The oven was taking forever to preheat, then did not get up to temp at all. Comments on the forum and repairmen said it was the ignitor, so I replaced it. The oven worked better, but still took too long to pre-heat. Now it does not reach temp at all again. The flame ingites but I noticed the size of the flame is much smaller than the flame in the lower oven, which works fine. Could the gas tubes be plugged. What can I do? I cannot afford a professional repairman.