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C20XE No Power, Rough Idle when warm

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  • C20XE No Power, Rough Idle when warm

    So since I bought my Calibra (C20XE M2.5) last year in february, I couldn't make it work properly, the car has no power, and the idle is rough once the car warms up. It's not cutting out but especially if I get stuck in traffic the idle RPM goes lower and lower fluctuating between 600 to 1000 rpm (the ecu whacks the ICV open and prevents from shutting down and it goes on and on)
    Things I have done so far:
    - Replaced spark plugs, cables, rotor arm and distributor cap.
    - Cleaned throttle body like brand new, every single vacuum line is breathing freely, including the banjo bolt that goes directly into the intake manifold.
    - I have tried 3 different ICVs, every single one of them did not make ANY difference.
    - I ran diagnostics software, every single sensor seems to be working properly (TPS, CTS, MAF, Lambda, Hall, Crankshaft).
    - I tried another ECU, from Astra F GSI that was already known to be super fast, did not change a single thing.
    - I raced with Astra G 1.8 (X18XE, 116hp), there is a whole car length between us as soon as we hit the second gear. (repeated the race couple of times, the same results), This proves my engine has some kind of a problem, any help or advice is welcome.

    Here are pictures of the dry compression test that I did, as well as a picture of the spark plugs. The test was done on COLD engine, all spark plugs were taken out, but I did not press the throttle body wide open, just cranked the engine normally. Cylinder 1 (on the picture), is the one closest to the cam belt
    Click image for larger version

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    Compression Test Reults Spark Plugs

  • #2
    Is the tps correct for the engine? Believe some are on/off others are a resistor type.

    Also from experience genuine icv (bosch iirc) tend to allow better operation than other makes.

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    • #3
      Originally posted by James C View Post
      Is the tps correct for the engine? Believe some are on/off others are a resistor type.

      Also from experience genuine icv (bosch iirc) tend to allow better operation than other makes.
      The resistor type are from Motronic 2.8 engines, and yes it is the correct TPS on my car. Also the ICVs that I have tried are all genuine BOSCH. The last one I took out from an already proven to work fine car, and my car did not improve when I installed it.

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      • #4
        do you know anyone you can borrow an entire distributor from and swap it over as a test

        would also suggest replacing those twin electrode spark plugs for standard NGK type

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        • #5
          Originally posted by DarrenH View Post
          do you know anyone you can borrow an entire distributor from and swap it over as a test

          would also suggest replacing those twin electrode spark plugs for standard NGK type
          I can't borrow an entire distributor unfortunately.. I have tried many different spark plugs (BOSCH, NGK, Denso) and they don't influence my engine, so that is not the problem for sure. These plugs are 2 months old.. Next time I replace them I will go for standard NGK.
          What is your opinion on the compression figures?

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          • #6
            Engine looks mechanically healthy to me. To rule out idle control, if you electrically unplug the ICV the idle will be low/ cold and high/ hot but at least stable.
            Is the cam timing correct?
            Also you need to check wiring to sensors, you can't rely on simply swapping units and looking for ECU faults. Like the temperature sensor can be open circuit and the engine wil do wild things before the ECU reports a fault. I drove my GTE for a short journey during which the revs stuck at 3k, then the idle dropped and it eventually stalled and wouldn't start. I'd left the CTS unplugged and forgotten about it.

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            • #7
              What's your take on the breather mod guys? Should I do that, or shoukd I drill the banjo bolt to 2mm?

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              • #8
                Check the timing. Had similar problems with mine and the exhaust cam was a tooth out.

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                • #9
                  Originally posted by GeraldGTE View Post
                  Check the timing. Had similar problems with mine and the exhaust cam was a tooth out.
                  I checked it before, it's fine...

                  I measured the resistance of the CTS, and it was fluctuating around 830 ( I was driving the car for 30 minutes or so ), can anyone give me a chart from the CTS? Thanks

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