engine light came on and thenn went off and is now back on...?

It is possible the repair shop saw the light on, did the work you specified, then cleared your error codes as a courtesy...I'd check with them to see if they even read the codes to isolate the problem. If not, have the codes read at a good shop, then repair the affected system...without the codes or without more detail on exactly "what" it does "when", it is hard to narrow down the cause of the problem.

It could be something as simple as a fuel filter, spark plugs or the plug wires...or you could have fuell pressure issues...

One thing that even experienced mechanics can forget to check is all the little rubber vacuum hoses under the hood. One or more coud be cracked, broken, or simply fell off it's connector, causing excess air to be sucked into the intake manifold. THAT will cause an engine to run rough at idle and slower speeds. It will also cause very bad gas mileage too, and is the very cheapest of problems to repair...

Hope that helps you out...

i am a mechanic and i think that it may have some dirty fuel injectors take it to your local repair shop and they should have a computer to connect to your car that tells you whats wrong with your car well thats at least what we do when a car comes in with the engine light on