2001 Mercury Cougar idling high, IAC replaced
My son's 2001 Cougar is idling at around 3000
rpms when stopped, it will jump between high idle
and almost dying. When he puts it into park it will
die. When he comes to a stop (for instance, at a
stop sign) the car will lurch forward like it's trying
to go. He replaced the IAC valve and sensor. A
mechanic looked at it last week and said that when
he unplugs the sensor, it runs great, but will die
when you stop. He checked the car over and found
no vacuum leaks. He said it's like there is a
malfunction between the IAC and the computer,
but no codes come up. Does anyone have any idea
what this could be?