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Jerry-rigging an IAC to avoid engine cutting when idling

  • 29-06-2012 2:56pm
    #1
    Banjo
    Registered Users, Registered Users 2 Posts: 10,485 ✭✭✭✭


    Hi DIYers.
    I have a 2004 Ford Focus. Due to a PCM/ECU problem, the IAC opens fully all the time, causing the engine to hit 5K+ rpm at idle. Disconnecting the IAC has a polar opposite effect - the engine can't idle at all, to the point that if it's out of gear for more than a few seconds or not being fed gas, the engine cuts out. It's driveable-ish but when slowing down to a stop at junctions or in heavy traffic it tends to cut out.

    Longterm I need the ECU repaired/replaced, but it's going to be the guts of 2 weeks before I can get that looked at. I could, in the mean time, connect a resistor in series with the IAC to restrict current flow so the IAC opens partially but I can't really do that right this second.

    So, as a really short term solution does anyone have a suggestion for how to get the IAC to stay partially open so it'll idle without cutting out, but not rev like crazy so I can drive it home without needing to keep constantly restarting the engine?

    The default position under no current is closed.
    The piston that closes the valve is spring loaded, so cannot be pushed into a partially open position.
    Both sides of the valve connect to holes coming out of the engine block, there's no visible tube that I can pinch.
    Equally, since I don't know where either of the holes go I don't really want to prop the valve partially open in case whatever I use shakes loose and falls into the engine.

    I have access to a cheap 8mm socket wrench, a Spar shop and the internet. No duct tape or MacGuyver knives I'm afraid.


Comments

  • #2
    ARGINITE
    Registered Users, Registered Users 2 Posts: 2,719 ✭✭✭ARGINITE


    Super glue it partially open?


  • #3
    mickdw
    Registered Users, Registered Users 2 Posts: 23,688 ✭✭✭✭mickdw


    We had an audi 100 years ago that wouldnt idle at all once warmed up. We drove around it for awhile. Easy enough to drive around it in the short term.


  • #4
    Banjo
    Registered Users, Registered Users 2 Posts: 10,485 ✭✭✭✭Banjo


    Superglue might do the job but it would wreck the part. Thanks for the suggestion though. I just avoided slowing down on friday, put a resistor in series at the weekend and it's running OK now except when starting from cold. Should get me through until I can get the ECU looked at.

    Anyone have any experience of using Autokey out near the N7?


  • #5
    AzureAuto
    Banned (with Prison Access) Posts: 233 ✭✭AzureAuto


    Disconnect the brake servo pipe ging to the inlet manifold. This will cause air ingress past the closed throttle body, but will most likely run like a dog, if its only a short term solution you need. Bear in mind, the brakes wont be great though!!


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