Q: have replaced fuel filter, air filter, pcv , cap & rotor, plugs Every once in on 1996 Chevrolet Suburban 1500

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
a while the engine backfires when starting. Checked OBDC and NO fault codes show up. After the backfire the engine will start and run rough for about 30 seconds and then clears up and runs fine. Mileage is approx 123000.
Backfire occurs on a cold start or a warm start.
Any help would be appreciated, Thank you
(2) Answers