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MOTRS

Supra (A70)

1986-1993 / Coupe / Japan

All Supra (A70) problems All workshop issues
Minor Electrical

Engine Wiring Harness Degradation

Symptoms

Intermittent electrical faults, random misfires, fluctuating idle, gauge malfunctions, check engine lights with inconsistent fault codes.

Cause

After 30+ years, the factory wiring harness insulation becomes brittle, particularly in the engine bay where it's exposed to heat. Connectors corrode internally. On modified cars, spliced wiring from previous owners adds further failure points.

Fix

For a stock car, carefully inspect the harness, repair damaged sections, and clean all connectors with contact cleaner.

Apply dielectric grease to connectors after cleaning.

For modified cars with extensive wiring issues, a complete aftermarket engine harness from a specialist (e.g., Wiring Specialties) is the definitive solution ($500-1,500 for the harness, plus installation).

Cost mentioned in fix
$500-1,500 for the harness

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Other known issues

Common Electrical

ABS Module Failure

The ABS warning light illuminates permanently. The ABS system may activate inappropriately (pulsing brake pedal during normal braking) or not function at all.
Common Electrical

Power Steering Pump Whine

A persistent whining noise from the power steering pump, most noticeable at idle with the steering wheel centred (no load on the system).
Common Engine, 7M-GTE (Turbo)

Head Gasket Failure

The head gasket blows, allowing coolant into the combustion chambers and/or oil passages. White smoke from the exhaust, coolant loss without visible external leak, overheating under boost, milky oil on the filler cap, and bubbles in the coolant overflow tank. In severe cases, hydrolock (coolant filling a cylinder and bending a connecting rod on startup).
Critical Engine, 7M-GTE (Turbo)

Low Oil Pressure at Idle

Oil pressure drops below 10 psi at hot idle. The factory oil pressure warning light may flicker or illuminate at idle, particularly in traffic on hot days. The engine may develop bearing noise (deep knocking from the bottom end).
Common Engine, 7M-GTE (Turbo)

CT-26 Turbo Failure

Loss of boost pressure, excessive oil smoke (blue/grey) on startup or deceleration, whistling or grinding noises from the turbo, and oil in the intercooler piping.
Critical Engine, 7M-GTE (Turbo)

Cooling System Inadequacy Under Boost

Coolant temperature climbs rapidly under sustained boost, particularly in traffic or on hot days. The temperature gauge sits higher than normal and doesn't recover quickly.
View all 17 Supra (A70) problems