Engine revs by itself...

[ALE 111s]

Started he Elise up last night and the engine was revving on its own beteen 1500 and 2000 rpm, drove around the block and still doing it. I turned off and back on and everything normal.

Is this just a case of cold damp weather (not used it for a week) or is something seriously wrong ?

cheers

[Sam_68]

Try cleaning your IAC valve, as a start.

[ALE 111s]

Sam_68 said:

Try cleaning your IAC valve, as a start.

Thanks but what is IAC ?

[shangani]

Idle air control valve.

It sits on the throttle body and alows air to enter the engine at idle when the throttle itself is fully closed. This time of year they get a lot of rubbish in them, causing symptoms exactly as you describe. You unbolt them (easier to remove the throttle body itself in my experience) and give them a thorough clean.

Edited to add - it looks like this:

http://www.eliseparts.com/shop/index.php?main_page...

Procedure for testing / removal etc:

http://wiki.seloc.org/a/Idle_Air_Control_Valve

Edited by shangani on Saturday 24th January 09:11

[Sam_68]

Sorry... Intake Air Control Valve. It's an electrically operated valve fitted to the throttle body that controls the idle speed by opening let just the right amount of air through at idle. They are notorious for sticking.

Cure is to take them off once in a while (be careful - it's easy to drop the screws!), clean them up with a little petrol or WD40 and a clean cloth, then refit.

edited to add: I'm sure it's covered by Shangani's link, but you need to know that after cleaning and re-fitting the IAC valve, you can re-set it's position by switching the ignition on (and immobiliser disarmed), press the throttle slowly and fully 5 times, then switch the ignition off.

Edited by Sam_68 on Saturday 24th January 09:16

[ALE 111s]

Sorry for the delay, been a busy weekend. Many thanks for the detailed advice, will give it a clean when I get a chance.

[lee111s]

Also try resetting the Throttle Position Sensor

[nomisesor]

I'm not an expert but if the suggestions above don't fix it, check for unauthorised air entry into the inlet manifold - when I owned a Civic type R & had a supercharger fitted (in the CTR, not an elise unfortunately!) unknown to the installer the bolts he used were of low quality - one or two sheared and the first symptom was exactly that. Air leaking in affecting the idle.

[Justin S]

I had an issue with tickover a while back.Ended up I knocked the breather hose out the rocker cover with takes the fumes back to the inlet manifold..............