P0452 and P0306 Codes in 2001 Chevrolet Silverado 4.3L V6: EVAP System & Cylinder 6 Misfire Diagnosis
I own a 2001 Chevrolet Silverado Base with a 4.3L V6 engine, currently at 230,000 miles. I've been experiencing a persistent P0452 code (EVAP system low fuel tank pressure) for months. I've already replaced the gas cap, but the issue remains. The code appears only when I start the truck and disappears if I erase it before driving—reappearing upon restarting. In addition to P045 or EVAP-related issues, I occasionally experience a flashing 'Check Engine' light during aggressive acceleration (which I don't perform frequently), followed by a P0306 code indicating a misfire on cylinder 6. The warning light stops flashing when the engine returns to steady-state operation. I've replaced spark plugs, ignition wires, distributor cap, and rotor—yet the P0306 issue persists, though the truck runs smoothly under normal conditions. I also have concerns about low oil pressure, which has been noted by mechanics. They suggest replacing main bearings, but given the vehicle's age, I'm unsure whether this repair is cost-effective. Any insights into what might be causing both the P0452 and P0306 codes? Is there a connection between EVAP system performance and cylinder misfires?
P0452 is not related to fuel pressure—it's an EVAP (Evaporative Emission Control) system code indicating low fuel tank pressure during leak detection. The flashing P0306 and misfire on cylinder 6 should be investigated for a faulty or clogged fuel injector, possibly due to internal leakage or restricted flow. As a temporary measure, try adding a can of Seafoam or Techron fuel treatment to help clean injectors. Additionally, use a mechanical oil pressure gauge to verify whether your current oil pressure readings are accurate and not misleading.