1990 Toyota Supra Problems

RepairPal has identified the most common problems with the 1990 Toyota Supra as reported by actual vehicle owners. We'll tell you what the problem is and what it'll take to fix it.

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16
Known Problems

The Toyota Supra and Supra Turbo from 1986-1992 (MKIII) is known to leak engine coolant and overheat due to a leaky heater control valve. Drivers will notice a decrease in heater performance, and increase in engine temperature. 

The purpose of this valve is to control the amount of heat that enters the cabin of the vehicle. If this valve has failed, it is recommended to use the OEM part for replacement.

Please note, the engine in both versions of the 1986-1992 Supra is prone to head gasket failure, so it is imperative that any coolant issues are addressed immediately to avoid costly repairs.

The third-generation (MKIII) Toyota Supra has a common problem with the rear hatch leaking water into the vehicle.

Through normal operation, dirt, leaves, or twigs will build up between the hatch and the body causing the hatch seal to deteriorate at a rapid pace. As the problem worsens, the hatch will develop water leaks, and wind noise in the rear of the car will increase. If this issue goes unchecked, rust will begin to develop in the spare tire compartment, and around hatch.

The solution is to replace the rear hatch seal, and thoroughly clean and wax the body where the seal makes contact. If rusting has already begun, the body will require repair.

To help prevent the issue, frequently clean any debris build-up between the hatch and body.

The 1986-1992 Toyota Supra and Toyota Supra Turbo may lose power, fuel economy, and possibly have black smoke from the tail pipe due to a known issue with the knock sensor and/or knock sensor wiring harness. 

The knock sensor is mounted to the engine, and detects knocking and pinging conditions which may harm the engine. When the knock sensor malfunctions, engine performance is decreased and fuel consumption is increased causing 'rich' running conditions. The check engine light is associated with OBD Trouble Code 52.

There are two common fixes for this issue: Inspect/repair sensor wiring harness, and test/replace knock sensor.

The 1986-1992 Toyota Supra and Toyota Supra Turbo used an asbestos type head gasket which commonly fails. Symptoms of a blown head gasket include:

-Start and stall, or no start condition

-Rough idle if the engine starts

-White smoke from exhaust

-Loss of power

-Milky, white oil on dipstick 

If you experience these symptoms, do not attempt to restart the vehicle, and have the problem addressed immediately. 

The solution is to replace the head gasket with an updated metal head gasket, and flush the engine and coolant systems of contaminants. 

The 1986-1992 Toyota Supra and Toyota Supra Turbo used an asbestos type head gasket which commonly fails. Symptoms of a blown head gasket include:

-Start and stall, or no start condition

-Rough idle if the engine starts

-White smoke from exhaust

-Loss of power

-Milky, white oil on dipstick 

If you experience these symptoms, do not attempt to restart the vehicle, and have the problem addressed immediately. 

The solution is to replace the head gasket with an updated metal head gasket, and flush the engine and coolant systems of contaminants. 

The power steering pump and power steering hoses tend to develop leaks and may require replacement.

The EGR System tends to get restricted or blocked with carbon after 100,000- 125,000 miles which will cause an emissions test failure for NOX. If the EGR system is equipped with an EGR temperature sensor it will trigger a Check Engine Light for improper EGR flow. The repair is to clean out the EGR passages and the EGR Temperature sensor. Our technicians tell this repair is pretty straight forward and takes about 1-1.5 hours. It is also wise to verify the EGR system components i.e. the Transducer, EGR Valve and VSV Solenoid at this time.

Over the time the exhaust gas recirculation (EGR) system may become plugged with debris, the oxygen sensor may also be getting slow or 'lazy' around this time. When servicing or cleaning  the EGR system, it is a good idea to replace the oxygen sensor because it works in tandem with the EGR system.

At higher mileages, (125,000-150,000) the automatic transmission may not shift correctly. This can be caused by the throttle position sensor being out of adjustment or a shift solenoid needing to be replaced. Typically the transmission does not need to be completely overhauled.

If the vehicle will not crank over, the most common problem is the starter, which tend to fail at about 100,00-125,000 miles. Sometimes it is only the starter solenoid contacts, but often the complete starter (including solenoid) needs to be replaced.

Our technicians report that by 100,000 miles, the ignition key tends to wear out and should be replaced or it may not work as well in the door locks or ignition lock cylinder.

Brake fluid can become dirty and may cause problems in the brake system; it should be flushed every 60,000 miles.

As the size of the Supra vehicle gets ever larger, there is a tendency to warp the front rotors. This will be felt as a shudder in the steering wheel when braking. The front rotors can be remachined, if there is sufficient material left, otherwise the front rotors will need to be replaced. It is recommended to use factory quality rotors because cheap quality rotors warp very easily and tend to squeak and squeal.

At higher mileages, an anti-lock brake system wheel speed sensor may wear out and illuminate the ABS warning light. It is recommended to replace the sensor with a factory part and be sure to clean all rust and debris from the mounting area because the mounting distance is critical. Failure to do so may result in the new sensor setting false trouble codes. Be sure to check the condition and runout of the front wheel bearings on the 2WD and 4WD vehicles and the CV joints on the 4WD vehicles since worn wheel bearings and/or CV joints can cause the ABS trigger rings to rub against the ABS sensors and damage them.

 

Our technicians tell us that it is important to change the coolant with factory coolant and replace the thermostat every 60,000 miles. This will help to protect the head gasket, otherwise the head gasket can deteriorate and be stressed to the point of failure.