I have a 2001 Tribute and it will die when idling unless I keep it revved. Also, this problem occurs mainly when it's cold and as it warms up it will run fine. It surges and the lights on the dash board will dim. I've had this problem for over a year now and we've replaced the IAC, MAF sensor and spark plugs not to mention many of the coils. Does anyone have suggestions on what to do next?