Troubleshooting of 2 Dongfeng Nissan Teana and Yida Sedan Faults

Case 1

Fault phenomenon: A 2008 Dongfeng Nissan Teana 2.0L sedan, equipped with an MR20 engine and an Xtronic CVT transmission. According to users, after the car has been driving for a long time in the city, if the shift lever is in D gear when waiting for a red light, a “gurgling” abnormal sound will appear at the rear of the car body (Figure 1).

Figure 1

Inspection and analysis: This fault has also been encountered in some franchise stores. After the vehicle has been driving for a long time in the city, due to the low-speed stop-and-go driving, the water produced by the engine combustion accumulates in the main muffler, causing the installation position of the main muffler to drop due to gravity, causing the rubber bracket pad to lose its buffering effect, and the working vibration of the engine drives the muffler to be directly transmitted to the car body through the bracket pad, resulting in abnormal noise.

Although the cause of the fault has been found, many repairs cannot completely solve the problem. After checking several faulty vehicles, the author found that there were obvious interference marks under the muffler bracket pad (Figure 2). According to the cause of the abnormal noise, the author believes that as long as the interference problem of the bracket pad is solved, the abnormal noise can be eliminated.

Figure 2

Figure 3

Troubleshooting: Use a blade to cut off the protruding part below the bracket pad (Figure 3), then reinstall the bracket pad and the main muffler, and confirm the troubleshooting through a period of follow-up visits.

Review and summary: Many new models usually have some faults at the beginning of their launch. Since the corresponding technical support and component improvement of the manufacturer need a process, in actual work, in order to reduce user complaints, maintenance personnel can make some modifications to the corresponding parts on the premise of ensuring the safety of vehicle use.

Case 2

Fault phenomenon: A 2007 Dongfeng Nissan Yida 1.6L sedan, equipped with HR16DE engine and RE4F03B automatic transmission, with a mileage of 30,000 km. According to users, the engine of the car will stall during normal driving.

Inspection and analysis: During the road test, it was found that the fault phenomenon was quite obvious. The engine stalled 3 times in a distance of about 2 km. Each time the stalling occurred when the vehicle was waiting for a red light, as if the engine power gradually disappeared and stalled. When the shift lever was put into D gear when parking, the engine sometimes had obvious shaking. When the shift lever was put into P gear and N gear, the engine worked normally. Connect Nissan’s special fault diagnosis instrument CONSULT-Ⅲ for diagnosis, and the system had no fault code storage. Entering the engine data flow detection (Figure 4), it was found that the oxygen sensor voltage was low (only 0.07 V) and did not change, and the air-fuel ratio varied between 108% and 117%. The engine idle speed was unstable, and the engine idle speed jitter was obvious when the air-fuel ratio value became larger.

Figure 4

After communicating with the user, it was learned that the vehicle had undergone electronic throttle cleaning and intake system non-disassembly cleaning during the last maintenance. Through the analysis of the data flow, the oxygen sensor and air-fuel ratio data indicate that the mixture is too lean. Because the intake system has been checked for leaks, the possibility of too little fuel injection should be considered. So the fuel injector was checked. After the maintenance personnel removed the fuel injector, no obvious blockage was found, but 3 to 4 spray holes in each fuel injector were black.

Troubleshooting: The fuel injector was cleaned and the atomization of the fuel injector was observed. It was found that all 4 fuel injectors had poor atomization. After cleaning the fuel injector, the vehicle was installed, the test run was troubleshooting, and the engine data flow returned to normal (Figure 5).

Figure 5

Review and summary: In fact, many automotive electronic control system faults can use the engine data flow to determine the fault location. For example, the air-fuel ratio and oxygen sensor voltage data can be used to analyze that the injection volume is too small, and then a solid theoretical foundation is needed to verify our judgment.