2003 TB EXT 4.2l is throwing code P0171 after driving for about 20 minutes at speeds of 55-70. The vehicle has almost 160K miles on it, with a remanufactured engine that only has 20K miles on it. Over the past 3 months this is what has happened.
I was getting a code P0340 (Camshaft position sensor circuit malfunction). I replaced the sensor and a bad ground wire from the sensor to the PCM, which solved the problem.
Shortly after I had a misfire on #2 cylinder P0302. No spark, replaced coil pack. Code gone.
Next I got a lean code P0171, along with a multiple misfire code P0300. Also had P0128 engine temp too low. I had a slight leak on the valve cover, above the VVT actuator solenoid, so I pulled the generator, PCM, intake manifold, valve cover, fuel rail, and cooling fan off. Checked the timing chain and made sure it was still tensioned and on the cam gear marks, removed and cleaned fuel injectors, installed new gasket on throttle body, valve cover, and intake. Cleaned the air temp sensor, throttle body, resonator, and intake manifold. While I had it torn apart, I also had the generator tested, and I rebuilt the starter.
For the engine temp too low P0128. I checked the ECT sensor and thermostat, and replaced the thermostat, which solved the temperature problem. Fuel pressure at 56psi, and only drod ps to 54psi after 30 minutes. Fuel pump and fuel filter only have about 7000 miles. Battery at 12.7 volts.
While I was at it; I also replaced the MAP sensor, tested and replaced VVT actuator solenoid, Fuel pressure regulator, the vacuum hose going into the passenger side of the intake manifold, new iridium spark plugs, plus Oil and filter.
After driving it for a while, with engine hot, now I'm back to the P0171 code only. Fast startup with engine cold or hot, slight stumble while at idle, but no misfire codes. Idle is back up to 800-900 RPMs from normal 600 RPMs when engine is warm. Everything points to a vacuum leak, but I've listened, pulled hoses and plugged holes, sprayed carb cleaner everywhere with no change (brake booster, booster hose to intake manifold, PCV hose, valve cover vent hose, air intake, air filter hose to resonator, resonator to throttle body. I loosened the exhaust between the manifold and the catalytic converter, and no change in engine performance.
The upstream O2 sensor has power to the signal side and the heater side, and has continuity. Only ohm'd the heater side of the downstream sensor, and it was good.
I live in the country, and don't have a scope.
Any ideas? Will a small leak in the valve cover gasket possibly cause a lean condition? Is it likely an O2 sensor?
I was getting a code P0340 (Camshaft position sensor circuit malfunction). I replaced the sensor and a bad ground wire from the sensor to the PCM, which solved the problem.
Shortly after I had a misfire on #2 cylinder P0302. No spark, replaced coil pack. Code gone.
Next I got a lean code P0171, along with a multiple misfire code P0300. Also had P0128 engine temp too low. I had a slight leak on the valve cover, above the VVT actuator solenoid, so I pulled the generator, PCM, intake manifold, valve cover, fuel rail, and cooling fan off. Checked the timing chain and made sure it was still tensioned and on the cam gear marks, removed and cleaned fuel injectors, installed new gasket on throttle body, valve cover, and intake. Cleaned the air temp sensor, throttle body, resonator, and intake manifold. While I had it torn apart, I also had the generator tested, and I rebuilt the starter.
For the engine temp too low P0128. I checked the ECT sensor and thermostat, and replaced the thermostat, which solved the temperature problem. Fuel pressure at 56psi, and only drod ps to 54psi after 30 minutes. Fuel pump and fuel filter only have about 7000 miles. Battery at 12.7 volts.
While I was at it; I also replaced the MAP sensor, tested and replaced VVT actuator solenoid, Fuel pressure regulator, the vacuum hose going into the passenger side of the intake manifold, new iridium spark plugs, plus Oil and filter.
After driving it for a while, with engine hot, now I'm back to the P0171 code only. Fast startup with engine cold or hot, slight stumble while at idle, but no misfire codes. Idle is back up to 800-900 RPMs from normal 600 RPMs when engine is warm. Everything points to a vacuum leak, but I've listened, pulled hoses and plugged holes, sprayed carb cleaner everywhere with no change (brake booster, booster hose to intake manifold, PCV hose, valve cover vent hose, air intake, air filter hose to resonator, resonator to throttle body. I loosened the exhaust between the manifold and the catalytic converter, and no change in engine performance.
The upstream O2 sensor has power to the signal side and the heater side, and has continuity. Only ohm'd the heater side of the downstream sensor, and it was good.
I live in the country, and don't have a scope.
Any ideas? Will a small leak in the valve cover gasket possibly cause a lean condition? Is it likely an O2 sensor?