Q: Q: Idle rough

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Engine will run good for a while. Then idle rough when shut off it will be hard to start. When idle smooth its ready to start. Last time idle rough check engine light came on. I cont to drive. It smoothed out little while later then dtc. Light goes out and idle smooth again. When idle rough. Turn on Ac and engine 95% smooth out

My car has 175000 miles.
My car has an automatic transmission.

There are a number of things that may cause a rough idle. A rough idle may be caused by things such as low fuel pressure, low voltage to the fuel injectors, dirty fuel injectors, a vacuum leak, a faulty Oxygen sensor, dirty or failing idle air control valve, a faulty camshaft or crankshaft sensor, faulty spark plugs or wires ad many other things. Any of these possibilities may relate to fuel or spark problems that will disrupt the normal combustion process that would otherwise allow the motor to run smoothly. You may notice the motor running a bit rough or shaking if any of these components are not functioning as they should. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

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