - 325i Coupe Laguna Manual [Project], 535i Sedan Alpine [SCRAPPED]

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