Can someone help me with this?

On cold mornings, the engine misses.  If I drive before it gets warm it lugs
and I can even hear what sounds like a backfire.  It idles at about 1300
rpms, then returns to normal after warmup.

At other times, while waiting for it to warm, the idle will drop to 500 or
so until I give it gas, else it might die.

Any input would be appreciated.

Thanks.