1991 Metro Idles Rough for about 5 seconds

Hi all,

I have a 91 Metro, its a good running car, I have noticed that I can crank the car when its cold, hot, after running the car or not, it will idle really really rough for about 5 seconds, then it clears up and runs great. It doesnt have any problems cranking or starting, after it hits it is going to idle rough. I can give it some gas and it immediately clears up, if I dont hit the gas it takes it about 5 seconds. Please let me know if anyone has any idea what the problem is.

Thanks

Could be a lot of things..................

Due for plugs, wires, cap, rotor.
Fuel pressure due to dirty filter.
Oil in cylinders (does it smoke on startup?)