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P1127

Long Term Fuel Trim Multiplicative Air System Low.

  • Kia
  • Powertrain
  • Manufacturer code
  • Medium severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
1
AreaFuel and air metering
27
FaultThe specific fault in that area

What it means

On a Kia, P1127 means the engine control unit has seen the long term fuel trim in the multiplicative (air-related) part of the correction drifting too far in the lean-correcting direction, so it is taking fuel away. This usually points to the mixture running richer than expected, or to the air measurement being read too high. The exact trim limits and the sensors used depend on the model and engine.

Symptoms

  • Engine warning light on
  • Rough or unstable idle
  • Higher than normal fuel consumption
  • Smell of fuel or black smoke from the exhaust
  • Hesitation or poor pickup under load
  • Possible failed emissions test

Possible causes

  • Mass air flow or manifold pressure sensor reading too high, or contaminatedlikely
  • Leaking or sticking fuel injector delivering too much fuellikely
  • Fuel pressure too high, such as a faulty regulator or pressure control fault, where fittedpossible
  • Restricted air filter or intake duct, or an air intake fault giving a misleading airflow readingpossible
  • Faulty upstream oxygen sensor giving a false lean signalpossible
  • Engine coolant temperature sensor reading falsely cold, causing over-fuellingpossible
  • Charcoal canister purge valve stuck open or fuel vapour entering the intakerare

How to diagnose

  1. Read all stored and pending codes and the freeze frame data, noting load, engine temperature and speed when the code set.
  2. Inspect the air filter, intake ducting and sensor connectors and wiring for damage, contamination or loose fit.
  3. View live data for long and short term fuel trims at idle and at around 2500 rpm, and compare airflow readings with expected values for the engine.
  4. Check the coolant temperature reading against actual temperature on a cold engine and again when warm.
  5. Check the upstream oxygen sensor signal for correct switching and response.
  6. Test fuel pressure against the manufacturer specification for that model and check for injector leakage or excess fuel in the oil.
  7. Test the purge valve for sticking open and check for fuel vapour reaching the intake.
  8. Clear the code after repair and road test, rechecking that the fuel trims are back within normal range.

How to fix

  • Clean or replace the mass air flow or manifold pressure sensor if it is found to be faulty or contaminated.
  • Replace leaking or faulty injectors, and change the oil if it is diluted with fuel.
  • Repair the fuel pressure fault by replacing the faulty regulator or pump assembly as the model requires.
  • Replace a blocked air filter and repair any intake restriction or ducting fault.
  • Replace a faulty oxygen sensor or coolant temperature sensor, and repair any damaged wiring or connectors.
  • Replace the purge valve if it is stuck open.

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but fix it soon. Running rich for long can foul spark plugs, damage the catalytic converter and dilute the engine oil.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.

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