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M20 Knock?/Piston Slap? Need Help! (Video Inside)

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    M20 Knock?/Piston Slap? Need Help! (Video Inside)

    Car Info:
    1989 325i 5 Speed
    Purchased from AL, PO claimed the car had a blown head gasket between cylinders 5/6. After a compression test, all cylinders showed around 160 lbs.
    I have seafoamed the car and I am using 93 octane fuel. The car will randomly give the code 1223 (Coolant Temperature Sensor) at times, and other times it will give code 1444(No Error)

    I have replaced: Distributor cap, rotor, plugs, fuel pump, fuel sending units, fuel tank, fuel filter, vacuum lines, cleaned ICV, valve cover gasket, oil pan and gasket, adjusted valves, coil (used), guibo, O2 Sensor (used)

    I think I need to replace the fuel tank breather (PN: 13901711395)

    So I have searched and so far, I'm thinking my problem is a piston slap issue, but I think the noise I'm experiencing may be too random to be piston slap. I don't know where to move next and I'm considering having another head rebuilt to bolt on or just sourcing a running M20. Any help or advice would be greatly appreciated! I'm eager to get the car running by summer!

    The problems I am having include an intermittent surging and knocking. The two do not seem to be directly related but I'm not positive. The car doesn't want to rev much higher than 4k. Once the revs get around that area, power cuts out and the surging is very apparent. The knocking isn't a broken rocker arm, I have checked multiple times. I will re-adjust the valves this weekend, because they do sound a little loud to me but that won't address the random knocking. See the videos below.




    #2
    Same problem is being discussed in a different thread, same noise is happining to me too.
    "I wanna see da boat movie"
    "I got a tree on my house"

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      #3
      The first thinks I'd think of for a loss of performance above 4k would be the ignition wires, wrong plugs, fuel system, and TPS. Rarely, the DME can be "browning out" from a bad fusible link.
      The car makes it possible, but the driver makes it happen.
      Jim Levie, Huntsville, AL

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        #4
        So would it be better to go ahead and buy another motor to swap in before purchasing a TPS, ignition wires, and new plugs? Or should I do those things first, and then another motor? And could clogged injectors be the problem with the fuel system that is causing the loss of performance? Thanks for the info btw!

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          #5
          Even if you you change engines, the new engine needs a good TPS, ignition wires, and plugs. So money spent there isn't wasted.
          The car makes it possible, but the driver makes it happen.
          Jim Levie, Huntsville, AL

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            #6
            ok have you had the valve cover off, I just had the same noise and it was a rocker arm keeper slid forward, it runs perfect now but don't know if I got the keeper right, what is the dog leg portion of the keeper? It seems to be tight. I'll need to drive it to see

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              #7
              I dont know if this will help, but i had a rattle knocking sound that was random at idle, consistence at 1500-2300 rpm and silent above. tried to listen to all parts of the engine, ended up being a shitty waterpump bearing. what was strange is that i didnt sound like it was coming from there, but since changed, no noise.
              1987 325iC/5 Alpine White/Cardinal
              1988 325iS Lachssilber/Natur
              sigpic

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