The difficulty is not having th engine lamp off prior to the promlem begining, however, when the lamp blinks it's an indication that there is a missfire occuring, severe enough to cause catalyst damage. I suspect you may have an ignition problem, as this is the most common cause of a missfire such as this one. It might be occuring on one cylinder, or more than one. If you havn't had a tune up (plugs, wires, cap, rotor, fuel filter) this would be a good start, since they're the most common reason for causing a missfire and if these parts are bad already, they will have to be relaced anyhow to continue locating the problem. Now, you should get the check engine lamp looked at, it will tell us which cylinder exactly is causing the missfire, or if it's more than one cylinder; also we can find out what reason kept the lamp on before. If the lamp is operational, and it will have to be if your state has any emmisions testing, than you will be able to correctly tell if something isn't right.
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