2004 Ford Freestar missing Possible fuel pump?

My 2004 Ford Freestar check engine light was on and running really rough. I got my spark plugs and wires all changed. Car did good for about 5 days. It's missing again but no engine light is on. Seems to do this when it's raining. Put heat in the tank also. Don't know why it's missing. The gas was on low and I am wondering if it's the fuel pump. I had the filter changed with the tune up also. How do you know your fuel pump is going bad?

You have to get a pressure check to make sure the right pressure is pushing gas to the motor,and check for any leaks where air might be pulled into the line,which would cause a stuttering engine.

if you have a bad spark plug wire, it will draw condensation and make engine run rough.... you can check this by getting a spray bottle and filling it with water, spray a mist over top of the wires while the car is running, and if one is bad it will show.... (looks like little lightning coming off of wire) .... hope this helps.