I'm thinking IAC

[Canuckcleaner]

Well.....the last two times I've started the stang it has taken almost 5 minutes of keeping it above 1000rpm before suddenly it will hold itself at an idle. Now some more info, the first time the car sat for over a month and today the car had sat for 2 months. Both times it's acted the same. It's almost like the idle won't hold its own until it starts to get warm.

Any other suggestions cause I'm going to order an IAC if nobody has any other suggestions.

[Ponyryd]

What are we working on? Iac maybe but it could easily be something else.

[Ghost Rider]

I've had trouble with the IAC in my mach...getting gunked up...but in my experience...the problem doesn't go away when the car warms up...it acts up whether it's cold or hot...

so like mentioned abobe it could be something else

however...pop it off, give it a good cleaning and put it back on...you'll know pretty quick

I sprayed mine out with TB cleaner...worked like a charm after that

[Canuckcleaner]

Sorry should have mentioned that. 2000 GT 5speed.

[Ponyryd]

Have an oiled-air filter?

[ZR]

Plugs recent?
MAF cleaned recently?
Tested coolant temp sensor?
Clean IAC regardless.

[Canuckcleaner]

Plugs - nope haven't touched em
Maf- cleaned back in the summer. Have put 500 on it since then.
coolant sensor- nope that's new one. Where and how Rick?
IAC - WILL do

[ZR]

When it's been sitting, was the battery hooked up or disconnected?
Before touching anything else, as suggested above, clean IAC first. If it improves your good, if it only improves for a short time, replace IAC.
Keep in mind, before jumping to conclusions on a specific cause, should always do, fresh / in good shape plugs, fresh fuel filter, clean air filter, clean MAF, clean IAC, check all air intake connections for leaks, especially after the MAF, check vac lines, retest. May also include checking fuel pressure from a cold start. On a non return style fuel system, if the check valve in the pump is weak, can allow fuel to drain back which can result in excessive cranking when cold followed up by runs rough / poor idle until all air is purged via the injectors. Seeing a good number of pump failures in '99 up GT's, most times it results in either an erratic or no start cold condition though.
The 4.6's of all years are also somewhat intake gasket prone. Can be gaskets failing or a combination of aluminum corrosion actually pushing the intake up and off the gasket itself.

[Canuckcleaner]

OK Thanks Rick. I'll go at it here in a few weeks

[DS]

I've got a 2000 gt 5-speed as well and have had the exact same problem. Do you drive short distances? If so, there will most likely be carbon build up as the IAC won't have time to clean itself like it would on a longer drive. I had to keep removing it and cleaning it out with a Q-tip and some throttle body cleaner every 4-6 months.