How to Change the Plugs on an Altima 3.5

by Robert Morello
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Spark plugs provide the electrical spark required to ignite the fuel and air mixture that is compressed inside engine cylinders with every stroke. The plugs deliver current to the cylinder from a distributor via spark plug wires arranged in precise order. If the spark plugs are worn or fouled, the vehicle will not run up to its capabilities. Blackened plugs can indicate an oil leak, wet plugs can indicate that there is no spark and fuel fouling can indicate the incorrect fuel-air mixture on the V-6 Altima 3.5L.

Step 1

Open the car hood and let the engine cool for one hour if it had been running. Touch the engine head lightly to make sure it is cool enough to work on. Determine the proper size socket to use by measuring them against one of your new spark plugs. Use your eye to see which sockets seem to fit and slip the plug into each one until you find a match. Remove the plastic engine cover by unscrewing the two set screws located on the top using your Philips screwdriver. Pull upward on the cover until the anchor posts release and it comes loose.

Step 2

Detach the spark plug wire from the spark plug on the front left end of the engine. Place your socket over the plug and apply pressure in an attempt to turn it counterclockwise. The front plugs should be fairly easy to remove unless they are very old. If they do not loosen easily then spray some WD-40 or other lubricant around the threads of the plug and wait for it to work its way in and loosen things up. Use your ratchet and remove the plug. Dispose of the old plug.

Step 3

Gap a new spark plug using your spark plug gapper. Slide the gapper between the plug filament and the electrode to measure the gap. If the gap is too large turn the plug over and press down on the top filament until it comes in contact with the gapper. If the gap is too small, use a flat head screwdriver to pry it open a bit and then close it over the gapper in the same manner.

Insert the spark plug into the cylinder head and turn it clockwise with your fingers. Turn it as far as you can manually then use your ratchet to tighten it the rest of the way. The fit should be snug but not overly tight. Reattach the spark plug wire and move on to the next plug at the front center of the engine. Continue this process for all six plugs. Reinstall the plastic engine cover.


  • Rear plugs are harder to work on because they do not provide such easy access. You may require socket extensions in some cases to reach the plugs while avoiding impediments.
  • Using a special spark plug socket can makes the job easier. Spark plug sockets have a rubber inner surface which acts as a suction cup and grabs onto plugs as they are installed or removed thus preventing them from falling free and becoming lost or broken.


  • Applying too much force to stuck spark plugs can result in breakage. If a spark plug breaks while in the engine it your options for removing it are limited. Spray a bit of WD-40 or other lubricant to loosen the threads first.

Items you will need

  • Ratchet set
  • WD-40
  • New spark plugs
  • Spark plug gapper
  • Spark plug socket (optional)
  • Philips screwdriver
  • Flat-head screwdriver

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