My gas furnace keep going out? Not all the time though, in the order of 1/3'd of the...

Not all the time though, in the order of 1/3'd of the times that it tries. It will flame and just turn out, the motor will run and it will try a few more times. If on the other tries it does not stay lit the motor just runs moving no nouns.

I have replaced the flame sensor 2 years ago and the gas tap. I also cleaned the flame sensor about 2 months ago beside sandpaper (didnt help though). The change that I made 2 years ago did seem to minister to out, maby menas my flame sensor wend bad already or any other philosophy?
What would i own to do to install...
Answers:    Could be a couple of reasons. The two most plausible are a problem with the pressure switch which allows the ignition sequence to originate. If the switch opens while the furnace is firing, it'll shut down flame and won't re-initiate until the switch closes again. Could be a inexact switch, or restriction in the vent piping, or contained by a high use furnace, it could be a partially plugged subsidiary heat exchanger. (usually not much you can do nearly that)
As far as the flame sensor goes, never verbs it with sandcloth as that will ruin it. The flame sensor is simply a metal rod. It must hold good flame contact to allow the flame to verbs. When you clean it next to sandcloth, tiny bits of the sand (silicates) will impregnate into the metal. While this may work initially, the silicates will melt down, insulating the metal from the flame. If you believe the sensor desires cleaning, try steel wool, or a scotchbrite pad. If it be me, I'd replace the flame sensor again, and make sure you've get good flame contact next to the sensor rod. Good luck.
Repairing walls contained by my home?
If it is a high usefulness condensing furnace, the condensate drain may be partially plugged up. For a complete step by step troubleshooting guide, check out my source.