1998 Toyota Supra Problems

RepairPal has identified the most common problems with the 1998 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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20
Known Problems

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.

At higher mileages (125,000+) the Engine Coolant Temperature Sensor may intermittently stop working, especially when the vehicle is fully warmed up. This can cause the engine to stall unexpectedly.

At 125,000-150,000 miles, the Brake Master Cylinder may need replacing. It is critical to adjust the brake pedal to Master Cylinder pushrod clearance or the brakes will drag and over heat.

The Throttle Position Sensor can get out of adjustment due to wear in the throttle body or due to carbon build up. This will cause the idle timing to advance more than 30 degrees which will cause very high HC and NOx emissions. Conversely, the Throttle Position Sensors can wear out and not properly advance the timing which causes a lack of power and poor fuel economy.

A rough idle and even an emissions inspection failure for high HC and CO can be caused by improperly adjusted valves. Also, exhaust valves may become to tight which can lead to valve failures. Our technicians tell us that regular valve adjustment inspections are a must.

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.

It is important to regularly check the valve clearance as the exhaust valves may become too tight. This will lead to valve failures which are expensive to repair.

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

The Evaporative system may have problems with the vapor canister releasing charcoal pellets that plug the vent valve. Typically a Code P0441, P0442 and P0446 will be set. The key code is the P0446 which is a vent valve electrical failure. The proper repair is to replace the entire canister with all the valves as a unit. This is located on top of the fuel tank and is expensive. Our Technicians tell us that for awhile Toyota was covering these problems, but this may have changed. It would not hurt to call the dealer if this problem occurs to see if Toyota is still helping with these repairs.

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.

 

At higher mileages (125,000+) the mass air flow sensor may cause the vehicle to idle rough, run rich and even stall. Our technicians recommended to replace the Mass Air Flow Sensor with a factory unit because the aftermarket units have very mixed results.

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.