This bulletin provides updated parts information and a service procedure to follow for removing accumulated carbon deposits from fuel injectors and internal engine components (e.g. intake valves and / or manifold, and combustion chambers). (This is an revised version of the original bulletin.)
full bulletin at NHTSA ↗2021 Subaru Forester engine problems
severe Owners of the 2021 Subaru Forester have filed 15 NHTSA complaints about the engine at roughly $3,100 to repair (U.S. federal records, as of July 2026). Source: NHTSA Office of Defects Investigation. See engine across all vehicles →
Complaints
15
Recalls
0
Avg fix
$3,100
| Model year | engine complaints |
|---|---|
| 2017 Forester | 23 |
| 2018 Forester | 14 |
| 2019 Forester | 60 |
| 2020 Forester | 32 |
| 2021 Forester (this page) | 15 |
| 2022 Forester | 4 |
| 2023 Forester | 4 |
1crash
2fires
1injury
What stands out
No new NHTSA engine complaint has been filed on this vehicle in over 3 years — the issue may be aging out of the active population.
Is there a fix? Manufacturer service bulletins
The manufacturer has issued service bulletins covering engine on this vehicle — documented repair instructions, service campaigns, or warranty extensions sent to dealers. A TSB isn't a recall (it's not a free safety remedy), but it's the manufacturer acknowledging the issue and how to fix it.
This bulletin provides updated parts information and a service procedure to follow for removing accumulated carbon deposits from fuel injectors and internal engine components (e.g. intake valves and / or manifold, and combustion chambers). (This is an revised version of the original bulletin.)
full bulletin at NHTSA ↗This bulletin provides updated parts information and a service procedure to follow for removing accumulated carbon deposits from fuel injectors and internal engine components (e.g. intake valves and / or manifold, and combustion chambers).
full bulletin at NHTSA ↗This bulletin announces the diagnostic procedures to be used when DTCs B1571(REFERENCE CODE INCOMPATIBILITY IMMOBILIZER CM TO ECM) and B1572(IMM CIRCUIT EXCEPT ANTENNA CIRCUIT) are detected by Keyless Access with Push Button Start(KACM).
full bulletin at NHTSA ↗This Bulletin provides the diagnostic procedure for the STARLINK® Remote Engine Start (RES).
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
The 2021 Subaru Forester engine exhibits multiple distinct failure modes across 15 owner complaints. The most frequent issue is random stalling at traffic lights, stop signs, and in stop-and-go traffic, occurring without warning lights or reproducible fault codes. Owners report the engine shuts down, then restarts after a few seconds; in severe cases, this happens multiple times per week, creating a serious traffic safety hazard. Dealers consistently find no codes and cannot identify a cause.
Separate from stalling, owners report sudden power loss during acceleration lasting several seconds before power returns. This occurs both at cold start and operating temperature, at various speeds, again without warning lights.
A known issue documented by Subaru itself is Thermo Control Valve (TCV) failure, which causes complete loss of engine power at highway speeds. Subaru extended warranty coverage on this part and acknowledges it as a common failure, but a TSB requires fuel line replacement with every TCV replacement—not always performed.
Two narratives describe engine fires, one following a minor collision and another within 300 miles of TCV replacement. A manufacturer inspector indicated the fire may have originated from a fuel leak but damage prevented confirmation.
Start-Stop system failures, intake valve carbon deposits at low mileage, and battery-related stalling round out the documented complaints. Throughout, dealer diagnostics routinely fail to identify causes or perform repairs.
Same Subaru Forester engine reports on nearby years: 2018 · 2019 · 2020
Failure modes owners describe
Engine stalling during idle and low-speed driving
Engine cuts out without warning while stopped at traffic lights, stop signs, or in stop-and-go traffic, and occasionally while driving at low speeds. Owners report the engine restarts after a few seconds, but the issue recurs intermittently. Dashboard warning lights (Check Engine, Eyesight disabled) may or may not illuminate. Dealer diagnostics frequently reveal no fault codes.
When: Between 12,500 and 34,000 miles; owners report stalling multiple times per week in some cases.
Symptoms owners cite: Complete loss of engine power without warning; Intermittent stalling at traffic lights and stop signs; Unresponsive brake and accelerator pedals during stall; Eyesight warning light and buzzer may activate; Engine restarts after a few seconds; Recurs multiple times per week in severe cases
Repairs/costs cited: Dealers unable to reproduce the issue or identify a root cause; most owners report no repair attempted. One narrative mentions fuel injector replacement without resolving the problem.
Engine power loss during acceleration
Engine loses power and drops in RPM for several seconds during normal driving or acceleration before regaining power. Occurs at various speeds and temperatures. No warning lights present in some instances.
When: Between 12,500 and 13,135 miles; owners report multiple separate occurrences.
Symptoms owners cite: Sudden loss of engine power while accelerating; Engine deceleration from 35 mph to lower speeds before regaining power; Occurs both at cold start and operating temperature; No warning lights in early incidents
Repairs/costs cited: Dealers found no fault codes in memory and no issues during road tests; no repair was attempted.
Start-Stop system malfunction
Start-Stop system fails to restart the engine when the driver releases the brake pedal. Eyesight warning light activates. Owners report having to manually restart the engine and disable Start-Stop system to regain normal operation.
When: At approximately 34,000 miles and later.
Symptoms owners cite: Engine does not restart after automatic shut-off at traffic light; Eyesight system warning light illuminates; Dashboard prompts to put car in park and press start; Manual restart required
Repairs/costs cited: No repair mentioned in narratives.
Thermo Control Valve (TCV) failure
Thermo Control Valve fails, causing complete loss of engine power at highway speeds. Subaru acknowledges this is a known issue and extends warranty coverage on the part. One narrative indicates a TSB (09-80-21) requires fuel line replacement with TCV replacement, but the referenced fuel line change may not always be performed.
When: Highway driving; one failure documented at approximately 20,000 miles.
Symptoms owners cite: Complete loss of engine power at highway speed (70 mph); Engine shuts down without warning
Repairs/costs cited: TCV replacement covered under extended warranty. TSB 09-80-21 requires new fuel line with TCV replacement.
Recalls/TSBs owners mention: Subaru extended warranty on Thermo Control Valve; dealer acknowledges failure is common. Known issue since at least 2019.
Engine fire
Two narratives describe engine fires in 2021 Foresters occurring shortly after deer collision and while parked with engine idling. One fire occurred within 300 miles of TCV replacement at dealership per TSB 09-80-21. Manufacturer rep indicated fire may have originated in right rear of engine compartment, possibly fuel-leak related, but extensive damage prevented definitive diagnosis.
When: At approximately 20,000 miles and shortly after TCV replacement (under 300 miles post-service).
Symptoms owners cite: Flames visible in engine compartment; Black smoke entering cabin through vents; Noxious, hot fumes from underneath vehicle; Vehicle burns beyond recognition in minutes
Repairs/costs cited: Vehicle totaled. One narrative notes TSB 09-80-21 explicitly requires new fuel line for every TCV replacement; manufacturer rep suggested possible fuel leak.
Recalls/TSBs owners mention: Manufacturer rep inspected fire damage; acknowledged fire may be fuel-leak related but damage too extensive to confirm.
Engine surge and carbon deposit buildup on intake valves
Engine surges during acceleration at low mileage (38,000 miles on a four-year-old vehicle). Dealer diagnosis identifies carbon deposits on intake valves causing poor fuel economy, increased emissions, and running concerns.
When: At approximately 38,000 miles.
Symptoms owners cite: Engine surging during acceleration; Poor fuel economy; Increased emissions; Running concerns
Repairs/costs cited: Intake valve cleaning required at estimated cost of $300; not covered by scheduled maintenance.
Synthesized from 15 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 1 most recent
Engine stalled 2x within 8 days at major intersections (both times), therefore blocking a lane in the intersections. Was told 1st time it was a gliche by dealership. Upon researching prior recalls for this make and model, engine stalls have been an issue. Dealership still can’t figure out issue.
Had engine trouble with your 2021 Subaru Forester?
File a complaint with NHTSA → It's free, official, and how every report above got here — owner filings are the federal safety record this page is built on.
Common questions
How serious is the engine problem on the 2021 Subaru Forester?
It's a meaningful issue. 15 complaints have been filed and the failure mode causes operational problems for owners. Repairs average $3,100.
At what mileage does the engine typically fail?
Based on the 15 complaints filed, engine issues most often appear around 24,625 miles. Some report problems earlier; some make it well past 150,000 with no symptoms. Maintenance habits matter — vehicles that received timely fluid services and were not regularly overworked tend to last longer.
What does it cost to fix?
Independent shops typically charge around $3,100 for engine repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to engine?
No active recalls currently cover engine issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.
Related
Complaint and recall data sourced from the National Highway Traffic Safety Administration (NHTSA)
public records database. Verify the raw federal record at
nhtsa.gov/vehicle/2021/Subaru/Forester.
Severity ratings are derived from reported crashes, fires, injuries, and fatalities. Repair cost estimates are
independent-shop national averages and may differ in your area. Some links on this page are affiliate links.