The Toyota Previa is a popular model of minivan. The 1991 Previa was the debut year in the United States. In 1997, it was replaced by the Toyota Sienna. The Previa's mid-engine design placed access to the engine under the front seats of the van. This proved to be one drawback in the sale of this vehicle, as it is an unusual location for an engine. Troubleshooting the common problems with a 1991 Toyota Previa involve the typical ones associated with any 20-year old vehicle, plus a few that seem to plague this particular model.
Check the energy flow of your 1991 Previa. The energy flow starts with the battery, and travels to the alternator which replenishes the battery with power to prevent it from dying quickly. From the alternator, the energy flows to the spark plugs and distributor, supplying electrical power to the Previa. Check the wires from the battery and to the spark plugs for wear. Check the spark plugs for carbon scoring or black marks that may indicate they are faulty. If the Previa is not starting, it could be any one of these items.
Check the fuel flow. The fuel filter keeps debris and other particles in gasoline out of the engine. Check the fuel filter, and replace if necessary. From the filter, the fuel is pulled or pushed into the engine compartment by the fuel pump. Check the fuel pump for frayed hoses or disconnected electrical wiring. From the fuel pump the gas is sent into the carburettor, or electronic fuel injection system, and mixed with the air flow to generate the "explosion" necessary to start the engine. Sometimes fuel lines can leak or become separated from their connections.
Check the air flow. Without air, the fuel will not combust and start the engine. The air flow begins with the air intake manifold. Your air filter keeps debris out of the air flow system. If the air filter appears dark or is clogged, replace it immediately. The air flows into the carburettor or electronic fuel injection discussed earlier. Check the intake manifold for holes in the plastic covering.
Check the exhaust manifold for blockages in the tailpipe or muffler. Any debris or blockage that interferes with the flow of air into or out of the vehicle can prevent the Previa from starting or cause hesitation when running.
Open the rear door of the Previa van. Inspect the small hydraulic rods on the sides. They should be attached firmly to the door and the frame. The 1991 Previa rear door is heavy, and when these rods fail the rear door will not stay up. It is a common problem with the Previa, but the rods can be easily replaced.
Check the cold start injector. On cold days it supplies additional fuel when the engine coolant is lower than 30 degrees Celsius. If you only seem to be having trouble starting the Previa on cold days, this may be your problem. Replace the injector if needed.
Check all the sensors by plugging the vehicle up to a diagnostic machine. Previa owners have reported issues with the air flow sensors and the engine coolant temperature sensors. If the air flow sensor fails you won't know when there is difficulty with the intake or exhaust manifolds. Without the engine coolant sensor, it is likely that the Previa will overheat.