I am working on an '02 WRX w/ 60k miles. The car seems too lack power in mid-range RPM (3000-5000 RPM). It's also getting a trouble code of P0171 (bank 1 too lean). The factory shop manual has a troubleshooting checklist for that code which includes fuel pressure, MAP sensor, Idle Air Temp (IAT) sensor, and Coolant Temp (CT) sensor. I checked the fuel pressure with and without pressure regulator and the pressures are in the proper range (36 and 41 psi, resectively). The manifold pressures are within proper ranges with key on/engine off and at idle. IAT reading was about 5 deg above ambient (within spec). CT was exactly to spec when the engine is fully warmed-up. I also checked the following: air filter is clean, spark plugs are relatively new with no deposits, fuel filter is new, the front O2 sensor appears free of deposits, The blow-off valve has been replaced. I removed the intercooler and carefully checked hoses and intake tubes for vacuum (or pressure) leaks and found none. I read live sensor data while the engine was running using an OBD2 scanner and all relevent sensors hade readings that made sense (O2, MAF, IAT, MAP, TPS, etc). I am all out of ideas on this one. I would appreciate any suggestion of where to look next.
- posted
17 years ago