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Erratic idle

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  • [Corsa C 2000-2006] Erratic idle

    Engine all running, and taken it for few drives to get exhaust etc and tracking.

    I have eml light on the dash, and for some reasons codes aren't clearing?

    That's aside, my idle is erratic. Sometimes it's ok, but if engine is revved when they needles comes down it drops to around 400rpm and obviously starts struggling.
    I've checked vac hoses I can find, and all seem OK. They don't have idle control valve so don't know where to look next really.

    I've included a video of speedo below. When revs drop you can hear the vibration from tools on rocker cover as engine shakes so much.

  • #2
    What code(s) are showing? They won't clear if they are current - or do you mean with the engine off they won't clear at all?

    I've had this happen and needed to get the ECU flashed - nothing else would reset the idle to a reasonable level. Quite good fun getting the idle and idle delay set to just how I want it. (Also - worth mentioning - for some reason to do with Murphy's Law the number of times throttle bodies get some crap into them after surgery - even though you've been meticulous with cleanliness.)
    1972 Viva restoration thread -


    • #3
      It idles nicely, it's just that after you take foot off accelerator - either revving or driving normally the idles drops really really low.

      They codes don't seem to clear at all. Not sure how long you're supposed to leave leads off battery though?


      • #4
        I thought you couldn't clear the codes on the ECU for a Corsa C by disconnecting the battery.

        What codes are showing?


        • #5
          Originally posted by Hardcore View Post
          I thought you couldn't clear the codes on the ECU for a Corsa C by disconnecting the battery.
          Precisely - you can leave the battery off all week and the codes will stay in there. That may affect the idle issue you're having - depends on the codes.

          You can only clear the codes with diagnostic kit - eg Opcom

          A sticky throttle body can cause the idle to struggle when you come off throttle. It's because on over-run the fuel is cut off and the throttle shuts beyond idle setting. As the ECU senses the dropping rpm it should open the throttle slightly - but if it's sticky it just doesn't move quite enough. The idle as set from a start up doesn't have that same effect.
          1972 Viva restoration thread -


          • #6
            Thanks Taurus. Took aprt dash and found the diag olug.

            Git loads of codes to start with,


            I then cleared those and let car idle. Did not drive it.

            Here's what come back


            So I checked live readings of afm and it's a flat 0


            • #7
              If you haven't already maybe check the connections on the MAF and the plug from the loom that goes into it in case one of them is corroded a little. If not i'm guessing the MAF sensor is fubar.


              • #8
                Yeah, I did have a look. Pins seem OK. Going to test power is getting to plug tomorrow then take from there.

                Good news really, should sort it all. Easier now have diagnostics port access again lol.

                Not looking forward to swapping this abs pump at all