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C20XE Ignition Problem

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  • C20XE Ignition Problem

    So, as many of you might have seen, I'm having a lot of trouble with my C20XE m2.5... The last thing I diagnosed was the ignition timing. basically i managed to hook up the car to Op-com diagnostics, and on the program it says that at idle, the spark occurs at 20 degrees before TDC (top dead center). According to haynes manual, the spark should occur between 8-12 degrees, and if you slam on the throttle you get advance of up to 20 degrees. When I slam on the throttle, the ignition advances up to 30 degrees (even 33 on one occasion). Basically what I have is a very slow and unresponsive car. I have to release the throttle pedal to get any acceleration. Why might this be happening? Spark plugs, HT Leads, Rotor Arm and Distributor Cap have been replaced, no difference.

    -Everything is standard, apart from the banjo bolt which is drilled to 2mm. the car was slow even when the banjo was factory spec.
    -There?s a lot of vibrations and the engine is very noisy, it idles perfectly though, 1000 RPM (+50 cuz of the drilled banjo)
    -The engine is very noisy as I accelerate.

  • #2
    Anyone please? Does it sound like knock sensor problem ??

    Here's live data from my engine. Looks like instead of advancing the ignition point as I apply the throttle, my ECU delays it... Why might this be happening?
    Click image for larger version  Name:	engine dg.jpg Views:	1 Size:	1.91 MB ID:	521340

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    • #3
      DarrenH , do you have any idea or any info, if the base timing is set to 20 deg bTDC (on idle)?

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      • #4
        it will only knock under heavy load (engine doing allot of work) at medium to high revs, it wont be knocking at idle when jabbing the throttle. Also, ignition advance is computed using engine load and rpm, again, there is no load at idle.

        Idling

        When idling, a characteristic curve dependent on engine speed becomes effective, which is corrected by the idle speed control program component of the CPU:

        If engine idle speed falls below the nominal value, the ignition is 'advanced' to raise the engine torque.

        If the engine speed rises above the nominal value, the ignition is 'retarded" to reduce engine torque.

        Anti‑Jerk Function

        The control unit recognises jerking by comparing the engine speed at two short consecutive intervals, filtering the values and computing the difference.

        If the engine speed is rising, the ignition is 'retarded' to reduce engine torque.

        If the engine speed is falling, the ignition is 'advanced' to increase engine torque

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        • #5
          Okay so I managed to find 2 other C20XE engines, which seem way faster than mine, and I ran diagnostics on those engines.
          The main and only difference between my engine and the other 2 was the BASE timing.
          On idle: My engine ignites the mixture when the piston is at 20 degrees before TDC at idle, and the other two engines do it at 16 degrees(again remember, this is IDLE). So basically my engine has too much advance, and it knocks, which explains the loss of power, vibrations and noise. I checked the timing belt, it all lines up perfectly, so nothing to do there. What else could possibly affect the BASE timing guys? Why does my engine has more advance? I tried running different ECU, it doesn't make a difference at all. Also, is there ANY way to retard the timing by 4 degrees with some sort of a 'hack', or aftermarket ignition coil/amplifier or module

          (I also replaced the knock sensor, without any success)

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          • #6
            i think you are wrong to presume that because it has 4 degrees more advance at idle, then it has 4 degrees more everywhere. the advance is completely dynamic and computed on the fly, it is not a linear advance system, for that same reasons cant be "undone" mechanically.

            have you tried turning the ECU coding plug round (brown plug with A and B on it)

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            • #7
              I have switched the plug yeah, made no difference.
              looking at the graph above, it all makes sense, my engine is pinging where it shouldn?t (even below 2K RPM)
              Also I have tested my engine and the other 2 at all conditions (from a cold start) and at operating range, and their base timing is always 16c bTDC, while mine is always 20c bTDC.

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              • #8
                Okay this is freaking unbelieveable!
                I swap out the entire engine loom with sensors (except crankshaft), and I upgrade my engine management to Motronic 2.8. The ignition advance problem still persists, at idle it sitll sparks too early (20c bTDC) instead of 16!!

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                • #9
                  My car(engine) is Stefan- Calibra, and my friend's is Toni-Astra... Look at the difference (at idle)

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                  • #10
                    could be EMF (electro mechanical interference) on the crank signal. i have witnessed it myself, but admittedly was on aftermarket management. (but standard sensors)
                    Last edited by DarrenH; 25-07-2018, 01:16 PM.

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                    • #11
                      Originally posted by DarrenH View Post
                      could be EMF (electro mechanical interference) on the crank signal. i have witnessed it myself, but admittedly was on aftermarket management. (but standard sensors)
                      you mean electro magnetic? and EMI instead of EMF.. or ?

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