I have been having problems for 2 winters now and its getting worse. My igniter starts then the flame will start then you will hear clicks coming from the gas valve. While the clicks are happening the flame will attempt to go out. Once the flame goes out the process will repeat several times. If the furnace is not successful then only the motor below the impellor will run for hours and my house will drop in temperature.
I will turn the furnace off at the switch then back on and the furnace will work fine for many hours to several days then the problem will start again. I have cleaned eveything on the burner and replaced the sensor, module-ign (twice)
I am short on funds and cannot get a new furnace and I have read about the heat exchange and that part alone is $950.00 could it be something simple or something I missed

Have you found anything out I'm going through the same thing now