I have a 94 thunderbird 3.8L. This is what it does. When i start it, it idles wonderfully. But as soon as i put the vehicle in reverse it shakes and stalls. When i put it in drive it's fine again but the first time i stop it idles rough and continues to every time i stop throughout my trip. Occasionally it will stall as well. i just replaced the MAF sensor because i had had trouble with it before. Does anyone know how to check this sensor to make sure i got a good one? Like how many hertz it should be running at or something scientific like that? Or any other ideas what could be causing this behavior. Thanks. Also my check engine light is on. Codes are 157, 181, 189. oh, i also heard that sometimes when you put a new maf senor in it needs to relearn it to work properly. Is there a procedure for this because it's been about two weeks since i put it in. Any info is much appreciated. Thanks.