System Too Rich (Bank 1)

What it means

The engine is receiving more fuel than it needs, and the computer has cut fuel delivery as far as it can without fixing the imbalance. The result is higher consumption and possible damage to spark plugs and the catalytic converter over time.

Symptoms5

• Noticeably higher fuel consumption.
• Strong fuel smell from the exhaust.
• Occasional black smoke on acceleration.
• Rough idle or reduced performance.
• Spark plugs covered in black soot.

Possible causes6

• Mass airflow sensor reading more air than actual.
• Leaking or stuck-open fuel injector.
• Faulty fuel pressure regulator causing high pressure.
• Coolant temperature sensor reporting a permanently cold engine.
• Severely clogged air filter.
• Weak or slow upstream oxygen sensor.

How to diagnose and fix6

1. Inspect the air filter and replace it if dirty.
2. Clean the mass airflow sensor or check its readings with a scan tool.
3. Confirm the coolant temperature reading is sensible once the engine is warm.
4. Measure fuel pressure and inspect the regulator.
5. Test the injectors for leakage.
6. Check the upstream oxygen sensor and its response speed.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

Usually a filter or sensor at low cost, rising when injectors or the fuel pressure regulator must be replaced.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.

Frequently asked questions