First startup in the morning or if it's been sitting for hours my 99 Jeep Cherokee Sport won't stay running unless you have your foot on the gas. It usually takes a minute or two with your foot on the gas a little until it stays running. The check engine light isn't on, in fact the MIL bulb is working and even through 195,000 miles it's never come on. The tune-up has only got about 10,000 miles on it, using all Mopar parts and OEM plugs. I replaced the idle air control valve once, thought I got a bad one, and replaced it again and recleaned the port out and it still does it. I even cleaned the throttle body out and it wasn't all that bad. I replaced the PCV elbow with a new one. I checked for vacuum leaks all over the intake, throttle body, intake hose, vacuum hoses, and even valve cover grommets and didn't find anything. Any ideas on what it could be? Anything I could check here at home before I take it to the shop?