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2015 KIA FORTE
1.8L I4•FWD•AUTOMATIC•gas•G4NB
1 active safety recall on this vehicle — view recalls🏆Sponsored by Simon-Olivier Ricci
Repairs401Labor487Torque1976Fluid7DTC1836Battery1Maintenance0Recalls1
P1128moderate severityPowertrain

Long Term Fuel Trim System Too Lean

on 2015 Kia Forte 1.8L I4 · FWD

What this code means

The PCM has detected that the long-term fuel trim system correction has exceeded the lean limit. The entire fuel system is consistently lean beyond the PCM correction capability.

Symptoms

  • Check Engine Light
  • Rough idle
  • Hesitation
  • Poor acceleration
  • Possible misfires at idle

Common causes

  • Large vacuum leak
  • Failing fuel pump with low pressure
  • Clogged fuel filter
  • MAF sensor contamination under-reporting airflow
  • Intake gasket leak

Diagnostic steps

  1. Check system fuel trim values on scan tool
  2. Perform comprehensive vacuum leak test
  3. Test fuel pressure at idle and under load
  4. Clean or replace MAF sensor
  5. Inspect intake manifold gaskets

Repair notes

Find and repair the vacuum leak or fuel delivery issue causing the lean system fuel trim.

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