What are the possible reasons that my fourth piston is not sparking. I am pretty sure the spark plug is broken but I am not sure. The car is a 2006 Scion XB.

Thank you.

  • Broken/dirty spark plug is certainly the obvious cause - but not the only one. Can you give us some info on the make/model/age of the car? – motosubatsu Oct 30 '19 at 13:03

I am pretty sure the spark plug is broken but I am not sure

That's almost certainly the issue. Replace the spark plug and try again, if the problem is fixed, you're all set. If not, then there are more things to check:

  1. The ignition coil, on this vehicle I believe it's located above the spark plug. Try swapping two of them and see if the problem follows.
  2. The wiring. Make sure the coil is connected properly and that the coil is correctly and fully connected to the spark plug.
  3. Fuel injector. Harder to check without special tools, you may need to take it to a shop at this point.
  • +1 bang-on what I was going to write :) and you're correct the Ignition coil is located above the spark plug on these (it's a 1NZ-FE engine). Some useful info on testing the spark plugs and coils here – motosubatsu Oct 30 '19 at 13:40

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