Failure phenomenon: a 2003 annual Shanghai Volkswagen Passat 1.8T sedan, equipped with ANQ engine. The owner of the car suddenly accelerated reflect weakness, nausea phenomenon in a moving way, and the fastest speed can reach 100 km / h, and fuel consumption is significantly increased.
Check Analysis: The author next car road test, it was found indeed as the owner of the Symptom: engine acceleration shivering, nausea clear, tempered and slow refueling. Found using OFF detecting cylinder 3 does not work cylinder, the ignition coil 3 exchange a normal cylinder, but the engine is still shaking, nausea fuel, the engine rapid acceleration tempering.
Then the author uses gold gallops into the engine fault diagnostic system using a fault code read function 02, found the following failures: 00543mdash; mdash; exceed the maximum speed; 00544mdash; mdash; exceed the maximum supercharging pressure (non-sporadic ); 01249,01250,01251 and 01252mdash; mdash; 1,2,3 4-cylinder injector and fault (open circuit or short to ground) (occasional); and a right camshaft adjustment failure (non-sporadic).
then I quit 02 03 function after function into the clear fault codes, the system is normal. However, the speed road test found only reach 120 km / h. 02 into the idle stop function when reading fault codes, found that the system is normal. 06 into the stream of measurement data function, display group 01: Zone 2, the engine load 1.7 (0.5 to 1.5 standard should be); Show Group 02: 3 region, fuel injection pulse width from 3.1 to 4.1 (standard should be 1.00 to 3.00); 4 region, the air flow rate of 4.1 ~ 4.8 g / s (standard should be 2.0 ~ 4.0 g / s); 04 display group: region 2, an idle air flow (the adaptation value) 1.6 g / s, (~ standard value should be -1.1 1.1 g / s); display group 07: 1 region, lambda; -25 controlling percentage (percentage of normal value should be -10 to 10 percent); zone 2, lambda; change in sensor voltage (0.2 ~ 0.8 V) In addition to the basic slowly within the normal range.
According to the above fault code and data flow analysis, the author of the following specific inspection.
If the pressure is too lowBlended gasoline will cause too thin, causing temper, so I first check the fuel pressure. After the ignition switch is turned off, fuel pump disconnect the fuse, the engine start releasing the fuel pressure in the fuel system piping, connect the fuel gauges, a fuse plug in starting the engine fuel pump, fuel pressure is shown as 296 kPa, in the normal range Inside. Road test fuel pressure is also normal. Then check the injector, found where the wire harness worn injector at the rear end of the engine, the fuel injector line signal line. I believe that the 3-cylinder misfire fault code is thus caused damage to the wiring harness. So the harness properly.
If the engine intake duct leak, make too lean mixture in the cylinder, causing the engine can likewise be tempered. So I checked the intake system, the intake manifold is not found and other parts of the leakage or malfunction, then the air flow meter fault analysis concluded that the data stream, then replace the air flow meter.
ignition timing system also cause a problem like mixture too lean or tempered fault, and so the author of the cylinder pressure and ignition systems were examined. Each cylinder pressure measurements were about 1 100 kPa, the deviation of each cylinder is not, the normal range; check the spark plug and the ignition spark plug gap gauge found, so in addition to the breakage of the cylinder 3 has an ignition coil replaced the previously mentioned 4 spark plug. Check the ignition timing is correct, the failure test has improved but still not smooth acceleration.
The author again when he heard when the test ldquo; hissing rdquo; voice, hear the audio from the three-way catalyst when the accelerator pedal is stepped on the lift. After removing the three-way catalyst, start the engine, another trial found no shaking of the vehicle accelerator pedal is depressed, tempering, feels very smooth. Dismantling the three-way catalyst, clogging was found therein.
troubleshooting: After replacing a catalytic converter test, strong acceleration of the vehicle, the vehicle speed to reach 180 km / h, engine data streams detected signal is normal, fault completely ruled out.
reviewed: review of this entire fault diagnosis process of elimination, struggling, and finally analysis determined to be bad and the air flow meter overrun spark plug gap, in particular the cylinder 3 caused by the ignition coil of the engine exhaust does not work too much oxygen. The oxygen sensor signal to the engine control unit in a hybrid vapor lean (high oxygen) in the exhaust gas, ECUFuel injection pulse width in accordance with the feedback signal increases, the incomplete combustion in the combustion exhaust gas in the exhaust manifold and the catalytic converter, a long time resulting in the final three-way catalyst fouling and damage, causing the engine to cause poor exhaust It produced a series of fault phenomenon. Therefore, the vehicle can not be the ultimate cause of fault is the high-speed running three-way catalyst damage caused by fouling.
(Ying-Shi Joe)