1997 Grand Marquis idle issue
 

My car wasn't starting in the morning unless I pressed the gas pedal and held it for 5+ minutes. Watched a video about tapping on the IAC valve. It worked for my car for about 2 weeks and I changed the IAC to an oem with new gasket. It helped it alot, it will now start and idle perfectly until I drive it and sit at a red light. It idles down to a stop and holds a nice idle for about 10 to 20 seconds and then it bogs down like it wants to stall. So I put it in neutral rev it and it seems to clear up till the next light and it does same thing. Before I changed the IAC it never had an issue at lights only starting Any ideas or information would be appreciated greatly.

I don't know if you solved this in the last few weeks. Did you clean the bore which the IAC resides? Carbon builds up on the pintle and in the hole where the pintle inserts. The carbon will either block air or cause the pintle to hang up in there. Try cleaning with a small toothbrush and some throttle body cleaner.