check engine code po303

Question

Mine is Isuzu Trooper.
When the weather is relatively cold (around 50 degrees, but not always), the car starts rough, displaying CHECK ENGINE light, occasionally flashing, othertimes without flashing. The flashing changes to steady when I restart the engine. The steady light sometimes disappears after some driving or next morning.
I had the same problem last winter and have all 6 spark plugs replaced (really?) at a cost of nearly $300 at a local service station.

Answer 1

HI there,

This misfire could also be the result of a bad ignition coil, or a problem with one of the fuel injectors.