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    #1

    Bad Tach Reading?

    Hello guys, I just purchased my 89 325is last week. I think the Tach on the car is not accurate due to the fact that the tach reads between 4500-5000 rpm at 75-80 mph. Also I noticed that the car will rev past the 7000rpm mark, do these cars have rev limiters? By the way the car is a one owner, 135k miles, 100% stock car. Someone told me that the car could also have a 4.10 diff, this car is supposed to have a 3.75 lsd, right?

    Also, I noticed a louder than normal valve ticking at highway speeds, is this normal or should I have them adjusted?

    Thanks in advance:up:
    Tags: None
    #2
    Lots of questions, I'll help out where I can.

    Yes they do have a rev limiter, so I am going to agree that you have a tach issue. I know that there is a something somewhere, I think the diff, that gives the signal to the ecu for the tach. Someone else will know better than me. I know that the 89 IS automatics had 4.10 LSD's in them, not so sure about the 5-speeds. There should be a metal tag bolted to the back of the diff, it takes a 17mm to get it off. Take it iff, and clean it up, it will tell you what diff the car has.

    If you can hear your valves tick at high speed 60+mph, you should get that checked out. Most of the time the tick will get louder at higher revs not with higher speed. If they get louder at high speed then you might need to look somewhere else for the issue.
    Originally posted by KingB
    Scratch my back and I buy a prostitute for you, to rub your balls. HAHA now thats some funny shit.

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      #3
      I mean you should be able to bury the needle before the fuel pump cuts you off. Because you can doesnt mean you should.

      More than likely if you can hear valves ticking, but the motor runs fine and you dont feel an extreme loss of power, you probably need a valve adjustment.

      You seem new to E30s, so just realize on these motors and the same with the next generation of M50 family motors, you're going to hear a certain amount of "clicking". If you hear it at high speeds, someone may have tried to adjust them and did so incorrectly. Just take the valve cover off and visually inspect for broken rocker arms and major discoloration. Thats a freebie.

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        #4
        That tach reading in 5th is about right for a 4 cylinder coding plug in the cluster. A PO could have swapped the cluster.

        If someone swapped in a 4.10 diff in place of the 3.73 that a manual transmission car would have, the engine would be turning right around 4000rpm at 80mph. Seems like you are seeing greater engine speed, which might best be explained by the wrond cluster coding plug.
        The car makes it possible, but the driver makes it happen.
        Jim Levie, Huntsville, AL

        Comment

          #5
          Originally posted by jlevie View Post
          That tach reading in 5th is about right for a 4 cylinder coding plug in the cluster. A PO could have swapped the cluster.

          If someone swapped in a 4.10 diff in place of the 3.73 that a manual transmission car would have, the engine would be turning right around 4000rpm at 80mph. Seems like you are seeing greater engine speed, which might best be explained by the wrond cluster coding plug.
          The car is a 5 speed, so it must be a 3.73. Most likely the cause is that they must have replaced the cluster with a 4 cylinder one. So, how do I get it fixed? Where do I get the right cluster coding plug? Thanks guys!

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            #6
            Is the valve adjustment a fairly simple task or should I just have a professional do it? I already ordered the Bentley manual and I was thinking I would adjust them myself, I have never done a valve adjustment but I tend to work on all my cars so I think I have enough mechanical knowledge to tackle this job. I have done several turbo kit installs and I recently did a supercharger install on my e39 540i 6 speed.

            Comment

              #7
              Read the bentley and judge for yourself. It sounds like you know your way around a BMW. In fact i'll make you a deal. You put a S/C on my 540, and i'll adjust your valves
              Originally posted by KingB
              Scratch my back and I buy a prostitute for you, to rub your balls. HAHA now thats some funny shit.

              Comment

                #8
                Originally posted by HST View Post
                Read the bentley and judge for yourself. It sounds like you know your way around a BMW. In fact i'll make you a deal. You put a S/C on my 540, and i'll adjust your valves
                Yeah sounds like a deal, :up:

                Comment

                  #9
                  Just crawl under your car with flashlight and a wire tooth brush and see what diff you have. Takes 45 seconds dude.

                  Comment

                    #10
                    The coding plug part number can be checked with a little research on http://www.realoem.com. If, as I suspect, it is the wrong plug you can try to get one from a salvage yard, or get a new one from your dealer.
                    The car makes it possible, but the driver makes it happen.
                    Jim Levie, Huntsville, AL

                    Comment

                      #11
                      Originally posted by EMRtek View Post
                      The car is a 5 speed, so it must be a 3.73.
                      That's odd, my 5spd has a 4.10 behind it ;)

                      Just because it should have come that way from the factory 20years ago doesn't mean no one changed it at some point.

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                        #12
                        Originally posted by scabzzzz View Post
                        Just crawl under your car with flashlight and a wire tooth brush and see what diff you have. Takes 45 seconds dude.
                        OK, well I still don't have the car with me, that is why I have not been able to do that. I had to leave the car at a friends house because the car was not local and I didn't have anybody available to drive the car back home. My friend is bringing it home tomorrow, can't wait to have it here.:D

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