Failure phenomenon: a 2008 annual output of FAW – Volkswagen Magotan 1.8TSI car, equipped with 09G-6 automatic transmission, mileage 14000 km. Users complained that after starting the car, the engine has a short-term shake violently, Dayton car driving, fuel consumption display high.
check analysis: the car in the other service stations repaired, but failed to troubleshooting. Take the car, maintenance personnel with VAS5052A fault diagnostic detection, the gateway list engine failure information: 00010 P000A 000mdash; mdash; intake camshaft adjustment is too slow, sporadic fault. After clearing the fault code, and place the vehicle 20 min test, fault codes again. After the start of the vehicle 70 s, the engine shake vigorously (flame almost) normal about 7 s. Road test, the engine speed is raised to the 3 000 r / min deceleration when the speed drops 1 000 ~ 2 000 r / min, a clear Dayton car phenomenon. Observed during the deceleration of the vehicle fuel consumption, compared with the other cars, significantly higher. This is entirely consistent with the user reflect.
FIG 1
repeatedly test found that in case of engine shake, hear relays start working. Find the relay, and identified as the coolant circulation pump relay. It has to do with shake it? After it was pulled out the test, fault unchanged. Other test vehicle, is also found that the pull-in relay after starting the engine 70 s, thus excluding the doubt. Prompted by the fault code, try to replace the camshaft adjustment mechanism, but the fault persists.
FIG. 2
that the communication with the user, the failure is maintained after an oil change at 3 000 km. Just start the car engine shake cool, hot car normal, the other service stations into the current situation after maintenance. Then change the oil and fault what does it matter? Camshaft oil pressure adjusting mechanism is driven, so to focus on checking the oil circuit. Since magotan car oil filter is mounted vertically downward (FIG. 2), it is believed there is foreign matter falling when replacing the oil passage, resulting in reduced oil flow. Remove the oil filter seat, check the oil passage leading to the cylinder block and cylinder head leading to one-wayValve, no foreign matter was found. Remove the oil pressure switch, connected to the oil pressure gauge measuring the oil pressure, oil pressure at idle is 120 ~ 160 kPa, when 2 000 r / min the oil pressure is 270 ~ 450 kPa, are within the normal range.
Figure 3
Figure 4
To further fault diagnosis, we have to look at the relevant system works. Magotan engine by changing the position of the intake camshaft is changed intake phase, a phase variation in the range of 60deg ;. When the intake camshaft engine stalled at the most retarded phase by the lock pin lock. When the oil pressure exceeds 50 kPa, the lock pin is unlocked, controlled by the engine intake phase the control unit. When starting the engine, the intake phase lag to a maximum, in order to facilitate starting. When idling, the intake phase lag 34deg ;, smooth operation of the engine. At part load and hard acceleration, early intake phase, in order to increase the engine output torque. At full load, the intake phase lag to increase the engine output. The engine control unit by processing the signals of the engine speed, the camshaft position signal, temperature signal and the load signal, etc., to obtain the target phase and the phase control to follow the target actual camshaft phase adjusting mechanism. Camshaft adjusting mechanism (FIG. 3), cam shaft driven by the camshaft adjustment vane, the vane sides for the advance chamber and the retard chamber, the two chambers by changing the pressure, can change the position of the blade, thereby changing the intake camshaft i.e., change the position of the intake phase. Pressure in advance chamber and the retard chamber (FIG. 4) is controlled by a valve channel 4/3. An intake camshaft timing adjustment valve N205 promote central valve passage 4/3 displacement valve, thereby changing the pressure in advance chamber and the retard chamber (FIG. 5). N205 by the engine control unit outputs a duty ratio control signal, the duty cycle hours, the armature is retracted, the central valve 4/3-port valve is spring driven to the left, the lag increases chamber pressure, chamber pressure is reduced in advance, the blade lag the direction of rotation, the intake phase lag. When a large duty ratio, the top of the armature, right central valve 4/3-port valve, the pressure increase advance chamber, the chamber pressure is reduced hysteresis, the rotor blade to the advancing direction, the intake phase is advanced.
Figure 5
Figure 6
Figure 7
, a fault with the USB computer cable car engine 091 sets of data stream (FIG. 6), compared with the normal data flow set vehicle engine 091 (FIG. 7), found in the positions indicated in FIG significantly different. No. 1, an engine control unit additionally output a phase adjustment command. It is this instructions cause the engine speed to 400 r / min, and a sustained severe jitter of 7 s. In this process, no change of target phase, which is the engine control unit described specific response to a failure. No. 2, a phase delay adjustment process, the actual rate of change of phase is less than the target rate of change of phase. Phase lag adjustment is too slow to keep up with changes in the target phase. It is seen from Figure 6, when the phase adjustment is completed, the actual phase after 10 s later than the target phase, which is expressed in engine failure fault code is the same. Then find the cause of a phase lag adjustment is too slow reason, has become the key to solve the problem.
Figure 8
10
I assume throttling phenomenon oil path, because the system working pressure is normal, only the actual flow is below the design flow, will lead to the phase adjustment is too slow. Check the focus so the hydraulic line, the first figure corresponding relationship between the oil passage (FIG. 8), but has not identified the problem. But found abnormal, 4/3-port valve and a solenoid valve N205 contact traces (FIG. 9) in the inspection channel 4/3 valve. If no gap (10) therebetween, the solenoid valve in a case where the work has not been N205, central valve 4/3-port valve has been pushed, the oil passage almost closed hysteresis adjustment, at a time when the opening of the oil passage degree should be the maximum. This confirms the assumption that the beginning of the oil path does exist throttle phenomenon. Normally, 4/3-port valve and a solenoid valve N205 should leave a certain clearance, to ensure the correct degree of opening of the oil passage (FIG. 11).
See fitting relation (FIG. 12), a gap was found with 4/3 solenoid valve passage N205 by the sealing ring 4 is determined. Fixing bolt 1Standard tightening torque 9 N · m, if the torque is too large it will deform the sealing ring 4, so that even N205 mounting plane deformation, resulting in the 4/3 solenoid valve passage N205 assembly gap disappears.
11
12
Solution: replace the sealing ring 4, the correction N205 mounting plane, a bolt tightening torque according to the standard. Test observation, fault completely ruled out.
reviewed: This fault genus human error. Start may be due to the addition of low-quality fuel, causing the engine to cool a serious car shake. Since the unstable oil pressure, the engine control unit determines the adjustment mechanism to the camshaft occasional failures. Maintenance staff found fault codes, disassemble and clean the camshaft adjustment mechanism directly, but there is no bolt tightening torque according to the standard installation, resulting in failure of the present generation. Seen by the present case, in the fault diagnosis, fault code to be used together in conjunction with the data stream, so that more accurate analysis of failure mechanisms, find the point of failure. In addition we must operate in strict accordance with the standards of maintenance manuals during maintenance, human error or due to the improper operation generated is often difficult to find.
(An Wentao)