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High idle

Discussion in 'E30 (1984-1993)' started by az3579, May 1, 2010.

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    az3579

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    My engine idles at 1000rpm, all the time. When cold, a little higher, but that's expected. After warming up enough, it drops to 1k again.

    I had a smoke test done and no smoke came out from anywhere it shouldn't have, so it's not a vacuum leak that I can tell.


    I've been told it might be the Throttle Position Switch, or that it might just have to be adjusted. Could there be any other culprits?
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    mooseheadm5

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    Not much you can do about the throttle switch. What chip do you have in the ECU? Is it a Turner/JimC chip? I think they tend to idle them high, as my wife's ti idles around 1100 because I specced a lightweight flywheel.
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    az3579

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    The chip in the ECU is factory chip. I already knew this as I took the ECU out to inspect; it was clearly unopened. After opening I only confirmed it.

    I recently just cleaned the ICV and checked the resistances of the TPS and both check out fine and are functioning correctly. I do have a lightweight flywheel, but a stock BMW chip wouldn't adjust the idle for that, would it?
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    mooseheadm5

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    It shouldn't adjust for the flywheel. Check to make sure you have no vacuum leaks. It is common for the intake boot to crack where the fittings for the idle air go in or for one of the O rings at the idle valve fitting or PCV on the valve cover to leak air.
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    az3579

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    I had a smoke test done and it revealed no vacuum leaks. The Intake boot is brand new, and to double check, I visually inspected it, and still looked new. The hoses going from and to the ICV look brand new as well with no cracks or imperfections. The hose going to what looks like the valve cover (goes from the intake boot, correct?) is very dirty, though it doesn't look cracked either. I'll pull that hose, clean it, and inspect further, but I doubt that's it. It was loose when I reinstalled the ICV and the idle was horrible, so I adjusted it and now it's fine; I assume if there still was a leak, it would still be running badly. As I said, I'll check that one again.

    BTW, what is a PCV?
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    MGarrison

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    az3579

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