My furnace is about 9 years old and when I turn it on I do get a igniter and my gas valve opens but I only get one flame out of 5. My flame sensor is at the far end from the first flame so I believe it is shutting the furnace down.

One flame out of 5?? Are you talking about the flame runners/burner tubes?

Yes the tubes is what I meant to say, it looks like I have a lot of build up on the flat part of the tubes so I will try to clean them and see if that helps.

Need to clean the burners and flame sensor. Turn all power and gas to the system off first.

Take the burners out of the furnace and knock the crud out of them by tapping the big end lightly on the concrete Then wire brush all of the little flame openings. Install them back in the furnace and try it. Also that is a little flame tray at the very front of the burners make sure it is clean.