2002 GMC Sierra is missing when it hasn't been ran for a few days?

[what_to_do?]

I have a 2002 GMC Sierra 1500 2wd that is missing when it hasn't been ran for a few days. We have replaced the spark plugs and wires. It has a newer distributor cap too. It will start fine and when you shift it into gear it will die after not running for several days. If you start it and keep the RPM's up it will not die but it will run rough (like its missing). It will come out of it if you drive it for a few miles. It will also run fine when you drive it everyday. Any ideas on what this could be?

 

[pedro7of9]

its "hasn't been run" .....[English major]
1 vacuum leak
2 look under dist cap anyway...some chevys eat up caps ,,
3 leaky injectors...dripping over a few days..flooding plugs...dry out when hot..

 

[MISTER TWO]

Ignition coils (also called coil pack, igniter).

There's three styles of ignition for this vehicle, unfortunately. The common igniter is the one most prone to dying. This is linked to in the SOURCES.

 

[dirocyn]

Let it sit for a couple of days, then check your spark plugs. I'm betting you find at least one plug is fouled with oil (leaking valve guide) or gas (leaking injector).