When an abnormal air leak occurs on engines with electronic fuel injection, idle floatation may occur. This leads to the fact that the engine speed increases with a frequency of about 3 seconds. This situation arises for various reasons. In diesel and carburetor engines, the reasons for idling floating are somewhat different. In order to get out of this situation, it is necessary to clearly define the cause of its occurrence.
Electronic injection engines have a control unit, its second name is a computer. It calculates the volume of air that enters the cylinders and opens, if necessary, the solenoid valves of the injectors for one time or another. If excess air enters, and the throttle position sensor signals that it should not be there, the temperature sensor, in turn, that the engine has already warmed up and it is necessary to reduce the flow of fuel, then the computer “leaves files” and it just unable to determine how to deal with excess air. All this leads to a violation of the automatic power supply system of the engine. Moreover, the engine speed begins to increase gradually. To neutralize this situation, you should proceed as follows. First you need to tighten the speed control screw. As a result of this action, the hole through which air enters for operation in this mode is closed. If this does not lead to anything, then it is necessary to squeeze all the rubber tubes with pliers. This manipulation is also diagnostic in nature. If, in the process of clamping any tube, the engine's operation returns to normal, then it is best to disconnect this tube. Then you need to find out from which device this tube leaves and for what reason it passes air. Most often it is a starting device, a device that maintains speed or an engine ventilation valve. If, after all the tubes are pinched by idle, the stroke still floats, then it is necessary to remove the air duct in front of the throttle valve block. Directly in front of the damper there is a hole, about 1 cm in diameter, through which air can flow bypassing the throttle valve. The reason for the passage of excess air can be a device for forced increase in idle speed. In appearance, it resembles a motor, to which two or three wires fit. There are situations when the valve of this device allows air to pass through. Carburetor engines can get into such a situation when one of the servomotors that opens the throttle valve is faulty. In diesel engines, the reason for floating idle speed, as a rule, is the sticking of the movable blades in the feed pump. The reason for this is the rust formed by the presence of water in the fuel. This happens with cars that have been idle for a long time with the engine turned off. Knowing the reason why the idling float occurred, you can try to cope with the situation on your own, if you have the appropriate experience. But it is best to entrust the technique to professionals.