Jenn Air Gas oven doesn't fully heat

Larger oven doesn’t come up to temperature. The smaller left oven works fine, and the broiler in the large oven works ok as well. The ignitor will glow and ignite the burner, but I get a sputtering sound coming from the gas jet/port in the front that feeds the burner. This comes and goes, and when that happens the burner flames aren’t as strong. Even when it doesn’t sputter it still doesn’t heat like it used to. Not sure if it’s the spark ignitor or a bad or clogged port. Thanks for any help!