Caution! Gasoline is extremely flammable, so exercise extreme caution when working around the fuel system (see paragraph 2).
1. Check the condition of all wiring connectors related to the system. Check the condition of the intake manifold ground wire contacts. Poor ground connection conductivity is the main reason for malfunction of all electrical equipment in vehicles.
2. Check the battery charge status, as the engine control module (ECM) and sensors require a certain voltage in the vehicle's electrical system to operate properly.
3. Check the condition of the air filter element (see Chapter 1A) - a filter clogged with dirt creates additional air resistance at the intake, acting as an air damper ("suction"), reducing the engine's efficiency and impairing its fuel economy.
4. Check the operation of the fuel pump (see paragraph 3). If the fuel pump power supply circuit fuse has blown and the new fuse installed to replace the blown one has also blown, you should stop replacing the fuses and look for the cause, which lies solely in a short circuit in the circuit that this fuse protects (see chapter 12 and electrical connection diagrams).
5. Check the condition of the vacuum hoses and ensure that there are no air leaks in the intake tract, especially after the throttle body, through the vacuum hoses. Air leakage is often accompanied by a whistling sound.
6. Remove the intake air duct from the throttle body and check for dirt, carbon, varnish or other deposits inside the body, especially in the throttle valve area. How to remove the above mentioned deposits, described in paragraph. 2 paragraphs 14. The main sources of dirt and other deposits are faults in the crankcase ventilation and exhaust gas recirculation systems (see Chapter 6A).
7. After starting the engine, place the stethoscope next to each injector (see Figure 13.7).
Figure 13.7. To check the operation of the injectors, use an automotive stethoscope or a screwdriver.
An operating injector produces a steady chirping sound that increases or decreases with changes in crankshaft speed. If a stethoscope is not available, you can use a long screwdriver or even a wooden stick, rest one end against the nozzle and "listen" to its operation with your hand. If all injectors are working properly and the engine runs unevenly (misfires), it can be concluded that the injector power supply circuits are in good working order, but the injectors are clogged with dirt or carbon deposits. Chemical cleaners may help, otherwise the injectors will need to be replaced.
8. If the injector is not heard to operate, turn off the engine and disconnect the wiring connectors from the injectors one by one, measuring their resistance (see Figure 13.8).
Figure 13.8. Measure the resistance at the injector terminals with an ohmmeter.
The prescribed resistance value is given in Specifications. If the injector resistance is too high or too low, replace the injector - it is faulty.
9. If the injector does not work, but its resistance is within the prescribed limits, the cause must be sought in the ECM module or the injector power supply circuit.