Baotou North Ben heavy truck accessories engine idling failure is divided into the following three cases: First, idle instability; Second, idling high; Third, idle or low idle speed.

(A) the general cause of the failure

1. Idle instability

(1) throttle device improper adjustment.

(2) idle valve improper adjustment. Idle control valve is faulty. Such as dirt coke adhesion.

(3) The conventional ignition circuit is faulty. Such as spark plug damage, ablation cracking; high-voltage lines are defective, damaged or too much resistance; distributor leakage; ignition coil work poor.

(4) air intake and vacuum system has a leak phenomenon.

(5) fuel injectors due to dirt clogging and poor work, fuel injectors leak.

(6) activated carbon tank blocked, solenoid valve damage.

(7) exhaust gas recirculation valve due to jam and often open, can not be closed.

(8) Baotou North North heavy truck accessories crankshaft vent valve (PCV) is faulty or blocked.

(9) Idle air-fuel ratio improperly.

(10) valve leakage, hydraulic tappet work in poor condition.

(11) the cylinder pressure difference is too large.

(12) ignition timing inaccurate.

2. Idle high

(1) Vacuum leakage.

(2) improper adjustment of throttle position (artificial adjustment).

(3) Idle control valve deformation or stuck.

(4) temperature control valve channel is not smooth. After the engine temperature, the valve body temperature does not rise, the valve paraffin temperature does not move, resulting in idling in the high idle state does not decline.

(5) P / N (parking / neutral) switch and fast idle valve are faulty.

3. Idle low or no idle speed

(1) throttle or idle switch adjustment properly.

(2) Idle control valve is faulty.

(3) are not allowed.

(B) the reasons for electronic control

(B) the reasons for electronic control

1. Idle instability

(1) Throttle Coke has dirt or idling actuator (idling stepping motor) is faulty (blocked).

(2) sensor lines or connectors are faulty, causing fuel injection error adjustment. These sensors are: oxygen sensors (poor heat conduction, poor power supply, head carbon black), intake air temperature sensor, intake pressure sensor (hose plug, squeeze or leak), throttle position sensor, air flow Sensors and so on.

(3) The fuel pressure regulator is faulty.

(4) air flow meter is faulty. For example, hot film is dirty.

(5) Electronically controlled vacuum switch solenoid valve is faulty.

(6) cold start Baotou North Ben heavy truck accessories injectors and related components are faulty.

(7) ECU is faulty. Such as poor internal wiring, corrosion, oxidation and so on.

(8) Assembly error. For example, the intake air temperature sensor and the idler control valve plug (Honda Accord sedan both the shape of the same size, and the distance is very close).

2. Idle high

(1) Throttle position sensor is faulty. Such as improper adjustment; or idle contact is not closed, ECU can not receive the idle signal; or sensor resistance value changes, the signal voltage to the ECU changes. ECU according to the change of the signal (not in idle conditions, but in a partial load conditions), instructions to increase the fuel injection time, so that the idle speed increased.

(2) coolant temperature sensor is faulty. Such as the sensor plug open circuit, ECU to set the temperature of the coolant instead of the value of the standard as a standard to control the amount of fuel injection to keep the speed increase; or the sensor shows the coolant temperature signal error, hot car status as Cold state, ECU to cold state as the standard instructions to increase the fuel injection pulse, so that the speed increases.

(3) ECU is faulty. Such as ECU damp.

(4) air conditioning switch signal, steering hydraulic signal (single injection engine) problems, to the ECU need to raise the idle signal, resulting in idle speed.

3. Idle low or no idle speed

(1) Throttle position sensor and connecting wire are faulty. Such as poor sensor signal.

(2) coolant temperature sensor and connecting wire is faulty.

(3) Idle stepping motor is faulty. Such as stuck.

(4) The intake air temperature sensor is faulty.

(C) troubleshooting

1. Troubleshooting of Idle Unstable Faults

Electronically controlled engine idling instability is caused by a variety of reasons. First of all, should distinguish between the engine idling is always unstable, or rhythm of the idle instability. If the engine failure for the rhythm of the idle instability, usually the individual cylinder does not work. If the speed fluctuated, mostly caused by leakage of the injector. If the engine only in the hot car or cold when the idle instability, mostly due to warm-up regulator (some cars did not) or coolant temperature sensor problems.

Eliminate the electronic control engine idling has been unstable fault, first read the fault code, and then follow the following procedures to check.

(1) check the engine cylinder work, whether the cylinder work is not good.

(2) check the intake system, the injector is leaked. The carburetor cleaning agent sprayed around the intake pipe to observe whether the engine speed changes, if any changes, indicating that the intake pipe may leak. And then check the fuel injector fixed bolt tightening, sealing how, with or without leakage phenomenon, the most common is the injector and the inlet of the joint seal is not good, so that the cylinder inhaled too much mixture, so that The mixture is thinner.

(3) Check whether the throttle is coke.

(4) Check if the idle actuator is faulty. These components are mainly throttle position sensor, coolant temperature sensor, oxygen sensor, air flow meter, idle control valve, intake air temperature sensor. Before inspecting these components, first check the wiring and fittings connected to these components for damage, breakage, and loose joints. If the line resistance between the sensor and the engine ECU is greater than 0.5Ω and less than 10Ω, repeat the measurement to avoid malfunction.

The role of the throttle position sensor is to the engine ECU input throttle position signal, it is the most closely related to the engine idling. Throttle position sensor caused by the idle instability of about 20%. This idle speed stabilizes the device. The reason is: throttle and throttle body formed between the gas path in the engine under various operating conditions should be gas, so that dirt attached to the throttle and throttle body on the speed of the engine in the idle conditions When the air supply cross-sectional area is reduced, in the same throttle opening, the combustible mixture becomes thick, then caused by idle instability, increased emissions, increased fuel consumption and other failures. The solution is to clean the throttle body, and then check the throttle position sensor.

Oxygen sensor installed in the exhaust manifold, its role is to monitor the exhaust gas temperature and oxygen content, and make it into a voltage signal to the ECU, ECU through the calculation to change the air-fuel ratio. Oxygen sensor is good or bad and the engine idling relationship is also larger. The oxygen sensor usually outputs a voltage of 100 to 800 mV. If the oxygen sensor power supply is poor, the head of carbon deposition, thermal conductivity, etc., will affect the engine idling operation, it should also focus on inspection.

The intake pressure sensor is connected to the intake manifold. The voltage it outputs varies by the pressure change in the intake manifold. When the ECU receives its voltage signal, you can calculate the engine intake. Intake pressure sensor performance is good or bad, the same will affect the engine idling operation. If the hose is blocked by oil or squeeze flat, leak, will change the pressure inside the hose, thus affecting the stability of air-fuel ratio, but also affect the engine idling operation.

Idle control valve driven by the stepper motor, its role is to adjust the intake air. If the control valve is coke, oil Zhai Huai knot, the same will affect the engine idling operation.

If the exhaust gas recirculation system is suspected to be faulty, temporarily prevent the exhaust gas from entering the intake manifold channel to check if the exhaust gas recirculation system is working. If you suspect that the air flow meter is faulty, you can use a book to gradually cover the air flow meter before the air inlet (gradually reduce the air inlet cross-sectional area) method to check the air flow meter is faulty. For the intake manifold absolute pressure sensor performance, can be used to remove the vacuum tube method to check. For the performance of the coolant temperature sensor, alternative testing can be done by adjusting the resistance. If there is no adjustable resistance, the common resistance can be used in place of the alternative test.

2. Absence is too high or too low troubleshooting

The idling control of the electronic control engine and the computer ECU accept the electric signal from the engine coolant temperature, the load, the throttle position and the like to determine the idling state. The computer ECU instructs the idling adjustment device to automatically adjust the signal according to the signal of the sensor. When the idle speed is lower than the set value, the computer ECU will instruct the idle speed adjustment device to open the air bypass channel, so that the intake air volume increases, thereby increasing the idle value. When the idle speed is higher than the set value, the computer ECU controls the idle speed adjustment device to close the air bypass channel, so that the intake air volume decreases and the speed decreases. So the electronic control engine idling too high or too low failure should be excluded from the following aspects.

(1) engine inspection. Start the engine, so that the engine coolant temperature reaches the normal temperature, turn off all the additional electrical devices, the shift lever placed in neutral position, and then from the engine dashboard to view the idle situation, whether the normal speed range, if not in the specified range , The following checks should be made.

(2) check the order. Check if there is a tightening bolt loosening or hose breakage at the intake manifold.

Check the output voltage of the throttle position sensor. Available in multimeter. Normal voltage is generally 0.4 ~ 0.5V, if not meet the requirements, can be cleaned by throttle body, and adjust its opening, so that the output voltage back to normal.

Check the operation of the idle stepping motor. If the idle speed is too low and other parts are normal, you can clean the idle stepper motor and air holes on the knot and coke to exclude.

Check the air flow meter signal.

Check the operation of the idle control valve.

Check other signal components, coolant temperature sensor and oxygen sensor.

3. Rapid diagnosis of idle speed control system failure

Idle instability, idling too high or too low, the reason is mostly electric control line or idle control valve problems. Under normal circumstances, through the following methods can quickly find the fault location.

(1) in the cold state to start the engine, fast idle system can make the engine at a relatively high speed operation (1500r / min), the engine reaches the normal operating temperature, the idling speed can return to normal, 750r / min or so. If the cold start, the idle speed can not be in accordance with the above changes, indicating that the idle control system is faulty.

(2) the engine to the normal working temperature, open the air conditioning switch, the engine idling should be able to rise to 900r / min or so, if you open the air conditioning switch, the engine speed down, indicating that the idle control system is faulty.

(3) in the Baotou North heavy truck accessories engine idling operation, the idle adjustment screw for a small amount of adjustment, the engine idling speed should not change, if the adjustment in the idle speed has changed, indicating that the control system does not work.

(4) Remove the idle control valve harness connector, measured with a voltmeter. If the engine is running, the idle control harness connector has a pulse voltage output, indicating that the idle control system does not work. If no pulse voltage output, open the air conditioning switch and then test, if there is no pulse voltage output, then the idle control system does not work.