Idle Speed Suddenly Too Fast - Advice Please !!!!!!!!!!!!!

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Just Mike - 11 Feb 2005 10:11 GMT

For seemingly no reason at all, my 300SE (W126) has decided to idle at
~ 1200 rpm instead of her usual 600 rpm. She does this hot and cold.
Apart from that she is running and performing as before. What's going
on, where do I start looking to slow her back down?

All help and comments greatly recieved :)
Mike

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W126 300SE
W115 220/8

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T.G. Lambach - 11 Feb 2005 17:26 GMT

Check for simple mechanical possibilities - that the throttle linkage
has free movement over its range and that - don't laugh, it's happened -
the floor mat isn't pressing the accelerator.

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marlinspike - 12 Feb 2005 02:36 GMT

Two possibilities, 1 is way more possible that the other. It's either the
idle control valve, or the idle control unit. I say there's a 95% chance
it's the idle control unit. I know on the 1985 380SE its a black box up by
the firewall, but for some years it's behind the glovebox so yours might be
there. It's a fairly expensive part, so you might want to get a used one (i
got mine from pgauto.com) or look for a refurbished one.
Richard

> For seemingly no reason at all, my 300SE (W126) has decided to idle at
> ~ 1200 rpm instead of her usual 600 rpm. She does this hot and cold.
[quoted text clipped - 3 lines]
> All help and comments greatly recieved :)
> Mike

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