Been a mechanic for 20 yrs I all good up to 2003 or so.I know the ignition switch doesn't start the car, it is just a signal to the ecm too start the car.Ecm actually actuate starter. If I drive to the store maybe 10min and park, come back out and try to start car ecm engages starter for its cycle but engine won't start. It will start on the second time and idle will go up and down from300 rpm to 700rpm. It will do this for 30 to 60 sec. Or if I put my foot on the gas pedal. Plugs are good, ignition coil pack is good, fuel filter is good.If car is cold, no problem. If car sits for half hr or more no problem.

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