Advanced Automotive Fault Diagnosis
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LÔØI NOÙI ÑAÀU, ledklok
- Điều hướng trang này:
- Engine rev/min sensitive
- Noise and vibration while turning
| to 50 mph)
with light acceleration, a moan- ing noise may be heard and possibly a vibra- tion is felt in the front floor pan. It may get worse at a certain engine speed or load. 2. Acceleration/deceleration with slow accel- eration and deceleration, a shake is sometimes noticed through the steering wheel seats, front floor pan, front door trim panels, etc. 3. High speed a vibration may be felt in the front floor pan or seats with no visible shake, but with an accompanying sound or rumble, buzz, hum, drone or booming noise. Coast with the clutch pedal down or gear lever in neutral and engine idling. If vibration is still evident, it may be related to wheels, tyres, front brake discs, wheel hubs or wheel bearings. 4. Engine rev/min sensitive a vibration may be felt whenever the engine reaches a particu- lar speed. It may disappear in neutral coasts. Operating the engine at the problem speed while the vehicle is stationary can duplicate 10 Advanced automotive fault diagnosis Diagnostic techniques 11 the vibration. It can be caused by any compon- ent, from the accessory drive belt to the clutch or torque converter, which turns at engine speed when the vehicle is stopped. 5. Noise and vibration while turning clicking, popping or grinding noises may be due to the following: damaged CV joint; loose front wheel half shaft joint boot clamps; another component contacting the half shaft; worn, damaged or incorrectly installed wheel bearing; damaged power train/drive train mounts. After a road test, it is often useful to do a simi- lar test on a lift. When carrying out the shake and vibration diagnosis or engine accessory vibra- tion diagnosis on a lift, observe the following precautions. ● If only one drive wheel is allowed to rotate, speed must be limited to 55 km/h (35 mph) indicated on the speedometer. This is because the actual wheel speed will be twice that indi- cated on the speedometer. ● The suspension should not be allowed to hang free. If a CV joint were run at a high angle, extra vibration as well as damage to the seals and joints could occur. Support the front suspension lower arm as far out-board as possible. This will ensure that the vehicle is at its correct ride height. The pro- cedure is outlined by the following steps. 1. Raise and support the vehicle. 2. Explore the speed range of interest using the road test checks as previously discussed. 3. Carry out a coast down (overrun) in neutral. If the vehicle is free of vibration when operating at a steady indicated speed and behaves very differently in drive and coast, a transmission concern is likely. Note, however, that a test on the lift may pro- duce different vibrations and noises than a road test because of the effect of the lift. It is not unusual to find a vibration on the lift that was not noticed during the road test. If the condition found on the road can be duplicated on the lift, carrying out experiments on the lift may save a great deal of time. tải về 7.07 Mb. Chia sẻ với bạn bè của bạn:
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