TEST 9: Other Causes Of A Misfire
So you've done all of the spark tests, and still your Nissan Altima is running rough (rough idle) and/or the Misfiring. Well, here are a couple of suggestions that might help:
- The valve cover gasket is leaking oil onto the spark plug wells (tubes) and soaking the spark plugs and spark plug wire boots in oil.
- Over time, this oil will cause a misfire as the oil cooks and turns into carbon tracks.
- The photos in the image viewer show you what a carbon track looks like on the inside of the spark plug wire boot and on the ceramic insulator of the spark plug.
- Engine compression test
- One of the most overlooked diagnostic tests to find the root cause of misfire is the compression test.
- You'll need an engine compression tester of course.
- The engine compression readings between cylinders should not vary more 15%.
- Carbon tracks on the spark plug(s) and in the inside of the spark plug wires.
- The photos in the image viewer point (the orange arrows) to what carbon tracks look like.
- Replace the components as affected with carbon tracks.
- Broken spark plugs.
- This usually happens at tune-up time, if you have dropped one on the floor.
- You power washed the engine, this is something that should never be done on any Nissan vehicle.
If this info really saved the day, buy me a beer!