My vehicle starts normally with the cold start at 1100 or so revs then drops down to 760-800 at idle, now my thermostat is knackered so it usually runs cool, (around about 70 degrees) But when im in traffic and it reaches about 75-90 degrees, it begins to hunt for about ten seconds, then settles, Its done this on numerous occasions at around the same temp, so im assuming this is where a mixture change happens, Can anybody educate me as to when the mixture changes for a 'up to temp' engine, and any idea why my car would hunt ? Also, it has always idled at 760-800rpm, its ever so slight, but you can feel it going up and down in those 40 revolutions, vagcom values show these numbers. Is this normal? Vagcom shows no codes. Thnks in advance.