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I had a misfire in a 2008 Toyota Corolla this week that occurred four times (for a few seconds each time ) in 150kms. It made the car shudder and jerk, especially if it was pulling up hill. The anti skid light and the engine light came on and on one occasion many of the other dash warning lights came on and the LCD display reset itself, very much like the ignition had just been turned on. The car has a Toyota warranty so I took it to the local Toyota dealership who plugged in their diagnostic box and found a few codes up . The first being a failed coil. Evidently this fault also impacted on the other ECUs and brought up other codes which did not make much sense.
The dealership reset the main ECU and suggested we try again rather than test the coils as they suggest that would not show up anything. This does not fill me with confidence as it is quite alarming when this happens in the middle of Auckland traffic.
Surely they should at least get the coils tested in the hope of finding a weak one. Is there anything else that should be done in this circumstance?. They will not replace all the coils because of cost. Surely a fault like this should be remedied straight away under warranty rather than heading into the traffic to make it fault again knowing it will do exactly the same thing. What will they know more next time?

The fault codes stored in the computers are there to guide the mechanic but will not necessarily pinpoint the fault. For a misfire situation you would expect the dealer to at least test the coils which is the most common cause of a misfire. It could be a number of things causing the problem like an electrical fault, injection computer, fuel injectors, etc but it will not fix itself and it is highly likely that the same fault codes will appear when this happens again so they will be no closer to solving the problem.
It is possible that the dealer didn’t have the time on the day to do a full diagnostic and for this reason you should book the vehicle in to the service centre and if possible for a few days as it might not be as easy as replacing a coil to fix the fault.

Thanks for the reply. The fault occurred again this week so the car was booked in for a complete check. They found the same coil misfire codes but because the code did not tell them which one Toyota will not replace until they find the faulty one. They checked the resistance of each coil but did not test them. So they changed the plugs( at my cost) as a first step, just in case a plug is faulty . It certainly does not fault like a bad plug and pulls strongly up hills and under load. So It is back into the traffic to fault again with the goal of it faulting completely! Not a realistic or safe call particularly if you are passing large truck with traffic behind you when it faults. I did ask why they did not install at least one new coil and then I could work through the coils each time it faults. We might strike it first or second time.
It is a bit frustrating being bound by a Toyota Warranty that prevents me taking that action myself.