Q: Rough idling but car runs normal at high speeds. One plug cylinder well has oil seepage.

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My vehicle idling suddenly is rough and lower than the 1000 rpm but runs normal at higher speeds. Rough idle when stationary. Oil seepage in one spark plug well. Seems valve cover gasket needs to replaced. Is a change of spark plugs in order or a complete tune up and gasket change?

My car has 190000 miles.
My car has a manual transmission.

The rough idle may be caused by many different things such as low fuel pressure, low voltage to the fuel injectors, dirty fuel injectors, a vacuum leak, a faulty Oxygen sensor or a dirty, or failing idle air control valve. Any of these possibilities relate to fuel delivery issues that will disrupt the normally balanced air/fuel mixture that would otherwise allow the motor to run smoothly. Dirty or failing spark plugs or wires may also cause a rough idle if they are causing one or more cylinders to misfire. I would recommend having an expert from YourMechanic come to your location to diagnose your rough idle problem.

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