2004 Honda Civic, automatic

I'm having an issue with my ck engine light coming on for a day and then going out. I've gone to Auto Zone twice to get the codes and have gotten two different answers to my problem. Here's the problem:

When the check engine light is on I have issues with a hard down shift when slowing down to a stop. When increasing speed I have problems with it going into the next gear. I usually have to give it more gas for it to work.

First time I had the codes checked Auto Zone said it could be the TP Sensor. Second time they said it probably was the Purge Solenoid.

Funny thing is when the ck engine light is not on, the car operates just fine. This morning it was okay, but by the time I was ready to travel home the light was on.

Any clues? I appreciate any and all responses to my problem.