97 Ford 4x4 F150 auto with 4.6 Lariat. Truck appears to run OK cold. After warming up the idle is rough and wants to stall. The truck has 69,000 miles. Sits in the garage alot. Original plugs and wires. I checked the IAC and it looks clean. I believe the IAC is OK due to the fact when the RPM at idle starts to die all of of suddent the rpm will pick up in an attempt to keep the truck running.BTW no CEL. My question is would an open EGR valve cause this problem ? No other problems other than IDLE after warming up. Just happened all of a sudden.