My old Passat, Shanghai Volkswagen, has appeared twice in normal driving recently, with jitter and abnormal noise. coax

Causes of unstable idle speed of automobiles;

Throttle oil accumulation and throttle carbon accumulation, dirty air inlet and blocked air inlet will all cause idling, and throttle carbon accumulation or engine oil is the most common reason for idling instability.

Spark plug failure: The weak spark caused by the failure of individual spark plugs can also lead to carbon deposition, and the spark plug activity can be restored by cleaning, but some spark plugs have a fast life and their performance will be reduced.

Oil circuit blockage: there are also oil circuit blockage and intake pipe failure represented by fuel injectors. When the fuel path represented by the fuel injector is blocked, the fuel supply pressure is insufficient, the fuel atomization is poor, the mixing ratio is unbalanced, and the combustion is incomplete, which leads to related failures.

Specific solutions to idle jitter:

1, engine carbon deposit is serious. The most common cause of idle jitter is excessive carbon deposition in throttle or injector. When there is too much carbon deposit in the engine, the gasoline sprayed by the fuel nozzle will be absorbed by the carbon deposit during cold start, which leads to too thin mixture and difficult start. In this case, it is easy to hit the car only if the gasoline absorbed by carbon deposits reaches saturation.

After landing, the gasoline adsorbed on the carbon deposit will be sucked into the cylinder by the engine and burned, and the mixture will become thicker. When the mixture is thin and thick, it will cause idling jitter after cold start. The lower the air temperature, the greater the amount of oil required for cold start, and the greater the influence of carbon deposition on cold start. The solution is to clean up the carbon deposit on the throttle and the fuel nozzle.

2. The ignition system does not work well, and the ignition condition of the spark plug is not good, which will also lead to engine idling jitter. If there is a problem, check whether there is a fault in the ignition system and whether there is too much carbon deposit in the spark plug.

3. The oil pressure is unstable. If the engine carbon deposit has been cleaned, the throttle has been cleaned, or the spark plug has been replaced, there is still the problem of idle jitter. It is recommended to go to 4S shop to check whether the fuel supply pressure and intake pressure sensors are normal. If the oil supply pressure of the oil pump is abnormal or the value of the intake pressure sensor is wrong, it will also cause the problem of idle jitter.

Solutions;

The best way is to clean the oil circuit and clean it regularly. There is no specific experience in engine development parameters from new cars. In addition, with the continuous improvement of emission standards, it can not adapt to the changes of fuel. It is impossible for all engine manufacturers to solve this jitter problem in a short time. In addition, the fuel quality is not very good or the fuel storage time is too long at the beginning of the new car, which leads to the rapid increase of colloidal components in the oil circuit, which will continuously pollute the fresh fuel, resulting in no good fuel to participate in the combustion in the later stage, resulting in excessive carbon deposition. Only by maintaining a clean oil circuit can most problems be gradually alleviated. Using fuel additives such as PNF stock solution can solve the above problems caused by carbon deposition.