Hi sounds like you have a few issues. First thing with the misfires and o2 sensor control limits sounds like you have a air leak. Very common for the intake boot from air box to throttle gets torn or cracks right around the throttle area. Your o2 sensor fault for short to ground is usally a bad o2 sensor. Evap leak can be a bad gas cap. Or may have a leak somewhere else in the system which at the dealer we use a smoke machine to fill the evap system and look for leaks as that could be many things. Thanks mike
The problem starts just after a cold start, the first few seconds it idles fine, then there is a strong one or two cylinder miss (ro about 3 or 4 monits) and a little tapping (almost sound like backfire into the intake) in the engine compartment for a couple times. The tapping stops, the miss continues, after which the engine speeds up a little and then the idle becomes a little rough, but no distinct miss (as evident by no regular pulsing of exhaust out of the exhaust pipe. Shortly thereafter, the engine warms up and the car runs, accelates, and idles flawlessly until the next cold start.
Any more clues other than the intake manifold? I it is hard to imagine that the intake manifold or connectors heat up and stop a vacuum leak?
Actually, I just found the large elbow hose right before the throttle plate has a bad small elbow hose extension (small accordion style, very flexible). This hose is cracked and slitted (partially blown). It is about 1" in inside diameter. You have to replace the whole hose (big and small). Could this be the whole cuprit? I squeezed it a little and the idle changed and became erratic.
I am ordering a new hose.