Fuel and air

P027F — Cold Start Fuel Injection Quantity Higher Than Expected

Severity: medium Drive with care, to a shop

What P027F means

P027F is set when the engine control module sees that the amount of fuel injected during a cold start is higher than it calculated. Normally the ECM sets injector pulse width using coolant and air temperature, pressure and air-fuel sensor data. If actual delivery exceeds the target, the cause may be an injector, a sensor or the module itself.

Symptoms

  • Check Engine light on
  • Rough idle or stumbling after a cold start
  • Higher fuel consumption
  • Hard starting in cold weather
  • Fuel smell or black smoke from the exhaust

Possible causes

  1. Leaking or stuck fuel injector
  2. Dirty injector with a poor spray pattern
  3. Faulty coolant or intake air temperature sensor
  4. Faulty air-fuel ratio or oxygen sensor
  5. Damaged wiring or poor connections at injectors or sensors
  6. ECM calibration or internal fault (rare)

How to diagnose

  1. Read all codes and freeze-frame data, noting any related fuel trim or sensor codes
  2. Compare coolant temperature reading on a cold engine with ambient air temperature
  3. Review fuel trims on a cold and a warm engine
  4. Inspect injector and sensor wiring, connectors, power and ground
  5. Test fuel pressure and check that it holds after shutdown
  6. Test injectors: resistance, balance, leakage and spray pattern
  7. Inspect spark plugs for signs of a rich mixture
  8. If all else is fine, check for ECM software updates before suspecting the module

Common fixes

  • Clean or replace faulty injectors
  • Replace a faulty temperature or air-fuel sensor
  • Repair wiring and connectors
  • Update software or replace the ECM if confirmed faulty

Questions and answers

What does P027F mean?

The ECM found that the engine receives more fuel during a cold start than calculated. Injectors or temperature and air-fuel sensors are the usual suspects.

Can I drive with P027F?

Short trips are usually possible, but don't delay the repair. A rich mixture raises fuel use, fouls plugs and can harm the catalytic converter.

What should I check first?

Start with the coolant temperature sensor, fuel trims and injector leakage. Also inspect wiring and connectors.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.