2001 Hyundai Elantra rough idle/ glowing exhaust

Car starts great and idles fine for about five minutes, then runs eratic and exhaust glows red. Removed exhaust pipe from exhaust manifold and tested again as I supected catalyc converter. Still have same problem with exhaust disconnected less glowing. Engine has about 60,000 miles, replaced just 2,000 miles ago. Body has 128,000. Car ran very well the first few weeks I have owned it. I have checked the cooling gauge and it appears to be at a normal range. Has new water pump and t-stat, belts and I have only let run maybe 10 minutes before shutting off, noticed no cooling fans run, but not over heating. Check engine light is on