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Idle-control valve - sticky? busted?

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    Idle-control valve - sticky? busted?

    Last time I took the Volvo out, it was dodgy to get started, but after feathering the throttle for the first couple of minutes, it seemed mostly OK after that. A bit stumbly at the lights, but not a lot worse than usual.

    This evening it just would not idle, couldn't get it to sit there without using the accelerator. Note that there's some oil on the underside of the intake manifold where the idle air adjustment screw lives, and I do half wonder whether that pin-sized intake might be gummed-up; which could be the start of my worries.

    Anyway, went & grabbed a laptop, plugged it in, quickly browsed around and couldn't see anything that it was complaining-about with the idle control valve (Falcon EEC-IV type); I was pretty sure it wasn't doing anything much, so I messed with the frequency. I then flipped the polarity setting; suddenly the revs surged & it wasn't rock-solid but went up to about 2500rpm.
    So flipped the polarity back to the correct setting - and it was fine for the next 75 minutes of driving.

    So - I suspect maybe I un-stuck the valve by reversing the polarity - does that sound right?

    Any idea on whether this means the valve's on the way out, should I get a replacement? Or do they stick occasionally & when unstuck they're fine for yonks?

    I did pull it to clean it on the weekend (after the dodgy startup last time) but it was dead clean (and I don't seem to have any of the carby-cleaner I thought I have) so I just reinstalled it. Mind you, it was really really clean, and the rest of the intake tract has a thin misting of oil on it ...
    Soft roaders represent an excellent compromise between the needs of the hardcore 4x4 user and the convenience of a city hatchback. Its clear to see why they have become so popular in todays society.