I just got an 89 Thunderbird SC 3.8L it starts fine in the morning but I have to keep my foot on the gas till it warms up, after that it runs like new, sometimes it idles high and don't want to idle down, if I cut the engine off it will not start again till it's cool down again like a cold start. When it idles high I unplug the air flow sensor and it idles fine, when I plug it back in it idles high again........please help