System Too Lean at Idle (Bank 1)
The ECU corrects the mixture with the lambda sensor. If it has to add a lot of fuel at idle, it suspects extra air is getting in.
What the car has detected
At idle the mixture correction has reached its limit: air the flow meter does not measure is getting in, or too little fuel arrives.
It is not usually dangerous, but the idle may be rough and, if it carries on, the engine may run worse. Have it checked when you can.
Symptoms
- Engine warning light on
- Rough idle
Possible causes
- Air leak after the air flow meter
- Faulty crankcase breather valve
- Dirty or blocked injectors
- Exhaust leak ahead of the sensor
Checks for the garage
- Listen for hissing or look for split hoses at idle
- Check the crankcase breather
- Check the fuel pressure and the injectors
Next step
Ask for air leaks to be found, especially at the crankcase breather, and the injectors and fuel pressure checked.
You can keep using the car and book a visit without hurry.