A mileage of about
80,000 km, equipped with N55 engine 2010 BMW 535GT sedan. The car accelerated
irregularity.
Check and
analysis: Use special car diagnostic tool found the car at 80 km/h speeds, the engine speed 1 700 r/min, it seems to
be an invisible force pulling back. When the speed reaches 110 km/h, the engine
speed 1 800 r/min, the pull power disappears, but the body appears shake
violently. When the vehicle speed reaches 135 km/h, the engine speed 2 200
r/min, the vehicle was transferred to normal driving.
Use cruise control
function, set the speed at 110 km/h, the body shake persist. Changed the shift
mode of the transmission to sport mode, the engine speed is increased to 2 300
r/min, the body shake disappear.
Under the premise
of keep the speed as 110 km/h, take manual mode shift. When 8-speed 1 800 r/min
shaking appears, 7-speed 2 300 r/min shake weakened, 6-speed 2 600 r/min shake
completely disappeared.
Integrated test
results, found shaking occurred mainly at speeds 110 km/h, the engine speed 1
800 r/min. Analyzed this time engine working condition can be seen, since the
car driving produced the drag has risen to a certain extent, but the engine
speed is lower, so the actual load rate of the engine is larger.
In this case, the
engine torque response characteristic is poor, prone to stalling. Since the
drag unchanged, slightly increase the speed, the stall phenomenon disappear
immediately, that shows the engine intake system is good, the problem is mixed
gas combustion bad.
Observed the fuel
correction amount data when the car driving, normal, so suspected the fuel
quality has problem. Extracting the fuel sample to check, found the color is
abnormal, pungent odor, is low quality fuel oil.
Troubleshooting:
After replacing the fuel and clean the fuel supply system, remove the adaptive
value of fuel correction amount, use BMW ICOM diagnosis no fault code, test the car, confirmed
troubleshooting.
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