spark plug condition and engine misfire
 

it cost $261 to diagnose engine error light and perform engine tune up.
The spark plugs were the most economical choice at the parts store.
they lasted less than 30,000 miles and the engine light came on. engine misfire was the error code. the diagnostic took an hour and fifteen minutes. the only conclusion was the spark plugs( not the coil packs ).
a tune up and throttle body cleaning was performed and took another hour to perform. the car was restarted and the error code cleared.

if you replace your own spark plugs and use quality parts you will avoid my sad story.
:(

What about the plug wires? I had a similar diagnosis, and it turned out one of the new wires was bad. Free replacement.

very helpful for the most of engine diagnosis. coz plug is the only device most of time that fails..