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Random motor shutdown

My 1998 Toyota Avalon motor randomly shuts down, yet the electrical system remains operable, e.g., radio, lights, panel, wipers, etc. Toyota is baffled, having checked all onboard monitors with no indication of malfunctions.

Anybody have any ideas or suggestions? It’s scary when it happens while on the freeway at 65 mph. One has to shift to neutral and restart the car, which it has restarted so far each time.

I can’t in good conscious sell the car with this serious exposure, so junking it seems the only alternative.

This can be a defect in the ignition switch, a problem in the engine immobilization system, or a bad engine management computer. No need to junk the car.

Until you find the problem you may want to try restarting the motor while the car is coasting. You didn’t say if you shift to neutral while moving or if you pull off onto the shoulder.

If the engine stumbles and stalls, it’s likely a fuel problem…that is, fuel being injected into the engine. Lack of fuel should affect restart.
If the engine stalls suddenly, the cause is likely a sudden loss of spark; which can be a temporary loss of electrical power (or, instructions) to the spark producing components.
There is a test module which can monitor fuel, electric power, and fuel injection and report when one fails (temporarily, or not). Since no one admits to having this monitoring module, it’s not much use to look there for a solution.
Some suspects for sudden stalls: the relay which powers the engine computer and/or powers fuel injection or spark; the ignition switch (NOT, the ignition lock); some sensor, such as a crankshaft sensor; ignition module or igniter.

How much time did “Toyota” spend looking for the cause of the problem before they claimed they are “baffled” (not how long they had the car,how much time did they spend actually looking for the cause)? Did you put a halt to the search (due to cost) or did Toyota ask you to take the car away?

I ask this because if the right man spends enough time a answer will be the result.