An Audi A6 auto scanner sedan, in the process of moving, low, normal, high-speed work, but releases the accelerator pedal the engine into the idling condition, the engine sometimes stall.
The fault diagnosis: Chengxiu car first validation failure phenomenon. Start the engine, the engine idle speed is obviously unstable, and is accompanied by serious jitter. This phenomenon may be the engine at idle when the concentration of the mixture or ignition of the problem, or the existence of a purely mechanical failure, cylinder wear, valve closed lax. In summary, the reasons for such failures are generally two possibilities: an electronic control system failure, mechanical system failures.
First VAG1551 detection auto diagnostic tool engine electronic control part, no fault code display. To read the data stream for each of the sensors, actuators, or are within a predetermined range; ignition advance angle are within the normal range, but the engine idle speed of 450 r / min ~ 600 r / min fluctuations. According to the test, you can basically exclude the possibility of failure of the electronic control part, the analysis of other factors that can cause the engine idle speed is easy to turn off: cylinder pressure; valve closed lax; intake system leak; insufficient oil pressure or oil the dirty block; dirty injector plugging or wear; idle speed control valve is blocked by dust or wear; leakage or insufficient ignition energy ignition system; spark plug adverse or failure; fuel evaporative emission control system leak; exhaust gas recirculation (EGR) system bad; jams, etc. of the exhaust gas purifying apparatus.
Measuring the cylinder pressure for each cylinder, at 900 kPa to 1200 kPa, normal; detecting intake manifold vacuum, normal; detecting fuel system pressure, but also normal; clean the fuel supply system and the injector is detected after each cylinder injector the fuel injection quantity, normal; detection of each cylinder ignition, normal; replacing each cylinder spark plug test failure is still the fuel evaporative emission control system to stop working; by blocking fuel vapor channel method to test fault still; blocking EGR the system exhaust Channel to suspend work, found fault disappears, thereby determining the fault of the car by the EGR system failure caused by
The working principle auto code reader of the Audi A6 car EGR system, the engine control unit (ECU) according to the engine speed, the load (i.e., throttle opening degree), the temperature, the intake air amount and the exhaust gas temperature control of the EGR solenoid valve open in a timely manner, intake manifold vacuum degree by the electromagnetic valve into a vacuum film-forming chamber of the EGR valve, the diaphragm Tie the EGR valve open, a small portion of the gas through the EGR valve in the exhaust gas into the intake system, mixed with the gas mixture into the cylinder participate in the combustion, in order to reduce the combustion chamber in the combustion temperature, inhibit the formation of NOx, thereby reducing the content of the exhaust of NOx. However, if the excessive exhaust gas is involved in recycling, will affect the ignition performance of the mixed gas, so as to affect the power of the engine, especially when the engine idling, low speed, low load, or cold machine, the amount of exhaust gas recirculated will seriously affect the the performance of the engine, so when the engine is in the condition above, ECU controlling the exhaust gas does not participate in recycling, to avoid the operation of the engine affected. When the engine exceeds a certain speed, load and temperature, ECU controls a small portion of the waste involved in recycling, and is involved in the displacement of the recirculated according to engine speed, load, temperature and exhaust gas temperature varies, in order to achieve control exhaust the lowest NOx content.
Structure and working principle of the EGR system analysis can be seen, the fault of the car could be the EGR solenoid valve closed lax exhaust uncontrolled been involved into the cylinder combustion, affecting the performance of the mixed gas of fire, causing the engine idling-stop; The EGR valve is closed or lax, the control of the exhaust gas from the EGR valve directly into the cylinder participate in the combustion, the impact of the ignition performance of the gas mixture, resulting in an idling-stop.
By blocking Launch X431 the the vacuum channel between the solenoid valve and the EGR valve, found fault still. Thereby determining the failure is caused due to the EGR valve closed lax. Remove the EGR valve checked and found the valve leakage; decomposition EGR valve inspection found both carbon deposition on the valves and valve seat. Originally coke led to the EGR valve closed lax.
Troubleshooting: auto diagnostic software clean carbon deposits on the EGR valve and valve seat and valve and valve seat with abrasive paste grinding, install retest the car after test does not leak, the engine idle smooth motion releases the accelerator pedal, the engine will not turn off then VAG1551 detection engine idle speed is stable at 800 r / min, the fault is completely excluded.
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