Buick unstable operation

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Symptom: one using pressure-type (ie, D-type) petrol injection engine Buick sedans, arising from the use idling is not smooth, with weakness, exhaust pipe blasting and so on. After turning the car fault self-diagnosis system, fault light alarm; using the code detector detected the fault code is "33" (MAP pressure sensor fault code) and "45" (oxygen sensor fault code).        Failure to check: initially suspected MAP pressure sensor and oxygen sensor failure. Because the former is mainly based on pressure-type fuel injection system into the gas and combustible gas mixture prepared; while the latter fails, the combustion exhaust pipe can not be detected correctly and thus unable feedback correction fuel injection quantity of the correct information for the computer . But after the pressure sensor MAP and oxygen sensor replacement, the fault persists. With a vacuum gauge to measure intake manifold vacuum, and its value is only 30 kPa, and volatility. By measuring cylinder pressure cylinder, two cylinder pressure is only 0.2 MPa, but also volatility. Add a little oil and then measured unchanged changed. Pressure ranges for each cylinder in the cylinder itself, not the interruption in all the cylinders can be controlled i.e. the intake pressure sensor control device. Further examination, and finally found intake and exhaust valve leakage.       Troubleshooting: After thoroughly cleaning the lower pressure behind two cylinders of liquid column, the fault that is excluded.       Failure Analysis: As the liquid column behind closed doors with oil mixed exhaust lax, leading to intake manifold vacuum ?PX value is too low is the root of the formation of this failure, and MAP pressure sensor fault code and oxygen sensor fault code is this a failure of representation. http://www.diyobd2.fr/wholesale/wifi-elm327-wireless-obd2-auto-scanner-adapter-scan-tool-for-iphone-ipad-ipod-1816.html