Prius Spark Plugs


How to replace spark plugs on Generation 2 – 2004 2005 2006 2007 2008 2009 Toyota Prius:

Spark plugs on a Gen 2 Toyota Prius should be changed every 60k to 80k intervals. Some say it should be fine up to 100k to 120k, but it is always a good idea to be cautious. It should be simple and inexpensive, if you have the tools. I recommend the NGK Laster Iridium Spark Plugs – eBay, I have always know they are better quality compared to non-laser.

Estimated job time is 1 hour to 2 hours.

Tools/items required (Affiliated eBay links):

Step 1: Remove the 2 bolts on relay box with the 10mm socket.


Step 2: Disconnect the harness on the ignition coils. This can become difficult but I figured the best way to do it is by prying it from the inside of the harness while at the same time pressing on the lever and pulling it out (example image below).


Step 3: Clean the surface around the ignition coils to make sure no debris falls into the spark plug. You can use compressed air to blow away any debris. Cleaning Air Duster – eBay

(Repeat steps 4 to 6  for each spark plug)

Step 4: Remove the 10mm bolt on the ignition coil, pull the ignition coil straight up, and check for signs of wear to judge how the engine is performing.


Step 5: Individually remove spark plug with a 5/8″ spark plug socket or deep socket on a 4″ extension ratchet. It should be around 30 – 35 full spins counterclockwise to loosen. If you don’t have a spark plug socket that holds the plug you can use the long nose pliers to reach and remove the spark plug from the the engine. If spark plugs are hard to loosen you can use a little PB blaster or WD 40.

Spark Plug Socket 3/8-Inch Drive by 5/8-Inch – eBay

Step 6: Inspect the spark plug to judge the level of wear and make sure it is normal. Make sure the new spark plug gap is set at the .043 specification. Replace with new spark plugs and if possible new ignition coils too. Torque the spark plugs at 13lbs.

Digital Torque Adapter 3/8″ Drive – eBay

Step 7: Bolt ignition coils, relay box, clean up, and enjoy your Prius.



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