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General Smog Check

Check Engine Light On - 1998 Ford Taurus. 3.0 Liter Engine - Misfire P0301 Trouble Code.

I had a trouble code scan done. Came up with P0301 Misfire in cylinder one. I replaced the spark plugs and my Ford Taurus runs better now but the Check Engine light is still on. Smog station will not smog test my car. Any advice?


First question I have is... Did you reset the Check Engine light by clearing

the trouble codes? Second question... Does your Ford Taurus's check engine

light re-illuminate after a reset soon as you start the engine? Have you

rescanned the OBD II for new trouble codes; or perhaps the same trouble code

(P0301) reappearing?


If the Check Engine light turns on again after resetting and you have

insured the engine ignition system is working properly, you may want to run

the ignition system on an ignition oscilloscope. The oscilloscope will show

small variances in the ignition pattern which might not be apparent to you

by simply listening to the engine or feeling for misfires.


If the oscilloscope shows no ignition system defects either, the next

component you might want to suspect is your Ford Taurus's camshaft position

sensor. Why the camshaft position sensor? Believe it or not, the way your

Ford's OBD II system learns about a misfire or senses a misfire is by the

"skip in the beat" seen by the Camshaft Sensor at the exact moment the

misfire occurs. So if all else fails and you can't get rid of the Misfire

Trouble code, your Ford might not have a misfire at all and just a faulty

Camshaft position sensor.

posted by SmogTips Support 10-04-2010 02:07 PM