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S14 hesitation at WOT

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  • #76
    Terence237 Yeah I swapped coil early on.

    basketcase I have been going back and forth with this same thoughts - rings. I am not sure my else is left. Quadruple checked all my work.

    I borrowed a friends' M3 to try a few things. Swapped ICV last night (which I had previously done as well) between the cars. ECU next (stock chip). I am going to get compression and leakdown on the said car, as well just for comparison. Log some of the data plots, i did earlier.
    Current: '95 E34 540i/6 Hellrot/Pergament | '88 E28 ///M5 Schwarz/Natur | '85 E23 745i Diamantschwarz/Buffalo
    Past: '83 E28 533i/5 Schwarz/Schwarz


    • #77
      Originally posted by basketcase View Post
      Been thinking about this. I've had over the years bikes and cars with low compression/bad rings that have similar symptoms to you. Like under any type of load (ie AC on) the engine would die once clutch is let out. At high revs the engine would operate fairly normally.

      Low compression = low torque.
      Your leakdown figures and compression figures are to me obviously an issue with this engine. 160 psi compression? Mine was 230 after a rebuild, and that's a common figure for s14s. 160 psi is stock figures for a e30 325i M20 engine, which has 8.8:1 compression from factory.

      Also your leakdown figures of 25-30% to me indicate an issue. I regularly do leakdowns at work (I am a BMW technician) and the norm for a engine with no issues is 5 or 10%.

      You have replaced everything on the engine... Maybe address the mechanical issues and retest after. Ie new rings.
      I'm new here so forgive me for jumping in, but this. I mean, you're rolling each piston to TDC compression for each individual leak down test and locking it there, yes? If so and 25-30% loss of pressure- the engine needs love... Flip side, engine will run WAY better.


      • #78
        I would still try swapping in stock ECU with confirmed factory chip along with the stock cam gear with correct timing and see what happens as a last ditch. Definitely sounds like the motor is due for a refresh though...

        Also you could do a wet compression test and compare the numbers to dry. I believe you just need a tablespoon of oil down the cylinder then crank 6 more rotations per cylinder and if the numbers go up the rings are probably no good.