Injection valves
If there is a suspicion that one of the injection valves is not functioning, then you can easily find out using the LED voltage indicator and an accurate ohmmeter.
1. Remove the engine cover.
2. Disconnect the injection valve connectors.
3. Voltage test first: Connect the voltage LED (not a control lamp) to the connector pins. Start the engine: the LED in the voltage indicator should flash, if not, then no voltage is applied or the control unit connecting the ground is faulty. This test cannot be carried out with a measuring instrument.
4. Resistance check: disconnect the injection valve connectors, connect an ohmmeter to both valve contacts: if the engine is cold, the device will show 13.5-17 ohms.
5. If the value is not tolerable, replace the valve (if the measurement was taken accurately).
6. Leak test: dismantle the fuel distributor pipe together with the injection valves.
7. Injection valve connectors are disconnected, fuel lines remain connected.
8. Have an assistant crank the engine several times to activate the fuel pump and build fuel pressure.
9. Watch the injection valves: each of them should release a maximum of 1-2 drops of fuel per minute. Otherwise, replace the corresponding valve.
10. Regardless of this, you can check the injection jet and the amount of fuel injected by the valve, if necessary due to engine malfunctions.
Throttle Potentiometer
1. Disconnect the throttle potentiometer connector.
2. Using an accurate ohmmeter, measure the resistance between the potentiometer contacts.
Throttle position
|
Measurement between contacts
|
Rated value (kOhm)
|
Doesn't matter |
1 and 2
|
1,5–2,6
|
Idling |
2 and 3
|
0,75–1,3
|
Full throttle |
2 and 3
|
maximum 3.6
|
Disconnecting the connector (1), it is possible to measure the voltage supply to the injection valves (2) with LED voltage indicator. When the engine is cranked by the starter, the LEDs in the voltage indicator should flash. If not, no voltage is applied.
Air mass meter
MPI only
The photo shows an air mass meter (1) engine with a displacement of 2.8 liters and a three-pole connector (2).
The pinout of the three-pole connector is used to test the air mass meter.
1. Measurements are made with the throttle in the position «idling» And «full throttle» when the engine is not running.
2. The following nominal values must be obtained:
3. Push back the rubber lug on the air mass meter connector, the connector remains connected.
4. Connect an accurate voltmeter to the rear connector pins as described below:
5. Measurement 1: connect the test leads to the pins «2» And «3».
6. Turn on the ignition.
7. The voltmeter should show 12-14 V. If not, then there is a defect in the voltage supply.
8. Check fuse 32, if necessary, check wire from fuse 32 to terminal «3» air mass meter connector.
9. Or check the connection from the engine ground to the contact «2».
10. Measurement 2: connect the test leads to the pins «1» And «2».
11. Turn on the ignition.
12. The voltmeter should show 0.3-1.1 V.
13. Start the engine (wire stays connected). Turn off all consumers, the radiator fan should not work
14. Sequentially oscillate engine speed between idle and 4000 rpm.
15. Voltmeter should show (depending on the number of revolutions) from 1.5 to maximum 3.4 V. If not, then the air mass meter is faulty. Replace it.
Idle stabilization valve
MPI only
In the engine with a displacement of 2.8 liters, the idle control valve is located on the right side of the throttle valve.
1. Disconnect the idle speed control valve connector and connect an accurate ohmmeter to both pins of the valve connector.
2. The meter should show 7-11 ohms, otherwise the valve is faulty.
3. Deeper check of operability: dismantle the valve of stabilization of idling; connector remains connected.
4. Set the rotor in the air passage of the valve to position «open» or «closed» (do not use a metal tool for this purpose).
5. Turn on the ignition and observe the rotor: it should oscillate approximately in the middle position.
6. Check the ease of movement of the rotor: it should move due to the jerky movement of the dismantled valve.
7. In addition, it should not have nicks or scuffs.
Idle stabilization valve
MPFI only
The photo shows the idle control valve (arrow) in an engine with a displacement of 2.6 liters.
Idle stabilization valve (1) in a six-cylinder engine with a displacement of 2.8 liters is located next to the fuel pressure regulator (2), as you can see in this photo.
Attention! The idle speed control valve of a 2.6 l engine cannot be dismantled in a home workshop, since immediately after installation a so-called basic adjustment of the injection system must be carried out, which can only be done using the VAG 1551 fault reader in an Audi workshop.
If the connector on the idle control valve is disconnected within 1/2 hour after the engine was last turned off, then the malfunction «defective idle control valve» will be stored in the computer's memory (that may not have been done before).
In this valve, only the winding is checked:
1. Disconnect a socket on the valve of stabilization of idling.
2. Using an accurate ohmmeter, measure the resistance between the connector pins «1» And «4», and «2» And «3» valve.
3. If the valve is in working order, then the device should show 45-60 ohms, otherwise the valve should be considered defective.
4. Other checks cannot be done on your own.
5. If the workshop replaces the valve, it immediately carries out the said basic adjustment.
Ignition/injection coolant temperature sensor
At the rear of the engine, screwed into the coolant supply pipe, there is a combined coolant temperature sensor (1) ignition/injection systems and temperature indicator. Here is the connector (2) disconnected to check the sensor. The injection system includes connector pins «1» And «3».
The diagram shows at what temperature what value of resistance this sensor should show.
Attention! If the connector on the coolant temperature sensor on a 2.6L engine is disconnected within 1/2 hour of the last engine shutdown, the problem is «defective coolant temperature sensor» will be stored in the computer's memory (that may not have been done before).
General: the reason may be in the coolant temperature sensor, if engine malfunctions occur in certain temperature ranges. Examination:
1. Disconnect the connector on the coolant temperature sensor.
2. Measure the resistance between the connector pins with an ohmmeter «1» And «3» sensor.
3. The measured resistance is compared depending on the motor temperature with the nominal value diagram below. If the value is a significant distance outside the curves, replace the temperature sensor.
4. In conclusion, two more approximate resistance values \u200b\u200bshould be mentioned here: at a coolant temperature of 20°C, an ohmmeter should show about 2.5 kOhm, at 80°C - about 330 Ohm.
Intake air temperature sensor
MPFI only
intake air temperature sensor (3) available only in the engine with a displacement of 2.6 liters. It is located on the right rear of the engine next to the idle control valve (1) and fuel pressure regulator (2).
This diagram shows the resistance value of the sensor as a function of the intake air temperature.
Attention! If the connector on the intake air temperature sensor is disconnected within 1.5 hours after the engine was last turned off, then the malfunction «defective intake air temperature sensor» will be stored in the computer's memory (that may not have been done before).
1. Disconnect the intake air temperature sensor connector.
2. Measure the resistance between the two pins of the sensor connector with an accurate ohmmeter.
3. Compare the measured resistance versus motor temperature with the nominal value in the diagram below. If the value is a significant distance outside the curves, replace the temperature sensor.
4. In conclusion, here are the approximate resistance values: at 20°C (room temperature, engine cold) the device should show about 6.3 kOhm.
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