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I just got my 2015 Civic back from the shop for a rough idle, and they replaced the spark plugs and cleaned the throttle body. It’s better, but the engine still feels a bit shaky when I’m stopped at a light, and I’m not sure what to check next. Could it be something like a motor mount starting to go, or maybe they missed an issue with an ignition coil?

I had a similar rough idle after a plug change. I started by checking for vacuum leaks around the intake. A loose hose clamp here and a small crack there and the idle got calmer, though it wasn't perfect.

My first hunch was ignition too, so I watched misfire data. A shop scan finally showed a weak spark on one cylinder. Replacing the coil fixed a chunk of the shake.

I also thought about motor mounts. At a stop the engine wobble can feel like mounts are going soft, but it's hard to tell without lifting the car. Mine seemed okay but one mount looked a little soft on inspection.

Is it worth having the idle air control valve tested?

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