How to Troubleshoot a Rough Idle on a Nissan Altima

by Kelly Reese

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A rough idle on a Nissan Altima can indicate that you need to change your spark plugs or you need to check your distributor cap. The spark plugs bridge a gap between two electrodes in the engine that allows fuel to be transported to the engine by the ignition of a spark from the spark plug. A distributor routes voltage from the ignition coil to the spark plugs. The distributor connects to the top of the distributor and contains a terminal that connects to the ignition coil. A damaged spark plug or distributor cap will cause your Altima to have a rough idle or not start at all. You can replace and clean them yourself.

Clean the Distributor Cap

Step 1

Push the gear lever in "Park." Locate the lever labeled "Hood" under the steering wheel column. Pull the lever towards you. Walk to the front of the vehicle and open the hood.

Step 2

Locate the silver engine block in the center of the Altima. Follow the four black hoses coming from the top of the engine. The hoses connect to the distributor cap.

Step 3

Locate the two screws on the left and right side of the distributor cap. Remove the screws with the screw driver and set them aside.

Step 4

Locate the battery on the right side of the vehicle near the front headlight. Twist the "Negative" battery cable off of the "Negative" battery post. Pull the distributor cap off of the distributor. Pull the black hoses away from the distributor cap.

Step 5

Clean the distributor cap with a small wire brush. Remove leftover dirt and oil from the distributor cap with a dry towel. Replace the cap back on the distributor using the reverse process. Replace the hoses back on the distributor cap.

Check the Spark Plugs

Step 1

Locate the silver engine block under the hood in the center of the vehicle. Locate the four black hoses coming from the engine block. The hoses are connected to the four spark plugs on top of the engine.

Step 2

Grip a spark plug cover and twist it to the left. Continue twisting until it twists off. Set the cover to the side. Repeat the process for the remaining three spark plug covers.

Step 3

Grip the spark plug with a spark plug socket that fits around the spark plug. Twist the spark plug socket counter-clockwise to remove the spark plug from the rubber plug socket holding it.

Step 4

Inspect the spark plug for oil leaked inside of it. If there is oil inside the spark plug, replace the spark plug with a new one. Check the owner's manual for the specific spark plug your Nissan Altima requires. Repeat the process for the additional three spark plugs.