Coke and Prevention
Speaking EFI car, maybe a layman can say car one or two its advantages, such as energy conservation, environmental protection and so on. But with the popularity of EFI car in the world, some of its unique fault has cropped up, the most typical is the coking phenomenon.
Carbon can be divided valves, combustion chamber and the intake manifold .
Valves, combustion chambers organic carbon
Decided by EFI engine control characteristics, when each work are the first cylinder fuel injection re-ignition, when we turn off the engine immediately the moment the ignition is turned off, but this cycle gasoline ejected work can not be recovered, can only be attached to the valve and combustion chamber walls, gasoline likely to be volatile, but gasoline wax and varnish, but stayed long run gasoline wax and varnish piled thick, hardened after repeated heating on the formation of coke. If the engine is burning oil poor, or raise the quality of gasoline impurities, then the valve is even more serious and the formation of coke and faster. Because carbon sponge-like structure, when the valve after the formation of carbon injected into each cylinder of fuel will have a part to be adsorbed, making real mixture into the cylinder gas concentration thinning, resulting in poor engine work, there difficulty in starting, idling is not steady, poor acceleration, emergency refueling temper, excessive exhaust, fuel consumption increases and other anomalies. If the valve can cause serious Mifengbuyan make a cylinder cylinder pressure while completely failing does not work, even blocking the valve so that does not return. At this valve and piston movement will produce interference, and ultimately damage the engine.
Carbon intake pipe machine
Since the entire work of the various piston engines are not synchronized, when the engine is turned off, some of the cylinder intake valve is not fully closed, some of the continuous evaporation of unburned fuel oxidation, especially in the intake pipe to produce some of the more rear throttle Soft black carbon. On the one hand these carbon intake pipe wall will become rough, intake swirl generated in these rough places, affecting the air quality effects and mixed into the gas. On the other hand, these machines will be blocked carbon idle channel is idle speed control device catching or exceeds its adjustment range, so that will cause low idle, idle trembling, speed various ancillary devices are failure to close the oil off the car, exhaust exceeded, charges oil phenomenon
If you encounter while driving full speed, no-load refueling tempering anxious, cold start problems phenomenon, then your car’s valve is likely to have a coke. If you find low idle and idle the car shaking, when depressing the accelerator card, no idling after changing the battery, then your car’s intake manifold has coke very serious. With the above phenomenon should go to a professional repair shop check the car up.
In the automotive repair diagnostics for carbon intake is very simple, as long as the throttle removed can clearly see the extent of the coke. But for the diagnosis of valve coke has always been a problem, in general, in the professional repair shop, there are three diagnostic methods.
Disintegration of the Act
That is the engine apart, check for coke production. This is very intuitive, but time-consuming, and no matter what part each time there will be more or less disassembly affect its performance, shorten its life.
Remove the spark plug or injector, using an endoscope to observe the extent of the valve coke. This method is very convenient, but the cost of the endoscope is no trivial matter, and its usefulness in the maintenance is not very wide, so not all of the maintenance companies are equipped with the device.
Feedback voltage changes observed
Using diagnostic computer to read phenylephrine sensor feedback voltage changes, thus indirectly detect the presence of carbon deposition. Generally the normal oxygen sensor feedback voltage is between 0.3 ~ 0.7V fluctuations, and should have alternated eight times and how great the little finger within 10 seconds. Once the valve produces carbon, oxygen sensor feedback voltage fluctuation becomes large, such as increased from 0.3 ~ 0.7V into 0.1 ~ 0.9V. And the center voltage value becomes larger, while the change in frequency will slow down. Oxygen sensor diagnostic computer to read the feedback voltage variation method saves time and effort, but if the car itself, control system failure, it is not very accurate as a basis to judge, but also misleading no idea troubleshooting experience personnel. Then there is this method only for closed-loop EFI car use, should only closed-loop control system was equipped with oxygen sensors.
In the automotive repair for the diagnosis of coke has always been a problem, and if so the owners themselves to tell whether there is even more difficult to produce coke, instead of a problem and then repair is better to take preventive measures, by means of routine maintenance to keep performance of the vehicle in normal use. Here are a few to reduce and prevent carbon deposition method
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