как правильно проверить лямбду.... и убедиться что действительно работает...?

_________________
audi200 mc quattro=>> audi A6 2.5 TDI mono -- Skoda superB 2013

Vitali Narva
O2 SENSOR - TESTING

If the O2 sensor wire is disconnected with the engine running, the ECU usually has a 0.45 V reference voltage on the ECU wire connecting to the O2 sensor. The ECU will switch over to a basic idle mixture setting with the O2 sensor disconnected. In the CIS fuel injection 10V Turbo engines, the frequency valve duty cycle will be set to 50% when the O2 sensor is disconnected. The ECU O2 signal wire is the large green wire with male and female spade connector under the rubber boot. This rubber boot is near the passenger side fender rim next to the fuel distributor on the 1986-88 T/Q, and early 1989 200TQ. The later 89-90 200T/Q with the dual knock sensors and the 1991 200T/Q's (10V and 20V engine) have this rubber boot connection on the back engine firewall area on the bracket with the other color coded connectors.


One test you can do with the O2 sensor wire connected to the ECU, is to use an oscilloscope to measure the O2 sensor voltage and then force the mixture rich with the slow addition of propane into the intake system. The O2 sensor voltage should rise up to at least 0.85 volts. Then force the mixture lean by creating a huge vacuum leak and measure the O2 voltage transition time when the voltage drops from high to low.


To quickly force the mixture lean, you can pull off a large hose from the intake manifold, or remove the oil cap from the valve cover (10V Turbo only). This will make the engine stall but you can capture the O2 voltage response on the digital oscilloscope.


Typical transition times are around 25-50ms, the rule of thumb is that the O2 sensor transition time from 0.6V to 0.3V or from 0.3 to 0.6V should be under 100ms. The O2 sensor will have a different transition time going from rich to lean than from lean to rich, if I remember correctly the rich to lean transition is slightly longer.


You can use a Digital Multimeter (DMM) to measure the O2 sensor voltage with the sensor connected to the ECU, but the meter may not respond quickly enough to see the voltage go up and down. It is important to know what the input impedance is of the meter you are connecting across the O2 sensor or for that matter across any of the ECU inputs/outputs. Most modern DMM's have a 10 Mega-ohm input impedance. Many of the older analog meters have a input impedance down below 100K ohms. These older meters "may" work once your O2 sensor is warmed up as the impedance of the O2 sensor usually drops to 5-20k ohms.


If your DMM has a "analog" type bar graph feature, you can measure the O2 voltage and see changes, as this bar graph display responds quicker and this can be used to monitor the O2 sensor voltage as it swings high and low when the ECU/fuel system is in closed loop operation.


If the DMM has a "zero" feature to zero out the bar graph reading with a voltage applied, you can connect the DMM to the O2 sensor wire and turn on the ignition before starting the warm engine. The DMM should read ~0.45V with the meter connected to the O2 sensor wire with the ignition on, but with the engine not running. Now zero out the 0.45V reading, and start the engine. The DMM bar graph should oscillate up and down around this 0.45V reference voltage 1 to 2 times per second, indicating that the system is in closed loop operation.


It is important to understand that if the DMM or oscilloscope shows the O2 sensor voltage stuck high or low and not oscillating up and down, that the sensor may be working correctly. The real problem may be mechanically related (lean condition from vacuum leak) or engine fuel system may have a problem (rich mixture from fuel pressure being too high). When the engine is running very lean (low O2 voltage) or is running very rich (high voltage) the ECU can not tweak the mixture enough to compensate for these problems. The O2 sensor heating element could also be defective, and this can cause a cold O2 sensor at idle with no fluctuation in output voltage.

_________________
Viber +375 29 2761658

O2 SENSOR PROBLEMS

One problem that affects the O2 sensor operation is contamination or poisoning by silicone, this shows up as a fine white powder on the tip of the sensor and will reduce the voltage output of the sensor when the mixture is rich, and this will cause a loss of fuel economy and increased CO and HC emissions. You may also see a negative voltage developed under lean operation when the sensor is poisoned by silicone. This poisoning causes the sensor to see a lower proportion of Oxygen.


The slots in the tip of the O2 sensor can also get partially clogged with carbon which will increase the response time. This will cause the O2 voltage change to slow way down, taking 3-4 seconds to go up and down, instead of changing in less than a second. This slow response can cause a varying idle speed and varying idle mixture. This slow response will show up as a varying idle speed and varying idle mixture. The exhaust gas Carbon Monoxide (CO) reading will not be steady at idle when read by an exhaust analyzer. This can also cause some light surging under light acceleration with the engine cold and when fully warmed up under cruise conditions.


There are several Society of Automotive Engineers (SAE) articles that have been published since the early 70's that describe in the utmost detail the operation of these O2 sensors. Each year SAE publishes 2-3 thousand articles covering the various automotive areas and is required reading for anyone looking for in-depth technical information on automotive systems.


Here is an excerpt from the 1976 SAE article #760287 "Closed Loop Control of Lean Fuel-Air Ratios using a temperature compensated Zirconia Oxygen Sensor"


"The sensor is based on the electro-chemical potential developed across a zirconium dioxide solid electrolyte when its two electrodes are exposed to differing oxygen concentrations. One electrode is exposed to the constant oxygen pressure of ambient air and the other to the oxygen pressure of the exhaust gas which varies with equivalence ratio. A voltage is produced which is a function of the equivalence ratio."


Most university libraries have the articles going many years back on micro-fiche and they should have an index that lists all the articles by subject, author and number. Go to O2 Sensor and Emission Article Listing for details. Bosch Generic 3 Wire Oxygen Sensor


Bosch makes a replacement 3 wire O2 sensor which is sold in large quantities and carries a low price. This generic O2 sensor can be used in the Audis if you use your original wiring and connectors and splice it to the wires on the new oxygen sensor.

Audi parts


I use the smaller gauge (red) butt type crimp connectors to splice the original O2 sensor wiring to the new generic O2 sensor. I cut the O2 sensor wires to have different lengths, so I can space the crimp connectors in different locations to allow them to slide inside the original wire sleeve to protect them from the elements.

_________________
Viber +375 29 2761658