High idle speed

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High idle speed

Postby bobface » Thu 27.09.2007, 15:11

Guys,

I've read a good few posts here about high idling, my s2's just started doing it recently. It doesn't seem so bad today (was idling at 2500 yesterday). Attached is a cold start e/s.

Coolant temp sensor seems to work correctly (however i can get boost immediately after cold startup, all the way to 0.6, i didn't think ECU was supposed to let you).

Sadly i tried to take it out a little spin shortly after this, but my laptop crashed. Can anything be learnt from this?

Other thoughts?

Shaun
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Re: High idle speed

Postby paulwatkins » Thu 27.09.2007, 15:56

bobface wrote:Sadly i tried to take it out a little spin shortly after this, but my laptop crashed. Can anything be learnt from this?


Get a new laptop! :-D

In all seriousness Shaun, get access to the manuals section and have a look at the Engine Management Manual. Its a really good reference for fault finding.

It could be the IAC valve sticking/faulty. The purpose of the IAC valve assembly is to control the engine idle speed.

It would appear that a number of idle speed issues seem to be coming up; I'm wondering wether a particular component - the IAC valve or other - is coming to the end of its ~15 year useful life! :?

But have a look through the manual first and try some fo the fault finding suggestions in there.

Paul
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Postby ESM » Thu 27.09.2007, 17:21

The no.1 cause of a high idle is a leak from the intake plenum.

The most common source of the leak is the pipe that comes off the rear edge of the plenum just to the left of the throttle body (as you face the engine). The is connected via a 90° piece that often degrades and splits. The 90° bit can be removed and the pipe attached directly.
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Postby ESM » Thu 27.09.2007, 17:32

Just looked at the log and I think its a leak; the IAC is at minimum opening but the manifold pressure is still highish for idle (0.4bar compared to 0.3 to 0.35bar or so typically). Everything else looks normal.

If its not a simple leak / pipe fallen off then look to the IAC valve. Check connections, fuses and cleanliness before forking out for a new one, its not a common failure.
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Postby bobface » Fri 28.09.2007, 15:22

Thanks guys,

I checked the pipe outlets on the back on the plenum near the throttle body, i dont have a 90 degree pipelet, just a straight pipe on the right of the two stubby little outlets. I pushed this on further but it does look pretty crappy, made a little difference but probably needs a new pipe.

I've read elsewhere the left hand side outlet is for a recirc dump value, and if i dont have one (which i dont) i should be plugged up? Mine is nice and open. If i were to plug it, what's it supposed to be plugged with? Is there a standard B&Q rubber doofer that would do the job?

S
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Postby paulwatkins » Fri 28.09.2007, 16:15

bobface,
You should have a rubber stopper on that unused nipple and IIRC its held on by a little clamp.

Any motor factors should have something suitable. If you cant find one, let me know and i'll send you my old one.

I've got a dump valve fitted and now use this connection on the plenum
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