High idle, vacuum leak???

  1. L-plater Joined: Jun 2010 My house! Posts: 69 S2 106 Rallye - Bianca
    #1
    In need of some wisdom...
    My car currently has a high idle ~2000rpm cold - 1600rpm warm.
    I thought this was the ICV so gave that a clean, with no improvement.
    So yesterday I tried seeing if it was a vacuum. Disconnected the brake servo and the pipe to the head breather thing. With them both disconnected it idled 1600rpm but then when I put my fingers over both holes in the inlet, the idle dropped to ~900rpm. So looks like I’ve found my problem. Question though are there anymore vacuum pipes on the inlet? As if not, can the brake servo cause a leak from within the unit itself?
  2. Frequent Poster Joined: Apr 2012 Doyncaster Posts: 783
    #2
    What model saxo?
  3. L-plater Joined: Jun 2010 My house! Posts: 69 S2 106 Rallye - Bianca
    #3
    Its a 106 gti.

    So I had a quick play today, covered up the vacuum pipe to the head breather pipe bit, and the one on the underside of the inlet plenum (I believe this is the vacuum pipe for the charcoal canister), and nothing. still idling at 1600rpm when warm.

    If I put my hand over the throttle body, the car bogs down, but then recovers to the correct idle speed around 900rpm, but then as soon as you blip the throttle it returns to 1600rpm, so no idea!

    Suggestions are welcome, im getting fed up of the stupid thing.
  4. Frequent Poster Joined: Apr 2012 Doyncaster Posts: 783
    #4
    So you've blocked the charcoal canister breather, one from the head, one to the brake servo and it idles ok, until you blip the throttle?

    Check the plastic inlet isn't leaking (it's in two halves). Useful if you know someone who vapes and can assist!

    Idle is/can be controlled by a few things, not just the ICV and they sort of work in unison, I've found. If one is faulty, it can be a bit of a pain to try and eliminate. However, you've cleaned the ICV - I wouldn't rule it out, that it is duff.
    Disconnect the ICV wiring plug. The ECU should then use TPS and Map to control idle (I think, been a while). It might not be 100% but possibly better. This could rule in/out the ICV itself.
    Also reading live data can tell you what is going on. You can see the ICV cycles/map values/throttle angle and find out which one is fluctuating enough to increase idle. Otherwise, I'd just be unplugging each one in turn (ICV, TPS, map) to see what happens. Obviously after you've ruled out any air leaks.

    Failing all of that, sell it. They are worth silly money these days.