What are the most common Toyota 4Runner problems?
According to Au7o's research across NHTSA recalls, manufacturer TSBs, and owner forum reports, the 1999 Toyota 4Runner has 11 documented issues. The most frequently reported are: Rocker Panel, Rear Wheel-Arch and Pinch-Weld Rust, Front Lower Ball Joint Wear and Separation (3rd Gen), Catalytic Converter Efficiency Below Threshold (P0420 / P0430) — Aging or Manifold-Integrated Cats. Of these, 2 are rated critical and should be addressed promptly.
Is the Toyota 4Runner reliable?
The 1999 Toyota 4Runner has 11 known issues compiled from NHTSA recalls, manufacturer TSBs, and owner forum reports. 2 issues are rated critical: Rocker Panel, Rear Wheel-Arch and Pinch-Weld Rust and Front Lower Ball Joint Wear and Separation (3rd Gen). Prospective buyers should inspect for these issues and factor potential repair costs into their purchase decision. Regular maintenance following the manufacturer's schedule helps prevent many common problems.
How much does it cost to fix common Toyota 4Runner problems?
Repair costs for known Toyota 4Runner issues range from $15 to $3,500, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, Rocker Panel, Rear Wheel-Arch and Pinch-Weld Rust, typically costs $600-$3,500 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.
What is the 1990-1999 Toyota 4Runner Rocker Panel, Rear Wheel-Arch and Pinch-Weld Rust?
1990s 4Runners are structurally durable but very prone to age- and salt-driven body rust, especially at the rocker panels, lower quarter/rear wheel arches, and the pinch-weld seams. On 3rd-gen trucks (1996-1999) the factory sunroof drain lines route into the rocker cavities, and… Repairs typically run $600-$3,500. Severity: high.
What is the 1996-1999 Toyota 4Runner Front Lower Ball Joint Wear and Separation (3rd Gen)?
The front lower ball joints on 3rd-generation 4Runners (1996-1999, sharing the same part through 2002) wear out and, in worst cases, separate from the steering knuckle, causing loss of steering control and front-corner collapse. Toyota issued a formal safety recall/Special Servic… Repairs typically run $400-$950. Severity: high.
What is the 1999-2009 Toyota 4Runner Catalytic Converter Efficiency Below Threshold (P0420 / P0430) — Aging or Manifold-Integrated Cats?
As 4Runners accumulate miles, the catalytic converter loses efficiency and the ECU sets P0420 (Bank 1) and/or P0430 (Bank 2) when the downstream O2 sensor starts to mirror the upstream sensor. On the 4th-gen 1GR-FE, the primary cats are integrated into the exhaust manifolds, whic… Repairs typically run $150-$2,500. Severity: medium.
What is the 1996-2002 Toyota 4Runner 3.4L 5VZ-FE Knock Sensor & Sub-Harness Failure (P0325/P0330) — Brittle Harness Under Intake?
On the 3rd-gen 4Runner's 3.4L 5VZ-FE V6, the two knock sensors sit in the engine valley beneath the upper and lower intake manifolds, and their sub-wiring harness bakes over time. The harness insulation becomes brittle and crumbles, opening the circuit and setting P0325 (knock se… Repairs typically run $150-$900. Severity: medium.
What is the 1996-2009 Toyota 4Runner Power Steering Pump / System Leak & Whine — Reservoir Screen Clog and Seal Failure?
3rd- and 4th-gen 4Runners commonly develop power-steering whine and reddish ATF leaks with age. A whine is often not the pump itself but old fluid or a clogged filter screen in the bottom of the PS reservoir; leaks frequently originate at the union-bolt gaskets, high-pressure/ret… Repairs typically run $20-$500. Severity: medium.
What is the 1990-1999 Toyota 4Runner Timing-Belt-Driven Water Pump Leak and Overheating (V6)?
Both V6 4Runners (3.0L 3VZ-E and 3.4L 5VZ-FE) use a water pump that is driven by, and buried behind, the timing belt. The pump's seal weeps coolant with age/mileage, and because it sits behind the timing cover the leak is easy to miss until the truck overheats or drips coolant fr… Repairs typically run $600-$1,200. Severity: medium.
What is the 1990-1999 Toyota 4Runner 4WD Won't Engage — ADD (Automatic Disconnecting Differential) Vacuum Actuator Failure?
4WD-equipped 4Runners use an Automatic Disconnecting Differential: a vacuum-operated actuator on the front differential slides a collar to couple the passenger-side front axle when 4WD is selected. With age the vacuum supply hoses crack, the vacuum switching valve/solenoid or the… Repairs typically run $150-$650. Severity: medium.
What is the 1996-2002 Toyota 4Runner 3.4L 5VZ-FE Water Pump Weep Leak — Replace With Timing Belt Service?
The 5VZ-FE water pump is driven off, and buried behind, the timing belt. Its shaft seal wears with age and mileage and coolant begins seeping from the pump's weep hole — the designed early-warning drip before the bearing fails. Because accessing the pump requires the same teardow… Repairs typically run $150-$900. Severity: medium.
What is the 1996-2009 Toyota 4Runner EVAP System Leak — Charcoal Canister / Vacuum Switching Valve (VSV) Failure (P0440 / P0441 / P0446)?
EVAP faults (P0440 general malfunction, P0441 incorrect purge flow, P0446 vent control circuit) are among the most common check-engine codes on 3rd- and 4th-gen 4Runners. Toyota issued service bulletin EG013-03 covering these codes across 4Runner/Camry/Tacoma. The frequent culpri… Repairs typically run $15-$500. Severity: low.
What is the 1996-1999 Toyota 4Runner P0401 EGR Insufficient Flow — Clogged EGR Passages (5VZ-FE)?
OBD-II 3rd-gen V6 4Runners (1996-1999, 3.4L 5VZ-FE) very commonly set code P0401 (EGR insufficient flow) as they age. The recirculated exhaust and the narrow EGR tube/passages coke up with carbon over the years, so even a working EGR valve can't flow enough gas, and the vacuum-mo… Repairs typically run $120-$500. Severity: low.
What is the 1996-2002 Toyota 4Runner 3.4L 5VZ-FE Idle Air Control (IAC) Valve Carbon Fouling — Rough/Surging Idle, Stalling (P0505)?
The 3.4L 5VZ-FE uses a rotary-solenoid Idle Air Control (IAC) valve on the throttle body to manage idle. Over high mileage the IAC passages and valve clog with carbon and oil deposits, producing erratic idle (hunting between ~700 and ~1200 RPM), high idle, or low idle that shakes… Repairs typically run $20-$350. Severity: low.
