P0171 fuel bank 1 too lean

The Acura does not have any MAF, instead a MAP is used. Lean codes can be due to may different reasons and is one of the most difficult to diagnose. It could be a vacuum leak, fuel injectors, fuel rails clogging ec.

Was this code present before replacing the parts mentioned?

DTC P0171, P0172, P0174 OR P0175: FUEL SYSTEM IS TOO LEAN OR TOO RICH

NOTE: DTC P0171 = Fuel System Too Lean (Right Bank) DTC P0172 = Fuel System Too Rich (Right Bank) DTC P0174 = Fuel System Too Rich (Left Bank) DTC P0175 = Fuel System Too Rich (Left Bank)

NOTE: Troubleshoot DTC P0107, P0108, P0135, P0137, P0138, P0141, P0155, P0401, P1128, P01129, P1491 or P1498, if set, before proceeding.

1. If DTC P0171 or P0174 is set, check for:

a) Insufficient fuel pump flow or pressure.

B) Clogged or leaking fuel feed line.

C) Fuel pressure regulator stuck open.

D) Clogged fuel filter.

E) Clogged or air blocked fuel injector.

F) Fuel octane level less than specification.

G) A deteriorated HO2S-1.

H) Insufficient EGR system flow.

I) An exhaust system leak.

Repair as necessary. If no problems are found, go to step 3).

2. If DTC P0172 or P0175 is set, check for:

a) Fuel pressure regulator clogged or stuck closed.

B) Clogged fuel return line.

C) A leaking fuel injector.

D) Fuel octane level less than specification.

E) A deteriorated HO2S-1.

F) Excessive EGR system flow.

G) A leaking or stuck open EVAP purge control solenoid valve.

Repair as necessary. If no problems are found, go to next step.

3. Check fuel pressure. If fuel pressure is okay, go to next step. If fuel pressure is too high, check fuel pressure regulator and fuel return line. Repair as necessary. If fuel pressure is too low, check fuel pump, fuel feed line, fuel filter and fuel pressure regulator.
Repair as necessary.

4. Start engine and run at 3000 RPM with no load and transmission in Park or Neutral, until radiator fan comes on. Using scan tool, check HO2S-1 output data.

If voltage stays at less than 0.3 volt or more than 0.6 volt, replace HO2S-1. If voltage does not stay at less than 0.3 volt or more than 0.6 volt, go to next step.

5. Using a vacuum pump, apply vacuum to intake manifold side of EVAP purge control solenoid valve. If EVAP purge control solenoid valve holds vacuum, check EGR system. If EGR system is okay, replace fuel injectors. If EVAP purge control solenoid valve does not hold vacuum, replace EVAP purge control solenoid valve.