1996 GMC Sierra SLE 5.7L Vortec: P0102, P0141, P0172, P0175 - Rich Running, Backfiring & Rear Brake Pop

Start by addressing the rich fuel condition—perform a fuel pressure check under KOEO (Key On, Engine Off) to observe any drop in pressure. A failing fuel injection spider assembly could be the culprit, as these components are known to fail and cause inconsistent fuel delivery. For the MAF sensor: inspect for vacuum leaks downstream of the MAF. Use the traditional spray bottle test with aerosol (non-oiled) to detect leaks—avoid using an oiled air filter, as it can interfere with readings. Next, evaluate the oxygen sensors. Focus on the post-catalyst O2 sensor, which has a heater circuit; these are typically checked after fuel-related issues have been ruled out. Note: The rear brakes popping when releasing the brake pedal is unrelated to engine codes and may indicate worn drum brakes or mechanical failure. It's advisable to remove the rear drums and inspect brake components, especially given the vehicle’s age and unknown service history.