Checking the causes of malfunctions of gasoline engines (Skoda Kodiaq NS7)

Contents: Checking the root causes of…⬇ Checking for additional causes of…⬇

Note:

Make sure the following conditions are met:

The Engine Control Module (ECM) and Malfunction Indicator Lamp (MIL) are functioning properly.

No DTCs are stored.

The diagnostic tool data is within the normal operating range.

There are no bulletins for this malfunction.

The ECM ground circuits are clean, tightly connected, and in the proper locations.

The vehicle's tires are inflated to the proper air pressure and meet original equipment specifications.

The air filter element has no limitations.

Checking the root causes of malfunctions

1. Check that the intake air temperature (IAT) sensor/mass air flow (MAF) sensor is installed correctly.

2. Check the following fuel system conditions:

Proper fuel pressure.
Fuel injectors leaking or not functioning properly.
The fuel is contaminated or of poor quality.

3. Check the ignition system conditions below:

Incorrect spark plug temperature range or spark plug condition other than normal.
For diagnostics of spark plugs contaminated with coolant or oil.
Spray water from an aerosol spray bottle onto the secondary ignition circuit. Wetting the secondary circuit of the ignition system can help in locating damaged or deteriorated components. When water is sprayed, watch or listen for any sign of an electrical arc or misfire in the engine.
Weak spark when using EL 26792 HEI Spark Tester.

4. Check the operation of the transmission torque converter clutch (TCC). When the TCC is commanded to turn ON, the diagnostic tool should show a drop in engine speed.

5. Check the operation of the air conditioning compressor

6. Check for factors that contribute to lean or rich fuel mixture in the engine.

7. The following faults in the mechanical part of the engine:

Excess oil in the combustion chamber or leaking valve stem seals.
Incorrect compression in the cylinder.
Valves sticking or not fitting tightly.
Worn camshaft lobes.
Incorrect valve timing.
The valve springs are damaged.
Increased carbon deposits in combustion chambers. Clean the chambers with engine top cover cleaner. Follow the instructions on the cleaning product can.
Incorrect engine parts 8. Check vacuum hoses for cracks or kinks. Check for proper routing and connection of hoses as shown on the vehicle emission control system information label.

9. Check for a significant delay in spark formation using the signal from the knock sensor system.

10. Check the setting of the fuel octane switch. Check that the fuel octane switch is set to the correct octane rating for the fuel used in the vehicle.

11. Check the turbocharger system for proper operation, if equipped.

12. Check the turbocharger charge air cooler system for leaks (if such a system exists).

13. Check the following conditions of the exhaust system components:

Physical damage or possible internal failure.
Restriction in 3-way catalytic converter.

14. Check for electromagnetic interference affecting the reference circuit, which may cause engine misfires. Typically, electromagnetic interference can be detected using a scan tool by monitoring the engine speed value. A sudden increase in engine speed with little change in actual speed indicates the presence of electromagnetic interference. Check high voltage components near the ignition control circuit if such a fault occurs.

15. Check for leaks or restrictions in the positive crankcase ventilation system and at all connections.

16. Check that the Fuel Vapor Capture system (EVAP) purge solenoid valve is jammed in the open position.

17. Check the engine cooling system conditions below:

The thermostat ensures the proper temperature range.
The engine coolant thermostat heater is working properly.
Proper engine coolant level.

Note: If the problem persists after checking the above symptoms, you should check for additional causes of the problem.

Checking for additional causes of malfunctions

Detonation/noise from detonation combustion of the fuel mixture

Check if the engine is overheating.

High fuel consumption

Check for accumulation of foreign particles in the throttle bore and carbon deposits on the shaft and the throttle valve itself. Also, check that the throttle body has not been opened.

Rough, unstable or incorrect idle, engine stalls

Check engine mounts. Replace engine mount - right.

Decrease/increase speed

Check the heated oxygen sensors (HO2S). The HO2S should respond quickly to changes in throttle position. If the HO2S sensor does not respond to different throttle positions, check for contamination in the fuel, silicone, or improper use of a room-temperature vulcanizing adhesive. The sensors may have a white powder coating, which can cause a high but false signal voltage indicating the presence of incompletely burned fuel in the exhaust. The ECM reduces the amount of fuel supplied to the engine, which leads to engine misfires.

Hard start

Check the engine coolant temperature sensor (EST). Compare the value from the coolant temperature sensor (EST) with the value from the intake air temperature sensor (IAT) on a cold engine. Temperature readings from the ECT and IAT sensors should not differ by more than approximately +/- 3°C. If the ECT sensor temperature, when compared to the IAT sensor temperature, is outside the specified range, check the ECT sensor resistance.

If the resistance is not within specification, the ECT sensor should be replaced. If the sensor meets specifications, check for high resistance in the ECT circuits.

Check the operation of the fuel pump relay. When the ignition is turned on, the fuel pump should turn on for 2 seconds.

Interruptions, short-term "gaps", "twitching"

Check the fuel pressure.

Check the manifold absolute pressure (MAP) sensor.

Check the generator. Repair the charging system if the generator output voltage is less than 9 volts or more than 16 volts.

High fuel consumption

The vehicle was carrying a heavy load or was being towed.

Too often, very strong accelerations were carried out.

Check for accumulation of foreign particles in the throttle bore and carbon deposits on the shaft and the throttle valve itself. Also, check that the throttle body has not been opened.