P0171 on a 2021 Ford Escape

P0171 means the engine computer is adding more fuel than normal on bank 1 because it sees too much air or not enough fuel.

Not your vehicle? See general P0171 info.

Most common causes on the 2021 Ford Escape

Ranked from 326 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Cracked fuel injector body (NHTSA recall 25S76 / 25V467) reducing fuel delivery
High severity
The same recall that causes external fuel leaks also reduces fuel actually reaching the cylinders under demand, which reads as a lean condition; widely reported alongside rough idle and stalling on refueling.
Reported in 10 NHTSA complaints
Parts:fuel injector
2
Canister purge valve stuck open
Medium severity
Directly reported as causing a hard start from unmetered air entering the intake.
Reported in 1 NHTSA complaint
Parts:purge valve
3
Vacuum or intake leak
Medium severity
Cracked hose or loose clamp lets in unmetered air.
Common cause
4
Dirty or failing MAF sensor
Medium severity
Under-reports airflow, causing the PCM to under-fuel.
Common cause
Parts:mass airflow sensor
5
Weak fuel pump or clogged fuel filter
Medium severity
Insufficient rail pressure under load pulls the mixture lean.
Common cause
Parts:fuel pump fuel filter
6
Stuck-open PCV valve
Low severity
Adds unmetered air to the intake charge.
Common cause
Parts:PCV valve
7
Intake manifold gasket leak
Medium severity
A common lean-condition source as gaskets age.
Common cause
Parts:intake manifold gasket

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These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0171 on your car still needs shop confirmation before any repair.

Common symptoms

Check engine light
Rough idle
Hesitation
Surging idle
Poor fuel economy

What to check before replacing parts

Review short- and long-term fuel trims on bank 1

Look for: High positive trims (commonly worse at idle, improving with RPM) mean the computer is adding fuel to compensate for excess air or insufficient fuel — that pattern is this code's fingerprint.

Smoke-test the intake

Look for: Smoke escaping (or a hiss you can hear) at intake boots, gaskets, or vacuum hose connections confirms unmetered air is entering after the MAF sensor, which is the most common cause of a lean code.

Inspect the PCV hoses and valve

Look for: A cracked, split, or disconnected PCV hose, or a PCV valve stuck open, draws in extra unmetered air the same way a vacuum leak does.

Clean and test the MAF sensor

Look for: Visible dirt or oil film on the sensor element, or a grams/second reading that doesn't track expected airflow for RPM, means the MAF is under-reporting air and causing the computer to under-fuel.

Verify fuel pressure

Look for: Pressure below spec (weak pump, clogged filter, failing regulator) starves the engine of fuel and produces the same lean trim pattern as a vacuum leak — rule it out before chasing leaks.

Rather have a pro handle it? Find a vetted local mechanic.

Matching symptoms

Car Runs Rough