1998 Blazer Random Misfire P0300 - Multiple O2 Sensor & Lean Codes, Fuel Pressure Diagnosis Needed
I have a 1998 Chevrolet Blazer experiencing random misfiring, especially when driving uphill—noticeably losing power. The vehicle has triggered a check engine light with code P0300 (Random Misfire). I've already had my mechanic inspect the spark plug wires and replaced the coil pack, but the issue persists. Additionally, the car is now showing multiple diagnostic trouble codes: Bank 1 System Lean, Bank 2 System Lean, and O2 sensor faults. I'm concerned about potential fuel delivery issues given the lean conditions across both banks. I've checked spark plug appearance—dry and tan—which suggests proper ignition—but the misfire continues. My mechanic is experienced (76 years old), but I'm now expecting a baby and need reliable, actionable advice before further repairs. Could this be related to low fuel pressure? I'd like guidance on how to test fuel pressure: turn off the key, observe pressure drop, and confirm it stays stable. A fuel pressure gauge can often be borrowed from auto parts stores. If fuel pressure is low, that may explain both the misfire and lean conditions. Any insights or troubleshooting steps for a 1998 Blazer with P0300 and multiple O2 sensor/lean codes would be greatly appreciated.
I'm assuming this is a 4.3L engine? Please post all relevant diagnostic codes—P0171 and P0174 are common in such cases. Initial troubleshooting steps: - Check fuel pressure; turn off the key and monitor for drop. Let me know your results. - Consider a fuel pressure gauge (available on loan at most auto parts stores). - Verify spark presence at all plugs—look for dry, tan color, which indicates normal combustion. My best guess is a fuel delivery issue causing lean conditions across both banks. I recommend addressing fuel pressure first before moving to other checks. P.S. GPA? Does that stand for Grandpa or General Performance Advisor?