The mass-airflow signal is out of the expected range relative to other engine data. All 987 engines (M96/M97 and 9A1 DFI) are MAF-based, so a dirty or drifting MAF skews fuel trims and is a common trigger for lean codes (P1128/P1130 on 987.1, P0171/P0174 on 987.2).
SYMPTOMS
- Check-engine light
- Rough idle
- Hesitation
- Power loss
- Economy loss
LIKELY CAUSES
- Dirty or failing MAF element
- Intake leak after the MAF
- Dirty/restricted air filter
- Intake restriction
DIAGNOSIS STEPS
- Inspect and clean the MAF element (MAF-safe cleaner)
- Check for intake leaks between MAF and throttle
- Compare MAF g/s to expected at idle and load
- Replace the MAF if it stays out of range
RELATED PARTS
- MAF sensor
- Air filter
- Intake boots