I noticed when I have a cold start in the morning it idles rough for a short time and then seems to be fine. But, after not running it for a couple of days, it was worse. Rough idle and missing for a bit before it finally came right. This only happens on a cold start. Once its running and warm there is no problem for the rest of the day. There are a few suggestions for a car when it does this, like faulty ECT sensor (water temp),fuel injectors, fuel pressure valve etc. I am leaning towards the ECT valve, $40 or so. I do remember my old Audi doing something the same some years ago but can't remember what the fix was? Does anyone else have a suggestion or had similar problems?
