I have a high efficiency Luxaire furnace. It is at least 5 years old since we bought the house. It has a glow bar. The bar gets hot. THe gas comes in. It lights. Burns for about 3-5 seconds then goes out. When it goes out I hear a small swoosh like air is being released somewhere. Then the cycle starts over. The furnace was not used at all last year because we burned wood all winter. I had new ducts and lines run.

It has 2" PVC exhaust and intake lines.

What could be the issue?

I had a similar issue before and it was a bad sensor.

I tried cleaning the flame sensor but still same issue.

Make sure intake and exhaust pipes are clear. Since they weren't used last year there may be a wasp nest or other blockage.