Hi, I have a little problem with my idle. Normally when I start the car from cold the idle is around 1000 rpm then as it gets warn it settles around 680 ish but the last week or so after I have been driving about 20 mins when I come to a stop it idles at 1000 even though its up to temp?? When I get home and turn the car off, if I turn it straight on again it goes back to 680? Any ideas? Thanks