After replacing the timing belt, the engine jerked after the cold start.

Cold start jitter is mostly caused by poor fuel combustion. There is too much colloidal water in the fuel tank and too much carbon in the engine. The cold start is not taken to the combustion chamber, then mixed in the fuel tank and pumped into the combustion chamber. Jitter caused by poor combustion. During cold start, the gasoline sprayed by the fuel injection head will be absorbed by a large amount of carbon deposits, which will lead to too thin mixture during cold start and make the start shake.

If there is carbon deposit in the valve and intake of the engine, ECU will make a wrong judgment, because carbon deposit can absorb a proper amount of fuel. If the computer actually controls the injection of 100 parts of oil and gas, but only 90 parts actually enter the cylinder (10 parts are absorbed by carbon deposits), then even if the remaining 90 parts of mixed oil and gas are fully burned, the required power cannot be achieved, and the jitter phenomenon is inevitable.

Reasons for idling 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 the carbon deposit at the throttle and 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.