Reader Question: Hello Austin,
I just purchased a used 2000 Honda Civic Ex with 35,000 miles. It is idling a little roughly. Previous owners said nothing needed to be done. However, when I changed the oil, the air filter was very dirty so I changed that.
What about changing the spark plugs? Would that help the idling?
Anything else you would recommend.
You really need to determine if this roughness felt at idle is due to an engine performance problem like dirty spark plugs or a dirty throttle body or is this mechanical vibration from worn or broken motor and transmission mounts.
Since this vehicle is 7 years old, there is a good possibility that the engine mounts are a little worn and causing the engine to vibrate.
With the hood up and the engine running, I would get someone to look at the engine and the engine mounts as you run through the gears (with your foot on the brake and the emergency brake on) selecting park, drive, reverse, neutral and few times slowly. You are looking for excessive up and down movement in the engine as you select gears.
These small cars are very finicky when it comes to the slightest wear in a rubber engine mount, a vibration inside the car can be felt.
If the engine mounts appear to be ok, you might also want to inspect the following:
1. Clean the throttle body – this is where the fresh air hose from the air cleaner attaches to the engine (like where the carburetor would be if it had one).
2. Check spark plugs and spark plug wires.
3. Check base idle speed and increase speed if needed – bring up the idle speed just a little bit can help mask vibration caused by worn engine mounts.
4. Clean the fuel injectors.