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full bulletin at NHTSA ↗2006 Toyota 4Runner engine problems
moderate 10 complaints filed with NHTSA · avg repair $3,100 · see engine across all vehicles →
Complaints
10
Recalls
0
Avg fix
$3,100
What stands out
Among the 5 model years of Toyota 4Runner in our records for engine problems, this one ranks #2 by owner-complaint volume.
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.
These SKUs are Exhaust Manifolds with Catalytic Converters. The customer communication requested return of unsold inventory due to a loss of CARB certification. These SKUs can no longer be sold as they do not meet CARB standards, but parts on vehicles are not effected.
full bulletin at NHTSA ↗These SKUs are Exhaust Manifolds with Catalytic Converters. The customer communication requested return of unsold inventory due to a loss of CARB certification. These SKUs can no longer be sold as they do not meet CARB standards, but parts on vehicles are not effected.
full bulletin at NHTSA ↗TSB: REVISION NOTICE July 01, 2019 Rev2: ? Applicability has been updated to 2019 ? 2020 model year Toyota vehicles. ? The Techstream Preparation and Process Overview sections have been updated. October 30, 2017 Rev1: ? Applicability has been updated to include 2018 model year vehicles. Any previous printed versions of this bulletin should be discarded. SUPERSESSION NOTICE The information contained in this bulletin supersedes SB No. T-SB-0012-13. Service Bulletin No. T-SB-0012-13 is obsolete and any printed versions should be discarded. Be sure to review the entire content of this bulletin before proceeding. Flash reprogramming allows the Electronic Control Unit (ECU) software to be updated
full bulletin at NHTSA ↗TSB: Supersession Notice. Flash reprogramming allows the ECU software to be updated without replacing the ECU. Flash calibration updates for specific vehicle models/ECUs are released as field-fix procedures described in individual Service Bulletins. This bulletin details the Techstream ECU flash reprogramming process and outlines use of the Technical Information System (TIS) and the Calibration Update Wizard (CUW). Flash calibration updates can only be applied to the vehicle/ECU combination for which they are intended. ECUs have internal security that will not allow them to be programmed with another ECU?s information.
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
The most common complaint is a persistent sulfur or rotten-egg smell from the catalytic converter, especially during acceleration and uphill driving. Multiple owners report the smell is strong enough to enter the cabin even with windows closed; one owner's child was choking from the fumes. A dealer replaced the converter in at least one case, but the problem returned within months. Toyota required a diagnostic test before authorizing repair in another case, and the vehicle never got fixed.
Timing cover oil leaks appear at 36k–38k miles. A 2007 TSB (EG049-07) confirms this is a known issue affecting multiple Toyota models. Repair quotes run $1,500–$1,900; dealers say most of the cost is labor, not the part itself.
Owners also report rusting bolts on the A/C compressor clutch assembly, beginning around 24k miles and worsening by 38k. The bolts corrode so severely they risk breaking apart during driving and damaging other components—a crash hazard. Toyota refused warranty coverage.
Additional issues include exhaust fumes being sucked into the cabin through the rear window due to automatic air recirculation, an accelerator pedal that stuck open during highway driving (the driver had to stomp it to regain control), and an engine mount weld failure that caused the radiator fan to hit its shroud and the engine to lurch forward at stops. One dealer said they couldn't address the mount problem.
Same Toyota 4Runner engine reports on nearby years: 2005
Failure modes owners describe
Catalytic converter sulfur/rotten egg odor
Persistent sulfur or rotten egg smell from exhaust, especially during acceleration and hill climbing. Reported as recurring even after factory replacement.
When: At low and high mileage; reported at 19.2k miles; recurring months after dealer replacement
Symptoms owners cite: Strong sulfur/rotten egg smell when accelerating; Smell intensifies going uphill; Smell present even with windows up; Odor detectable from interior and exterior; Odor recurs after catalytic converter replacement
Repairs/costs cited: Dealer replaced catalytic converter(s) in at least one case; problem recurred within months. Dealer required diagnostic test approval from manufacturer before proceeding in one case; vehicle was not repaired.
Recalls/TSBs owners mention: Manufacturer required diagnostic test before repair authorization; dealer awaited manufacturer approval
Timing cover oil leak
Oil leaking from timing belt cover gasket, a known design issue affecting multiple Toyota models including Avalon.
When: 36k–38k miles on vehicle
Symptoms owners cite: Visible oil leak while parked; Oil leaking from timing cover area
Repairs/costs cited: Quoted repair cost $1,500–$1,900; labor comprises bulk of cost; replacement part itself inexpensive. TSB EG049-07 issued in 2007. One owner reports $1,900 estimate to replace gasket and water pump.
Recalls/TSBs owners mention: TSB EG049-07 issued in 2007 for this condition
A/C compressor mounting bolts corrosion
Bolts holding clutch assembly to A/C compressor rusting severely, posing risk of compressor separation and secondary damage during driving.
When: Noticed at ~24k miles; worsening by 38k miles
Symptoms owners cite: Severe rust on compressor mounting bolts; Bolt heads nearly disintegrated; Secondary rusting on clutch assembly component; Risk of compressor coming apart during operation
Repairs/costs cited: Not repaired under warranty per owner
Recalls/TSBs owners mention: Manufacturer refused warranty coverage
Exhaust fume recirculation through cabin
Exhaust odor being pulled into vehicle cabin when rear window is cracked, triggered by automatic air recirculation activation.
When: Timing not specified
Symptoms owners cite: Exhaust smell entering cabin when rear window opened; Air recirculation mode automatically engaging; Fumes present despite setting air flow to fresh air; Child experiencing choking from fume exposure
Stuck accelerator pedal
Accelerator pedal sticking in open position during high-throttle driving situations, continuing acceleration without driver input.
When: During highway merge and passing maneuvers
Symptoms owners cite: Pedal stuck in open position during acceleration; Vehicle continuing to accelerate uncontrollably; Brake pedal initially ineffective; Pedal returning to normal after stomping with right foot
Engine mount weld failure and radiator fan contact
Broken motor mount weld causing engine movement; radiator fan hitting shroud, creating fire hazard. Vehicle lurches forward at stops.
When: Timing not specified
Symptoms owners cite: Vehicle jumping forward at traffic lights or when stopped in gear with brake applied; Radiator fan hitting shroud; Broken weld on motor mount
Repairs/costs cited: Dealer unable to address issue per owner report
Synthesized from 10 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 2006 Toyota 4Runner?
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 2006 Toyota 4Runner?
It's a documented issue but not catastrophic. 10 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?
Based on the 10 complaints filed, engine issues most often appear around 61,015 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/2006/Toyota/4Runner.
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.