idle speed

ninja · Post by **ninja** » Fri Apr 21, 2006 11:47 am

most of the time when i start my car it idles at about 900 rpm

but occassionally it'll start and idle at 2000prm bouncing up and down between that and 1500rpm

other times it will bounce between 500rpm and 900prm and then cut out when it goes back down to 500 rpm

what the hell is going on?

all i need to do is stop the car and start it again and it's fine!

ninja

mac · Post by **mac** » Fri Apr 21, 2006 11:54 am

Give the idle air control valve a clean.

I would offer to do it for you, but I managed to break mine in the cleaning process

ninja · Post by **ninja** » Fri Apr 21, 2006 11:56 am

lol

where's that then?

the car is getting seviced at jude performance in a couple of weeks so i'll ask dan to do it if i can't find it myself

ninja

mac · Post by **mac** » Fri Apr 21, 2006 12:20 pm

It's a wee black thing, located on the engine side of the plenium, is held in place with 4 torx headed machine screws and has a multi-plug hanging of the back of it.

For the s2 there aren't mega expensive for replacement units <£30 from eliseparts

The_Rossatron · Post by **The_Rossatron** » Fri Apr 21, 2006 12:21 pm

every time my car's had a dodgy idle, usually after the battery has lost a bit of charge I've done the old 5 pumps of the accelerator pedal things and it's sorted it with a rock steady idle.

1. Turn ignition to position 2.
2. Depress the accelerator pedal 5 times fully and slowly.
3. Turn ignition off, take key out.
4. Start you car.

I was told this didn't work on S2s but its definately made a difference on mine.

Post by **Shug** » Fri Apr 21, 2006 12:21 pm

mac wrote: For the s2 there aren't mega expensive for replacement units <£30 from eliseparts

Handy really, if you spend your spare time 'cleaning' them.....

mac · Post by **mac** » Fri Apr 21, 2006 12:23 pm

I cleaned it soo well - that I don't think it wanted to get dirty again.

And I had an erratic idle speed too - hence the cleaning

Post by **Shug** » Fri Apr 21, 2006 12:27 pm

The_Rossatron wrote:every time my car's had a dodgy idle, usually after the battery has lost a bit of charge I've done the old 5 pumps of the accelerator pedal things and it's sorted it with a rock steady idle.

1. Turn ignition to position 2.
2. Depress the accelerator pedal 5 times fully and slowly.
3. Turn ignition off, take key out.
4. Start you car.

I was told this didn't work on S2s but its definately made a difference on mine.

That re-sets the throttle position sensor settings in the MEMS ECU. I've also been told it doesn't apply to the S2 (as it's a totally different ECU), but if it worked for you, then maybe it does?

ninja · Post by **ninja** » Fri Apr 21, 2006 12:27 pm

excellent - thanks guys!

ninja

mac · Post by **mac** » Fri Apr 21, 2006 12:31 pm

The S2 has more of a learning ecu.

It would be worth disconecting the battery for 5 -10 mins, re-attach it and then start the car on the key.

Don't touch the throttle at any time - it should rev up too high, then rev so low that the anti-stall kicks in.

Basicly what it is doing is learning the optimal setting for the IACV. once the car is warmed (ie show circa 80deg on stack) your idle should be nice and the car will be ready to drive.

Next time you start it will know the hot position and shouldn't go through all this procedure.

robin · Post by **robin** » Fri Apr 21, 2006 12:35 pm

The S2 reset sequence involves turning the ignition on and off repeatedly but I cannot remember how many times and how long to wait in between.

In both cases you are resetting the learned IACV setting (as well as a few others) forcing the ECU to work it out again.

A stuck IACV will certainly cause bad idling, as will vacuum leaks (but these don't sound relevant here as the problem is always cured by restarting). I would suspect the IACV.

Cheers,
Robin