Truck Sputtering and stalling when warm

Hello, I’m Pete from the Car Genius team at RepairPal. I’m sorry you’re dealing with this concern on your 2003 Chevrolet 2500 HD. With the concern you have above the sputtering and stalling on this model in some cases can commonly be caused by carbon build up inside the throttle body itself or the upper intake/plenum gaskets leaking allowing excess air into the engine. These were very common. I recommend having the throttle body checked for carbon build up and if carbon build up is found it will need to be cleaned to correct this concern. If the throttle body itself is found to be o.k. then I recommend having the engine checked for any vacuum leaks, the intake itself had a gasket design that was common to fail and required replacement with the updated version seals/gaskets to resolve this concern. If these have already been checked into and found to be o.k. I recommend having your fuel system checked to see if there is a loss of fuel pressure as it can also be common for the fuel pump itself to start failing to where it causes a loss of fuel pressure. In many cases these tests/inspections can be best to have performed by a certified shop as some of the testing may require special tools or equipment. If you’d like to find a trusted, certified repair shop in your area, you can check here: https://repairpal.com/certified. If you need more advice, or have any further questions about your vehicle, we’re here to help. Just give us a call at 877-913-1554 where we will be happy to assist!