Recently invested in a new IAC (idle air control) valve for my Renault Laguna. The car had been misbehaving with irregular and 'racing' tickover, particularly when cold. My local Renault dealers wanted a staggering £45 + vat to run a diagnostic check, this in itself would have been a waste of time and money, as this fault will seldom register on the diagnostic printout. They then stated that if indeed the IAC was found to be at fault, the part alone would cost £106 odd, plus labour, plus VAT! Most main dealers, Renault included, will want to sell you the complete unit including the throttle housing. The thing is, the housing is unlikely to be at fault... Will just want a clean when the IAC is removed! The fault will almost certainly relate to just the valve (they get a carbon build-up and then the problems outlined begin). Anyway, on advice from a mechanic friend, he told me to lift the number from the offending part (found by the electrical connector block), and have a look on eBay for just the IAC... NOT a complete unit. Pleased to say, easily found, brand new with a 12 month guarantee for a very modest £20 + p&p! Quite a difference, I think you will agree! Whilst looking, found this part readily available for most makes at a similar price.
Now to the point of writing this guide...
It is no use simply changing the valve without following a reset procedure!!! I made this mistake and what should have been a 5 minute job became a pain as the original fault remained after fitting the new valve.
The following certainly applies to Renault, Vauxhall and the majority of other makers:-
Idle Valve Reset Procedure
When fitting a new idle valve, ensure that the internal throttle housing is cleaned well.
Once the new valve has been fitted, switch the ignition on, DO NOT start the engine, leave for 10 seconds, turn ignition off, repeat 3 times.
Only then, start the engine and take for a drive.
If you follow the above procedure, chances are all will be well, problem solved!
Although these valves are readily available, I found no reference to the above either in eBay listings or indeed with the part I received.
It really is a simple, inexpensive DIY job that saved me a fortune... As long as you have all the info!
I estimate the final bill from Renault would have been around £200... It should cost you no more than £20-25 to buy the valve and take less than 10 minutes to complete... But remember to RESET after installation :o)