Engine Oil Consumption Is Too Large Diagnosis and Repair Full Strategy

Engine oil consumption is too large diagnosis and repair full strategy

Abnormally high engine fuel consumption is a common vehicle failure phenomenon, which may involve mechanical wear, sensor failure, system disorders and other factors. When the fuel consumption of 100 kilometers rises by more than 15% compared with the normal value, it not only increases the cost of use, but also may indicate the existence of deep-seated hidden dangers in the engine. In this article, we analyze the 8 key fault sources and their targeted solutions through a systematic diagnostic process. I hope this will be helpful for your engine repair.

1.Failure causes

(1) Mechanical System Efficiency Decline

When cylinder wall wear exceeds 0.15mm, compression pressure drops from the standard value of 12-15 bar to less than 9 bar, resulting in a sharp reduction in combustion efficiency by 30%. Piston ring elasticity decline will result in an increase in the amount of oil, oil consumption per 1,000 kilometers can be up to 0.5 L. When the crankcase forced ventilation system is clogged, excessive oil vapor directly into the combustion chamber, forming a hidden oil consumption.

(2) Sensor signal distortion

When the coolant temperature sensor resistance drifts, the ECU may continue to implement the -40℃ cold start oil supply strategy, and the injection pulse width increases by 50%. Air flow meter heat film contamination, signal voltage deviation of 0.3V can lead to air-fuel ratio error of up to 20%. Signal jumps caused by oxidation of the throttle position sensor contacts can cause the engine to frequently enter the thickening condition.

(3) Abnormal Fuel System Pressure

The rupture of the oil pressure regulator diaphragm will cause the fuel pressure to soar from the standard 250kPa to 400kPa, and excessive fuel leakage through the injector. When the injector solenoid valve is not closed tightly, the static leakage exceeds 30ml/min, which needs to be replaced, and the hidden fuel consumption per 100km in this state can be up to 1.2L.

(4) Ignition system performance degradation

When the spark plug gap expands to more than 1.3mm, the ignition voltage demand increases by 5kV, and the misfire rate increases by 15%. The secondary resistance of the high-voltage coil exceeds the standard value of 15kΩ, and the decrease in ignition energy leads to incomplete combustion, and the HC content in the exhaust gas can exceed the standard by 3 times.

2. Diagnostic method

Step 1: Basic condition test

Use infrared camera to scan the exhaust manifold, temperature difference of more than 50 ℃ cylinder suggests poor sealing. Vacuum gauge to detect the intake manifold pressure, idle speed stability value should be maintained at 60-70kPa, fluctuations of more than 5kPa need to check the leakage point.

The second step: sensor data flow analysis

Connect the diagnostic instrument to read the dynamic parameters:

The coolant temperature signal should deviate from the actual water temperature ≤ 2 ℃.

Air flow meter idling value: 2.0-4.0g/s (naturally aspirated) / 4.0-7.0g/s (turbocharged)

Long-term fuel correction value exceeding ±10% is considered abnormal

Step 3: Fuel pressure system test

Install a mechanical pressure gauge and perform a three-stage test:

Idle pressure: 250±10kPa

Rapid acceleration transient pressure: 320-350kPa

Holding pressure 10 minutes after shutdown: >150kPa

Focus on checking the fuel pump check valve and regulator vacuum pipe when the pressure is abnormal.

Step 4: Injector precision testing

Use ultrasonic cleaner with flow tester, under 300kPa pressure:

The difference of oil injection volume of each cylinder should be <5%

Static leakage <1 drop/minute

Step 5: Ignition system in-depth diagnosis

Adopt secondary ignition waveform analyzer to observe parameters such as breakdown voltage (8-12kV), burning line length (1.0-2.0ms), and spark line slope. The difference in combustion time of each cylinder is more than 0.3ms need to check the valve lash.

Step 6: Mechanical system condition assessment

Cylinder pressure test needs to be carried out in the warm-up state, and the pressure difference of each cylinder is <10%. Wet pressure test, after injecting 5ml of oil into the cylinder, the pressure return value <15% indicates that the piston ring is worn, >25% suggests that the valve seal is bad.

Step 7: Peripheral system check

Every 0.2bar decrease in tire pressure increases fuel consumption by 1%. When the drag force of the brake sub-pump exceeds 50N-m, the power loss of the wheelside reaches 3%. Air-conditioning compressor bearing stall can increase fuel consumption by 8%.

3.Maintenance key points

(1) Sensor troubleshooting

Cleaning the air flow meter heat film should use special electronic cleaner, prohibit physical contact with cotton swabs. When replacing the coolant temperature sensor, be sure to use a torque wrench (15-20N-m), over-tightening will lead to shell cracking.

(2) Fuel System Maintenance Specifications

Before removing the high-pressure fuel rail, the pressure should be relieved to below 50kPa to prevent fuel spraying. Injector seals should be tested for 30 minutes of holding pressure after replacement to ensure no leakage.

4. Preventive Maintenance Recommendations

Clean the throttle body every 20,000 kilometers, reset the ECU adaptive values

Change fuel filter and check pump flow at 50,000km

Use low friction oil that meets ILSAC GF-6 standard.

Regular endoscopic inspection of cylinder carbon deposits

Timely, accurate and effective engine repair is crucial to prolonging engine life and improving efficiency. Abnormal engine oil consumption is like a metabolic imbalance in the human body, which requires systematic testing to locate the source of the disease and timely repair.