rough idle at startup

My sons 3.0 liter has a really rough idle when starting mainly in morning. Few hours later doesnt usually do it although when its rainy it is worse and does it more often.It always smoothens out after a few minutes. Recently put mass air on for different problem everything else is original, It is a 99 with 112000 miles. No service engine light just hate to start buying things.THANKS DAVE

My son has a 4l V6 with the same problem.
Rough idle at start up. Check Engine light on code misfire #4 cylinder.
I replaced plug leads PCV valve EGR valve and DPFE sensor.
I still have the problem.
I'd be grateful for some help here

U kno u can start ur own thread right

Have your power control module (PCM) checked. When you first start with the engine cold, your PCM is in a "default" mode, meaning it is operating on its internal input. As the engine warms up as sensed by the temeprature sensor, the PCM shifts to op mode which in effect runs based on the various external inputs such as O2, vacuum, positioning sensors, etc.