Heat will not work properly when car is not moving

Hello-

Here I am again-with a different problem. The other I perviously posted is still bad, but this is also concerning me.

First of all-had the cat replaced and tune up done, etc. Car was missing really badly prior to the tune up and replacement. SES light was NOT on though.

I get the car back-SES light goes on, shady mechanic says "not to worry-it's an emissions code." Says something about Bank 1, sensor 1. But did not give me exact code-am going there tonight to get code and get cleared as well as oil change.

Now however, when I turned the heat a few days ago, it was not warm at all when I was not moving. As long as the car was going-it stayed warm, but once I stopped, it would get cool.

I had absolutely not a problem with this car for 2 years until the car started missing, about 3 months ago. It got to the point where I had to get it fixed, which I THOUGHT I did.

If anyone has any advice, tips, etc for me I would greatly appreciate it.

And I will get back Monday w/the actual code to see if any of you wise folks can help a girl out here.

Thanks!

Try replacing the thermostat. Could be an easy fix. Otherwise I would say maybe the heater core is going bad.