2002 Ford Taurus P1131, P0316, P0303, P0174 & P0171 Codes: Misfire, Lean Mixtures and Poor Acceleration Diagnosis
I'm experiencing multiple engine trouble codes on my 2002 Ford Taurus: P1131, P0316, P0303, P0174, and P0171. The check engine light flashes intermittently while driving instead of staying steady, and the car runs poorly with weak acceleration and delayed response. I believe these codes relate to an oxygen sensor issue, a misfire in cylinder 3, and lean air-fuel mixtures across both bank 1 and bank 2. As someone without formal mechanic training but experienced in DIY repairs, I'm looking for clear guidance on how to diagnose and fix this. I plan to start with replacing spark plugs—though I’m aware that cheap store-brand parts may not suffice—and inspect for vacuum leaks. I’m also unsure what 'system too lean' means technically. Any detailed explanations or step-by-step troubleshooting tips would be greatly appreciated.
Check fuel pressure and perform a fuel pressure leak-down test. Avoid using cheap spark plug brands—opt for quality OEM or high-performance parts. When removing the plugs, note their condition: wet, dry, black, or tan? Also inspect for vacuum leaks—these are common causes of misfires and lean conditions.