hi i took my car to a mechanic because every once in a while when i start it in the morning after it rains or is colder it idles low n stalls out unless i keep my foot on the gas until it warms up for 2 or 3 minutes he replaced the oxgen censor it was fine fine for 5 days n yesterday i went to work it started fine but when i left it did again it wasnt cold but it had been raining any idea what it could be