EXPO 95, which had not been driven for one week, can not be started. The bettery is rechared. The starter is running. Checked the spark plug by connecting it to the bettery ground. There was no spark. Here is Chicago. It is cold recently. Recently I noticed the engine's power was not strong enough just after the engine started. I had to drive the car for a while before the engine's power backed to normal.
What could be wrong?

Well, if there's no spark, you might want to start with some new plugs. :thumbsup:

I left the old plug in the engine and connected the wire to a new plug which was well grounded.