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M42 vibration damper failure?

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    M42 vibration damper failure?

    The rubber ring on my M42 vibration damper has a hairline crack encircling the entire ring. Seems like this could cause problems when it warms (and if it flexes around the crank axis) but I'm just guessing. Anyone on here know what it takes for the rubber to fail enough to cause problems? I'm fishing for the source of the following problem:

    Car starts, sounds, and idles fine when cold. Poor engine response to acceleration though, and response worsens as engine warms. Car stalls after moderate to hard acceleration when warm. May briefly restart, but dies immediately. DME relay seems to still be clicking on restart attempts. Check engine light works but isn’t illuminated after stall. Stomp code = 1444. Car restarts on the first try if I let it sit a few hours (not fun on city freeway with no shoulder though.

    Car's current condition:
    - dashboard temp needle moves, but never past half-way mark
    - tiny coolant seep (not dripping) under intake, but coolant level is pretty steady
    - resistances of crank, cam, and throttle position sensors and coils are all normal
    - spark plugs are a few months old
    - air hoses, IAC valve, air filter, fuel pump, fule filter, and fuel pressure regulator are <1yr old
    - I installed a spare AFM, but get the same problem
    - mechanic installed timing components <1 yr ago
    - leaks oil, but I keep it above half full
    - belts are two years old, no cracks
    - Recently been hearing a faint, brief chirp when pulling away from a stops
    Attached Files

    #2
    I don't see the crack in the photo...are you referring to the rough edge where the rubber meets the metal? If the damper was failing, I think you would know because it would probably make a hell of a lot of noise as it bangs around. Maybe try pulling by hand on the outside of the ring to see if it is coming apart? Whatever the case, I do not think that this is the cause of your problems.

    Have you physically inspected the coils? I had an issue once where the car ran poorly after warming up, and it was because one of the coils took a dump, but it only operated improperly after warming up. When cold, the coil's internal wires were making contact and working. Once it warmed up, thermal expansion caused things to grow and cause an open-circuit, meaning no spark on one cylinder. Upon inspection, the plastic/epoxy body of the coil had bulged and oozed molten plastic in one spot.

    The other thing to check is the fusible link. In the trunk, you will see 2 wires coming off of the battery's positive terminal. One is huge, and one is not as huge. The huge one is for the starter and charging circuit. The not as huge one is for the fuel injection system, and they are separate circuits. This second wire has a 50A inline fuse on it about 12 inches from the battery (to inspect it, you have to pull the carpet, the black plastic shield on the wires and the shrink tubing covering the fuse). It seems to be a somewhat common problem to have this connection fail due to moisture intrusion in the trunk...the wire corrodes where it is crimped into the fuse and starts acting like a random open circuit. It could be that this is failing as things warm up. But, to inspect it you have to cut off the shrink tubing, and you will need to re-wrap it in some heavy duty electrical tape when done. When mine failed a decade ago, I chopped an extra fuse out of a junk yard E30 and spliced it in.

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      #3
      Good advice. Yes, I was referring to the rough edge where the rubber meets the outer metal. I heard no noises before or during the stalls, and the rubber feels sturdy when I yanked on the outer ring, so I'll move on for now.

      The coils have been on the car at least as long as I've owned it (5 years), probably much longer. Took a look at them, plastic bodies on two have white blotches (see photo), the other two have moist blotches on the plastic too. They were all 0.7-0.8 ohms before running and after idling in the driveway. I'll have more time tomorrow to drive it around longer and remeasure, and pull off the bolts holding the coils to inspect them better. The m42 DME doesn't have a stomp code for bad ignition coils, right?

      I found the wires in the trunk. I'll see what the wire looks like under the shrink wrap tomorrow.
      Attached Files

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        #4
        Hmm, hard to tell if that is just dripped corrosion, or if the coils are crapping out. They would ohm out properly when cold if there was an internal break that only opened up when hot. Maybe try unbolting and cleaning them to see if the plastic bodies are damaged.

        It could also be that the plug wires are worn out and arcing through the insulation. That might also be thermally dependent behavior. But, at this point my money is on the coils since they do look sort of cooked.

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          #5
          hi bmwman91 do you know if the harmonic balancer and crank pulley is interchangeable from another car say like the m44? I'm in the market for a new harmonic balancer but having trouble finding one for the m42.


          Thanks
          Ivan

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            #6
            It is definitely not a direct swap since the E36 M42/M44 uses serpentine belts, and the E30 M42 uses V-belts.

            According to RealOEM, the E36 M42, M43 and M44 all use the same part number for the crank damper/pulley, so functionally I would think that it should be fine since the teeth on the outside of the damper ring are positioned correctly, and they are the most important part (for crank position and speed sensing).

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              #7
              Thanks appreciate it


              Sent from my iPhone using Tapatalk

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                #8
                Well, I drove it around for several 30-40 min loops around the neighborhood and it ran pretty good actually. However, coils 1 and 2 were at 0.8-1.2 ohms after these loops, 3 and 4 were at 0.8 ohms. All dropped to 0.7-0.8 within a few minutes of the engine off. I was kinda hoping it would stall and I could ohm them immediately after.

                The small wire from the + battery terminal looked very clean under the shrink wrap.

                Is it time to retire my "BMW" spark plug cover and switch to the hqautosport COP kit?

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                  #9
                  I'd say that you should just find another local M42'er to swap coils with to see if it helps, but I am not sure how many other M42'ers there are on the island! So on the one hand, the coils do look sort of pooped, but on the other hand it is never good to start throwing money at a problem with unknown cause.

                  I think you should pull the coils, give them a good cleaning and take more photos if the bodies still look deformed or discolored. If so, then sure, go for the COP conversion (it is more than just bolting the thing on, you will need to trim the wire harness to do it properly...I think that the crimp terminals are just Amp Standard Power Timer ones).

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                    #10
                    just experienced an m42 vibration damper failure...my symptoms were a lot more severe, car wouldn't even start.
                    1991 318is ---230K - DD
                    1991 318i ---- 308K - retired

                    Originally posted by RickSloan
                    so if you didnt get it like that did you glue fuzzy oil to the entire thing?

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                      #11
                      Yeah, I need to find some other m42ers out here! Car ran great tonight for an hour straight, no stalls, power seemed pretty good. I unbolted the coils after and started cleaning them. I don't see any bulges in the plastic, just some baked crap on the plastic where the plastic meets the outer metal. Not sure what to make of this inconsistent issue. I'll try running it even harder tomorrow after work.

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                        #12
                        i've been trying to diagnose my no start issue for over 2 months...I previously had checked the damper, and it didn't seem out of sorts, however during the repeated trying to start it, it finally had a visible catastrophic failure. So while it might look good, it doesn't mean it necessarily is
                        1991 318is ---230K - DD
                        1991 318i ---- 308K - retired

                        Originally posted by RickSloan
                        so if you didnt get it like that did you glue fuzzy oil to the entire thing?

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                          #13
                          What failure did you have jrobie79? I have some slight vibrations in mine not sure if it's my damper that's worn or the other pulleys are worn. I know the A/C pulley is kind of suspect last time I had everything apart.


                          video, sharing, camera phone, video phone, free, upload

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                            #14
                            the two pieces literally separated from each other, so the crank would spin the pulleys, while the toothed ring skipped, fucking up my ignition timing/etc. The CPS would receive inaccurate/intermittent information, hence the no start.
                            1991 318is ---230K - DD
                            1991 318i ---- 308K - retired

                            Originally posted by RickSloan
                            so if you didnt get it like that did you glue fuzzy oil to the entire thing?

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                              #15
                              Same thing here, I went nuts trying to figure out how timing could be off on the crank yet on from cam/FW. Then I removed my dampener/pulley to see if the woodruff key or pin had somehow broken only to readily discover the issue.

                              My car would not start when it failed, and rotated about 1", only pop and sputter.

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