Specific symptoms: 2008 BMW 525Li (E60) hot car idle jitter (pleasure car), engine and accompanied by a sharp whistle, cold car is normal, engine hot car idle speed about 650rpm, when the speed is 850rpm-1000 rpm, jitter is useless, whistle is still the same.
Fault diagnosis: because a bottle of 3M carbon removal gasoline additive and 200 yuan of oil were added the day before the fault (at first, I thought it was caused by less gasoline, the proportion was too strong, and when I drove again, I went to add 200 yuan of oil to dilute it. The fault will still occur). Due to the maintenance of the car in Tuhu in the afternoon of the fault, the project changed the oil, machine filter, air filter. Air conditioner filter and gearbox oil and oil pan, go to Tuhu store to find out if it has anything to do with maintenance. When the store manager heard the whistle, he said that the exhaust valve on the valve cover was blocked, and it was with the valve cover assembly. I’m going to change it together. Then plugged in the computer to read the fault code, there is a fault record, did not say much. That is to say, maybe the oil was not good before and it was blocked, which has nothing to do with this maintenance. I’m leaving. Then call my friend who is doing maintenance and check his shop to see if there is a vacuum tube leak computer read the code again, did not find the leak place, so the fault code record is the intake vanos mechanism and exhaust vanos mechanism, and then the nose directly in front of the two vanos solenoid valve removed to clean, and idle test drive for more than 20 minutes, the fault did not appear, said to shake again to change the solenoid valve. I checked out and drove away. I just went out after a red light and began to shake again, similar to the lack of a cylinder. 4s is defined as a tourist car. As it was getting dark, I drove home.
After a few days have time, the car to the Miaojiang Road BMW 4s to do a test, detected that there are three external faults: 1, valve cover replacement assembly and check the vanos intake mechanical part. 2. Replace the intake and exhaust vanos solenoid valve (fault code 2A82 and 2A87). 3, abnormal noise of generator belt tension pulley (this is recommended replacement, this problem I found before, but has nothing to do with the current jitter fault). After taking a look, it costs more than 8,000, dripping blood. I paid the test fee and went home. Because I need to find a bigger 4s test to confirm it.
The next day, I went to the store of Fande Shanghai South Road to continue to test. This time, the first two fault diagnosis results are the same. There is an electronic thermostat fault, which is not directly affected by jitter and is ignored for the time being. It’s still too expensive. Pay the test fee and leave.
Through 4 tests and fault diagnosis, the first two tests can be used for reference, but the master also came out in 4s and has a lot of experience. The latter two 4s tests are very authoritative, so I bought a solenoid valve and a valve cover assembly to replace the test drive through a friend. After installation, I tested the car for a few days, and the two faults never appeared again and were troubleshooting.
Conclusion: after two 4s diagnoses, I also collected fault diagnosis cases on the Internet, one of which was very close. I read the data stream before changing parts (my own data will be sent out later). When the idle speed is normal, the data flow of intake camshaft position and exhaust camshaft position is transferred, and the data position and adjustment position are in line with the standard. However, during the test run, the position and adjustment angle of the intake camshaft do not conform to the idle speed value of the hot car. In fact, in addition to empirical judgment, it is very important to read the data stream when judging the fault.