Thanks for the tips, I went to check the orifice and found that the wrong orifice was in the furnace and the pressure regulator was also wrong, the gas valve & orifice were setup for propane, So I switched it all around and all is workign as it should be, that is how is was when I bought it, see...

I have a Nordyne Intertherm Furnace, Model number M1MB 070A AW, the furnace locks out due to failed ignition, but it only does it very rarely but when it is burning the warning light is flashing for weak flame. I have checked the pipes and there is no blockage also the ignitor works, so it has air, ...