Reply – The new LaCrosse trembling inability to accelerate the engine idling
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The new LaCrosse trembling inability to accelerate the engine idling
— by kobd2 kobd2

Symptom: a the 2011 Shanghai GM Buick LaCrosse sedan ( equipped with 2 .4 LLAF engine ) , the cumulative traveling about 40,000 krn. Driver to reflect the tachopro 2008 car two days ago when the highway feels weak acceleration , the engine sounds muffled , engine failure during normal driving and idling lights sometimes flicker. Then went to a service station for repair , diagnosis of injector failure , because of the service station without accessories , so he continued to travel more than 500 krn, but also found fault occurred since the emergence of the high fuel consumption of the car .

Troubleshooting : After receiving the car and found the car engine fault lights lit immortal, engine idle shake obvious. With fault detector test , autologic collect fault code has : P0300 eleven engine misfire ; P0303 eleven 3-cylinder engine misfire ; P0172 eleven high voltage adjust the fuel system . Read the data stream is then found that long-term fuel trim is -30 % , 3-cylinder misfire frequently found after the inspection .

Then based on the obtained three read fault codes and data flow analysis of vehicle malfunctions. From the 3-cylinder engine fire to fire frequently , volvo vida and to adjust the fuel system high voltage , combined with high fuel consumption , and engine shaking phenomena such speculation, should be 3 cylinder misfire frequent adverse work of the cylinder , the engine power down, that the focus should be on the impact of 3-cylinder misfire can be detected for each element . Measuring ignition coil resistance , normal ; observe spark plugs, basically normal, but to be sure , or will it be a replacement ; 3-cylinder cylinder pressure measurement , and each of the other cylinder is no big difference . Check the suspected point 3 cylinder injector is faulty. Detection of 3-cylinder injector resistance , in line with the requirements of maintenance data , in order to secure the trial after his replacement, engine working conditions improved slightly ; observation data stream , then the long-term fuel trim value is -5% , but in the engine after running about 5 min, the engine idle shake intensified. Until then view the data flow , long-term fuel trim value reached 25% , and 3-cylinder misfire again this time , but also with a small two -cylinder misfire phenomenon . This fault diagnosis , fault detector information provided has been helping us . So timely adjust their thinking , provide information from the data stream query again . After careful analysis, long-term fuel trim values ​​have been high , should also be excluded from the start mixture. So check the tightness of the intake system , check the vacuum hoses for cracks , distortions and connections ; then check the air filter or without fouling , clogging the intake manifold , throttle body or without blockage , the results of the inspection items were normal. Check the intake manifold absolute pressure sensor parameters camp , but also meet the requirements ( standard value of 19 kPa-42 kPa). Suspected injector leak , causing excessive gas mixture , but the injector was tested , and no failure. Finally, only the remaining crankcase through Phoenix and fuel evaporative emission control system is not checked . Then find along the crankcase ventilation hose leak , when checking the oil in the crankcase oil discovery , the upper limit oil level much higher than the predetermined (FIG. 1 ) , and the more dilute the oil , gasoline with a very strong smell ( crankshaft box oil level is high , icom bmw resulting in increased resistance to rotation of the crankshaft , the driver will be reflected in the sound muffled engine running phenomenon ) .