P0171 – System Too Lean (Bank 1)
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Symptoms
- Rough idle
- Hesitation
- Poor acceleration
- High fuel trims
- Possible misfires
Causes
- Vacuum leaks
- MAF contamination
- Weak fuel pump
- Clogged filter
- Exhaust leaks
Diagnosis
- Check fuel trims
- Inspect vacuum lines
- Test MAF
- Smoke test
- Check fuel pressure
Repair
- Fix vacuum leaks
- Clean/replace MAF
- Replace filter
- Repair exhaust leaks
- Replace pump