The Powertrain Control/Emissions Diagnosis (PC/ED) manual has been revised for diagnosing electronic throttle bodies (ETBs). The ETC_ACT and ETC_DSD PIDs should not used to diagnose possible ETB concerns. The IDS has a limited refresh rate when reading these PIDs and cannot display quickly enough to validate a concern. The PCM automatically monitors these inputs more accurately and will set diagnostic trouble codes (DTCs) when appropriate. Using these PIDs for diagnostics will lead to inaccurate results and improper ETB replacements. If a concern is intermittent and no DTCs are present, refer to historical DTCs and the PC/ED, Section 3 No DTCs Present Index chart for further information.
full bulletin at NHTSA ↗2009 Mercury Mariner engine problems
moderate 22 complaints filed with NHTSA · avg repair $3,100 · see engine across all vehicles →
Failure mileage
Complaints
22
Recalls
0
Avg fix
$3,100
What stands out
Of the 7 model years of Mercury Mariner we track for engine problems, this one carries the most owner complaints on file — 22.
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.
FORD: DUE TO AN INTERMITTENT LOSS OF RPM OR LACK OF ACCELERATION, IN SOME VEHICLES, WITH ILLUMINATED WRENCH LIGHT, DIAGNOSTIC TROUBLE CODES (DTCS) P2111, P2112 MAY OR MAY NOT BE STORED IN POWERTRAIN CONTROL MODULE (PCM). MODELS 2009-12 ESCAPE, MARINER, FUSION, MILAN.
full bulletin at NHTSA ↗FORD/LINCOLN/MERCURY: SOME VEHICLES MAY EXPERIENCE AN ILLUMINATED MIL OR SAFETY STOP NOW MESSAGE, OR A NO START CONDITION OR POSSIBLE MISFIRE OR ROUGHNESS AT IDLING THROUGH 2000RPM OR A LACK OF ACCELERATION. MODELS 2009-12 ESCAPE, 2009-11 MARINER, MILAN, 2010-12 FUSION, 2011-14 MUSTANGS, 2013 C-MAX, FUSION, MKZ HYBRID.
full bulletin at NHTSA ↗FORD: THERE MAY BE A LEAKING/STUCK CANISTER PURGE VALVE WHICH CAN CAUSE MULTIPLE DRIVING SYSTEMS. THE MALFUNCTION LIGHT MAY BE ON WITH OR WITHOUT STORED TROUBLE CODES.
full bulletin at NHTSA ↗FORD: VEHICLES MAY RUN ROUGH, HARD START AFTER REFUELING, CLICKING NOISE UNDER HOOD, AND HAVE TROUBLE CODES STORED.
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
The 2009 Mercury Mariner's engine system shows a consistent pattern of stalling without warning. Owners describe complete loss of power at idle, traffic lights, and highway speeds—most restart easily after neutral-and-key restart, but the sudden nature creates safety hazards in multi-lane traffic. Several owners report the check engine light comes on or stays off despite failures, and diagnostic codes when present point to VCT solenoids (P0022) and throttle actuator faults (P2111), though many failures yield no codes at all.
Separate from stalling, owners report loss of acceleration while the engine is running—the vehicle enters "limp mode" and slows involuntarily until restarted. Throttle body replacement appears in multiple repair records, though one case involved a throttle body replacement that did not prevent another stall just 500 miles later.
Transmission issues appear early in ownership: hesitation on acceleration, rough shifting, and lurching into gear after a delay. One owner documents fluorescent ATF leaking from a failed air conditioning condenser, which compromises transmission function if unrepaired. Dealers blamed normal transmission behavior or attributed stalling to battery and fuel filter replacement—repairs that did not resolve the problem.
Ford references a service bulletin for VCT solenoid replacement and an Extended Coverage Program (NOTICE #13N03) for electronic throttle body issues, but characterizes these as "customer satisfaction" programs rather than recalls. Owners out of warranty face diagnostic and repair costs in the $600+ range for failures the manufacturer has acknowledged in internal bulletins.
Same Mercury Mariner engine reports on nearby years: 2010
Failure modes owners describe
Engine stalling (random)
Engine cuts off or shuts down completely while driving at various speeds or while idling, without warning. Vehicle typically restarts easily after shifting to neutral and turning key, or after waiting briefly.
When: Throughout ownership; reported from early months through higher mileage (up to 79,000 miles); occurring at idle, low speeds (30-35 mph), moderate speeds (45-70 mph), and highway speeds (65-70 mph)
Symptoms owners cite: Complete loss of engine power while driving; Stalling at red lights or stop signs; Stalling while idling; Stalling when accelerating from stop; Stalling when slowing down; Stalling on inclines or downhill; Engine restarts easily after restart attempt
Codes mentioned: P0022 (VCT Solenoid fault), P2111 (Throttle Actuator System stuck open), No codes detected (in several cases)
Repairs/costs cited: Owners cite replacement of VCT solenoids (~$620 at 29k miles), battery replacement (incorrect diagnosis), gas filter replacement (incorrect diagnosis), throttle body replacement, relay switch replacement; many dealerships found no fault codes or could not diagnose the issue
Recalls/TSBs owners mention: Ford dealership service bulletin exists for VCT solenoid replacement (no official recall); NHTSA Investigation PE13003 mentioned regarding throttle body; Extended Coverage Program NOTICE #13N03 (Electronic Throttle Body) referenced as 'customer satisfaction program' rather than recall
Loss of engine power / limp mode
Engine remains running but vehicle loses acceleration capability or enters 'limp mode,' restricting power output. Power returns after stopping engine and restarting.
When: Reported at 50-72,000 miles; occurring during highway and country driving at moderate to high speeds
Symptoms owners cite: Sudden loss of acceleration despite engine running; Vehicle slows from 70 mph to 20 mph independently; Unresponsiveness when pressing accelerator pedal; Engine enters limp mode, requiring restart to resume normal operation; Happens at speeds of 45-70 mph
Codes mentioned: P2111 (Throttle Actuator System stuck open)
Repairs/costs cited: Owners report throttle body replacement as repair; some cases not diagnosed or repaired
Recalls/TSBs owners mention: Extended Coverage Program NOTICE #13N03 (Electronic Throttle Body); service advised throttle body replacement
Transmission hesitation and shifting issues
Transmission hesitates when accelerating or shifting, particularly after coasting or waiting at stops. Vehicle lurches into gear after brief delay. Owners report transmission fluid loss with no clear explanation.
When: Starting in 2010; reported within first months of ownership; transmission fluid loss occurred early in ownership
Symptoms owners cite: Vehicle hesitates when accelerating from stops; Unresponsive delay after coasting or waiting for light to turn green; Vehicle lurches into gear after hesitation; Transmission shifts roughly; Transmission fluid leaking from condenser area; Transmission solenoid failure
Repairs/costs cited: Intake manifold removal for repair; transmission solenoid replacement; transmission fluid replacement; fluorescent oil (ATF) leak from condenser due to failed air conditioning condenser; owners report repair costs increasing due to transmission fluid loss damage
Recalls/TSBs owners mention: Dealer stated this is normal behavior for 6-speed automatic ('that's the way they work'); no warranty coverage cited as vehicle is out of warranty at 2,000 miles
Check Engine Light and electrical anomalies
Check Engine Light illuminates; in some cases dashboard lights flicker or turn off without operator input. Service sensor light also reported. In one case, heat/AC settings changed without input.
When: Reported at 29,000 miles and higher mileage; multiple instances spanning 2013-2014
Symptoms owners cite: Check Engine Light illuminates and may reset without repair; Service sensor light illumination with stalling; Dashboard lights turn off and back on repeatedly; Heat and A/C settings change without operator input; Yellow wrench light illuminates in lower left portion of dashboard
Codes mentioned: P0022 (VCT Solenoid fault), P2111 (Throttle Actuator System stuck open)
Repairs/costs cited: Owners report VCT solenoid replacement (~$620); some dealerships reset computer without repair; one owner reports computer 'update' performed in April prior to stalling episodes
Recalls/TSBs owners mention: Service bulletin exists for VCT solenoid replacement; no recall issued despite owner assertion of widespread problem affecting 2009-2011 Mariners and Escapes
Rough running and sputtering
Engine runs roughly, sputters intermittently, and may cause vehicle to vibrate. Occurs after stalling incidents or throttle body replacement in one case.
When: Reported at 30,000+ miles; occurring after stalling events and after repair attempts
Symptoms owners cite: Vehicle rides rough; Intermittent sputtering; Vibration in gas pedal at 42 mph (could not be verified by dealer)
Repairs/costs cited: No specific repair noted; owner reported issue persisted; vibration issue 'could not be verified' by dealership
Synthesized from 22 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 0 most recent
Had engine trouble with your 2009 Mercury Mariner?
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 2009 Mercury Mariner?
It's a documented issue but not catastrophic. 22 complaints have been filed. Repairs average $3,100 and most owners catch it before it causes a breakdown.
At what mileage does the engine typically fail?
Across the 22 complaints that reported odometer mileage, most engine failures cluster between 38,000 and 78,600 miles, with the median around 67,480. A quarter of owners report trouble before 38,000; a quarter make it past 78,600. Maintenance history matters more than the odometer alone — this is the reported failure window, not a guarantee.
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/2009/Mercury/Mariner.
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.