Engine idle check
Before checking the idle speed of the engine, do the following:
- warm up the engine (oil temperature not less than 80°С);
- check and, if necessary, adjust the ignition timing and the gap between the electrodes of the spark plugs;
- make sure that the air filter element and the oxygen content sensor in the exhaust gases are in good condition;
- turn off all auxiliary electrical equipment and air conditioning (if he is).
During the test, the electric fan of the cooling system should not turn on.
Otherwise, checking the idling speed of the crankshaft and the CO content in the exhaust gases is carried out in the same way as for the STsV «Mono-Jetronic».
Throttle position sensor test
Checking the throttle position sensor can be done both with the help of the diagnostic unit and without it.
Checking with the diagnostic unit. Connect the VAG 1551 diagnostic unit to the diagnostic block located in front of the gear lever (pic. 2-76), by connecting the black connector of the diagnostic block to the black connector of the diagnostic block, and the white connector of the diagnostic block to the brown or white connector of the diagnostic block.
Turn on the ignition. Click on the button «1» diagnostic block. On the diagnostic block, dial the number 01 and enter it with the button «Q». Click on the button «>». Dial the number 04 and enter it by pressing the button «Q». Dial «00» and enter with the button «Q». Slowly open throttle fully. Note the indications of sector 2 of the display of the diagnostic unit. Make sure. that the displayed value gradually increases when the throttle valve is opened up to ¼ of its travel, then remains constant. Check that the value shown on the display sector 3 increases smoothly throughout the entire throttle stroke from the idle position to the full throttle position. Click on the button «>». Dial the number 06 and enter it with the button «ABOUT» to end the test cycle.
When replacing the automatic transmission control unit, use the VAG 1551 diagnostic unit to coordinate the throttle position sensor with the new control unit. as below.
Connect the VAG 1551 block to the diagnostic block, as indicated above. Enter «02 Gearbox electronics». Pair until the message appears on the display «Select function XX». Click on the buttons «0» and «4» and enter the dialed number with the button «ABOUT». Do not open throttle valve. Dial a number «00» and enter it with the button «Q». This completes the initial adjustment of the system. By depressing the accelerator pedal, fully open the throttle and hold the pedal in this position for 3 seconds. Click on the button «>». To end the display, press the buttons «0» and «6».
Check without a diagnostic unit. Disconnect the air supply hose from the central injection unit. Disconnect the throttle position sensor connector (pic. 2-77). Check with an ohmmeter the resistance between the terminals, which should be:
- «1» and «5»: 520-1300 ohm;
- «1» and «2»: 600-3500 ohm;
- «1» and «4»: 600-6600 ohm.
If resistance is not within specification, replace throttle position sensor.
Checking and adjusting the throttle switch
Note. Throttle switch adjustment is only necessary when replacing the idle speed controller or the lower part of the central injection unit.
Disconnect the air supply hose from the central injection unit. Switch off the ignition. To failure by hand, drown the switch rod in the direction of the idle speed regulator and check with a feeler gauge the gap between the switch rod and the throttle opening limit screw, which should be within 0.4-0.7 mm. If necessary, set a gap of 0.5 mm with this screw. Check the resistance at the lower contacts of the block idle controller. which should be but more than 1.0 ohm with the probe inserted into the gap and equal to «infinity» with the probe removed. At the end of the adjustment, lock the throttle valve opening limit screw with glue.
Checking the intake air temperature sensor
Remove the air filter housing assembly. Disconnect the wiring harness from the sensor. Connect an ohmmeter to the leads «1» and «4» sensor and check the resistance, which:
- at a temperature of 0°C should be within 5.0-6.2 kOhm,
- at 20°C - 2.0-3.0 kOhm
- at 30°C - 1.6-2.0 kOhm
- at 50°С — 700-900 Ohm
- at 80°С — 300-350 Ohm
- at 100°C - 175-225 Ohm.
If the resistance values are out of range, replace the intake air temperature sensor.
Checking the idle speed controller
1st way. Disconnect the idle speed control connector. Attach to Pins «1» and «2» idle speed control pads (pic. 2-78) a DC source with a voltage of not more than 6 V. In this case, the idle switch rod should move to the fully retracted position. Disconnect power source.
Warning. To avoid damage to the idle speed controller, do not connect a current source with a voltage of more than 6 V to it.
Connect an ohmmeter to the leads «3» and «4» regulator pads (pic. 2-79). To the stop, drown the switch rod by hand and check with a feeler gauge the gap between the end of the idle switch rod and the throttle valve opening limit screw, which should be within 0.4-0.7 mm. If necessary, set a gap of 0.5 mm with this screw. With the gap adjusted and the probe inserted into the gap, the resistance on the ohmmeter should be in the range from 0 to 1 Ohm. Remove the dipstick and check that the ohmmeter shows «infinity». Connect the regulator connector.
2nd way.Disconnect the idle speed control connector. Connect an ohmmeter to the leads «1» and «2» regulator pads. The resistance should be 3-200 ohms. Connect an ohmmeter to the leads «3» and «4» pads.
With an open throttle R=0 Ohm, with a closed throttle R=∞.
If the resistance does not match the specified values, replace the idle speed regulator.
Checking the canister purge solenoid valve
Disconnect the valve connector and measure the resistance of its winding, which at a temperature of 20°C should be 35-55 Ohm.
Exhaust oxygen sensor test
Make sure that the type of the installed sensor matches the vehicle configuration. Sensor 1 (pic. 2-80) installed on cars with a manual transmission, sensor 2 - on cars with automatic transmission. On vehicles with a manual gearbox, with the engine running and the sensor connector connected, its supply voltage should be 12 V. The output current is 0.5-3.0 A. To check the sensor supply voltage on vehicles with automatic transmission, disconnect the sensor connector and connect the LED probe to the sensor block terminals (pic. 2-81). Start the engine at idle. At the same time, the probe LED should light up.
Pic. 2-75. Placement of nodes of the fuel injection control subsystem KSUD «Mono-Motronic» by car:
1 - controller;
2 - nozzle;
3 - central injection unit;
4 - idle speed regulator;
5 - throttle position sensor;
6 — heater of the inlet pipeline;
7 - coolant temperature sensor.
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