Rough Idle
 

I have a 1996 F150 5.8. 210,000 miles. It runs great except that after the engine has warmed up, shut down for 20 minutes, on restart, it runs rough for 30 seconds and then smooths out. It started about 10 years ago when the ambient temp was around 100 degs f. Each summer it seems to occur at a lower temp. No trouble codes.