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.
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Repairpal verified 1991 Toyota Previa problems
The timing chain can develop a rattling noise caused by failing timing chain guides. This is often due to extended mileage intervals between oil changes that allows the oil to become dirty and abrasive which wears away the timing chain guides until they fail. The timing chain and guides should be inspected at each valve adjustment, otherwise serious engine damage may result.
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.
Usually by 150,000 miles the AC system will need some attention, especially in climates where it is used often. Our technicians tell us that it is best to service the AC system every 2-3 years. This keeps the moisture in the system at a minimum which extends the life of the components.
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.