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The impact of carbon deposits on automobile performance and diagnostic methods

The impact of carbon deposits on automobile performance and diagnostic methods

Feb 26,2021
The following describes the impact of carbon deposits on the performance of the car after the formation of different positions.
1. Carbon deposits on the throttle body
The carbon deposits here are mainly concentrated in the following locations: around the blades, on the back of the blades, and at the idle motor. Carbon deposits can cause idling instability, idling jitter, high idling, stalling, hysteresis, misfire and other phenomena. Carbon deposits around the blades mainly affect the rotation speed and opening angle of the blades, resulting in deviations between the intake air volume and the data calculated by the intake air flow. The fuel injection volume calculated by the computer is different from the actual demand volume. In some throttle bodies made of non-metallic materials such as plastic steel, the performance is more obvious in winter, such as Mazda cars; the carbon deposits on the rear of the blades are not easy to find and difficult to deal with. It was not until the disintegration that the number was found to be terrible, especially when the throttle angle is downward-inclined, such as Hiromoto, etc.; the formation of carbon deposits around the idle speed motor is synchronized with the blade formation, and the idle speed channel is blocked and the idle speed control device is stuck.
If it lags or exceeds its adjustment range, it will cause low idling speed, idling tremor, slow speed increase, oil removal and vehicle exhaust, excessive exhaust gas, fuel consumption and other phenomena. It is usually not easy to handle because it is located behind and on the side. Therefore, some automobile companies recommend cleaning the throttle body every 15000km, such as Beijing Hyundai.

2. Carbon deposits in the fuel injector
The formation of carbon deposits in the fuel injectors will cause a series of problems such as vehicle shaking, gasping, power drop, fuel consumption increase, and emission increase. In fact, this problem appeared in Europe and the United States as early as the 1980s. The main manifestation is that the nozzle atomization shape changes, such as the injection angle becomes smaller, or the atomization degree of the injection decreases, etc., which directly cause insufficient combustion or partial insufficiency, resulting in a series of problems. Unfortunately, with the continuous advancement of automobile technology, a new problem is once again facing us: the original single-hole nozzle is no longer used, and now all automobiles use multi-hole nozzles such as four holes. The original intention of the advancement of fuel injectors was to improve their atomization performance, but they were burdened by Chinese fuel. Many vehicles, especially Japanese cars, often had one of them, and two or even three nozzle holes were blocked, causing corresponding failures.

3. Intake valve product
Because the structure of coke deposit is similar to sponge, when the coke deposit is formed on the valve, a part of the fuel injected into the cylinder will be adsorbed, which makes the concentration of the mixture that actually enters the cylinder becomes thinner, resulting in poor engine operation, difficulty in starting, and poor idling. Stable, rapid refueling and tempering, excessive exhaust gas, and increased fuel consumption. In severe cases, the valve may not be closed tightly, and a certain cylinder will not work completely due to the cylinder pressure being too low or even no cylinder pressure, or even sticking to the valve so that it will not return. At this time, the valve and the piston will interfere with movement and eventually damage the engine. Carbon deposits on intake valves are a very prominent problem in modern cars. It is the most serious problem in all parts of the car, and all vehicles have problems of varying degrees.
If you encounter the phenomenon of slow speed increase and difficulty in cold start during driving, the car's valve may already have carbon deposits. It is found that the idling speed is low and the car trembles when idling, the card is issued when the accelerator is depressed, and there is no idling after changing the battery, then the car's intake pipe has been very serious. With the above phenomenon, the vehicle should be checked and repaired in time. At present, there are two factors in Chinese vehicles that require special attention: one is European cars, including Peugeot, Volkswagen, Audi, BMW, Mercedes-Benz, etc.; the other is in the northern part of China, where the weather is colder in late autumn, winter, and just beginning of spring. In this case, it is a concentrated flash point for driving problems caused by valve deposits.

4. Carbon deposits in the combustion chamber
Carbon deposits on the piston tops of American General Motors, Ford, and Chrysler cars, and layers of metal patterns can be seen under the endoscope. European cars and Japanese cars can usually be seen from tens of thousands of kilometers: the groove in the middle of the piston crown will be full of carbon deposits, even high in the middle and low on the sides. Carbon deposits in the combustion chamber can cause a series of problems such as knocking. Coking changes the gas flow performance, affecting the turbulence intensity, flame propagation speed, combustion rate and combustion duration in the combustion chamber. At the same time, coke deposits are a poor conductor of heat, and the temperature is always high. Continuously transfer heat to the mixture and change the temperature of the mixture, thereby changing the temperature of the final combustion mixture; on the other hand, the carbon deposit itself occupies a certain space, which reduces the normal working space of the mixture and improves the compression ratio. The overall effect is that the presence of carbon deposits increases the tendency to knock. The carbon deposits in the four parts have a side effect on the vehicle's power, economy, operating performance and emissions. For example, the throttle volume carbon causes the throttle opening to increase, fuel consumption increases, and emission performance decreases; the presence of fuel injector coke deposits increases the fuel injection pulse width and fuel consumption; the combustion chamber coke deposits directly affect the change of compression ratio. Whether the combustion is sufficient or not causes the oxygen sensor value to change, which affects the entire control system.

Coking diagnosis method
There are many methods for the diagnosis and analysis of coke deposits, and the more commonly used professional methods are as follows:
1. Disintegration method
That is to disassemble the corresponding parts of the engine to check whether there is carbon deposits. For example, remove the throttle body, remove the idle speed motor, remove the fuel injector, or remove the spark plug to check the intake valve and combustion chamber. This method is intuitive, but time-consuming and labor-intensive. The biggest problem is that every disassembly and assembly of a component will affect its overall performance and shorten its service life.

2. Endoscopy
Remove the spark plug or fuel injector and use an endoscope to observe the carbon deposits in the intake valve, combustion chamber, piston crown, etc. This method is intuitive and does not hurt the vehicle.

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