1998 Toyota MR2 Problems: 7 Known Issues

On the 1990-1999 Toyota MR2, the SW20 body rusts in predictable, structurally important places. Sound-deadening foam packed into the rear quarters behind the seats traps moisture and rots the rear sills from the inside. The rear wheel arches and inner arches corrode, especially where road salt isn't washed off. The stiffening/brace bars under the car near the engine bay are so rust-prone from poor factory paint coverage that the community nicknamed them 'cancer bars.' The rear subframe/crossmember also corrodes. Because these are load-bearing areas, corrosion here hits both safety and resale value hard, and repairs can be expensive welding jobs. This is a top three pre-purchase priority alongside turbo and cooling-system health.

On the 1990-1999 Toyota MR2, two age-related annoyances plague SW20s. First, on glass T-bar (T-top) cars the roof seals leak with age: the rubber shrinks and hardens, so the seals on the body and the T-top panels pull apart at the vertical join near the door-glass opening, letting water into the cabin (which in turn feeds the rear-sill rust problem). Documented leak points include the rear of the T-bar, the front of the T-bar, and the A-pillar seal. OEM replacement seals are available but expensive and fiddly to fit correctly. Second, the pop-up headlights are raised by small electric motors that fail with age; a very common specific cause is an open diode in the motor's limit-switch circuit, leaving a headlight stuck up or down. Both are classic buyer's-guide checkpoints.

On the 1990-1999 Toyota MR2 3S-GTE (2.0L turbo), the turbocharged 3S-GTE is prone to head gasket failure, particularly on cars run at elevated boost or with a neglected cooling system. The engine's design works against it: narrow head-gasket 'lands' around the combustion chambers, large coolant jackets, a factory paper/composite gasket, and torque-to-yield (TTY) head bolts that stretch over time. Heat, age, and boost combine to let combustion pressure breach the gasket. A very common real-world pattern is a car that idles and cruises around town at a perfect temperature but blows coolant out the overflow and overheats during sustained hard boost. The naturally-aspirated 5S-FE and 3S-GE are far less affected; this is chiefly a turbo (3S-GTE) failure mode, though any SW20 with 25+ years of unknown history is a candidate.

On the 1990-1999 Toyota MR2, sW20s drip oil from several age-related seals: the valve/cam cover gasket, the distributor O-ring and housing, the front cam seals, and the oil-pump shaft seal and housing O-ring. On its own this is a nuisance, but the tight mid-engine bay makes it consequential: oil that runs down onto the alternator (mounted low, in the path of front-seal and distributor leaks) can foul and kill it. In a documented worst case, a distributor leaking badly enough internally can short the alternator and blow the OEM voltage regulator in the trunk. Replacing an oil-soaked alternator in the cramped SW20 bay is a genuinely unpleasant job, so the small leaks are worth chasing before they cascade.

On the 1990-1999 Toyota MR2, the second-generation MR2 (SW20, 1990-1999) is well-known for snap oversteer, particularly during mid-corner lift-off or abrupt throttle changes. The mid-engine layout with short wheelbase and rear weight bias causes the rear end to break loose suddenly when weight transfers forward during deceleration. Toyota revised the rear suspension geometry in 1993 (Rev 2) and again in 1994 (Rev 3) to improve predictability, but the inherent characteristic remains. Proper driving technique is essential.

On the 1990-1999 Toyota MR2, because the SW20 is mid-engined with the radiator up front, coolant travels the full length of the car through long metal pipes running under the floor. These pipes, plus the bypass line and the water neck/filler-neck assembly, corrode from the inside out. The system mixes many dissimilar metals in contact with coolant (steel, stainless, aluminum, copper, brass, cast iron), which sets up galvanic/electrolytic corrosion so the more-reactive metal is sacrificed. Old or unchanged coolant loses its corrosion inhibitors and accelerates the process. Rust flakes can break off internally and circulate through the cooling system, and pinholes/perforation eventually cause coolant loss and overheating, which then endangers the head gasket. This affects all SW20 variants and is a top pre-purchase inspection item.

On the 1990-1999 Toyota MR2, the SW20's ignition igniter (ignition control module) and distributor pickup are recognized failure points, especially intermittently and when hot. The igniter is fed the IGT signal from the ECU and switches the coil; the distributor houses the pickup that tells the ECU the engine is turning. When the igniter fails it often does so without setting a code, and typically acts up once the engine is hot-soaked, producing intermittent or total loss of spark and stalling/no-start. Related no-spark causes on these cars include the coil, distributor pickup, corroded/loose connectors and grounds at the igniter/coil/distributor, and (less often) wiring. Because failures are intermittent and code-free, they are frequently misdiagnosed.