Q: How can I tell if the fuel injector is bad or if it is just the o-rings that need to be replaced, without taking them out to check?

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Had issues all of a sudden with the car, seemed to happen right after fueling. A few miles later pulling into the driveway the car started sputtering like losing power and then died. The abs and traction control light came on. Tried to restart it and it had a VERY strong fuel smell and white smoke and was hard to start. After smelling the gas we stopped trying that day. Put the scanner on it and ended up replacing a sensor and took care of one problem and the other code said #5 was misfiring. We decided to replace the spark plugs and wires and the mechanic said that there was a lot of carbon and fuel on #5. How can we tell if it is just the orings or if it is the injector itself that needs replaced? Still have fuel smell and white smoke. There is no coolant leaking in, the oil looks fine.

My car has 130000 miles.
My car has an automatic transmission.

A: Hi and thanks for writing in. When it comes...

Hi and thanks for writing in. When it comes to determining what part to get, first you need to know what each part does. The O-ring on a fuel injector serves two purposes. The o-ring seals the injector from leaking any fuel out of the engine when the engine is running. Also, the o-ring creates a seal to keep air flow strong so there are no vacuum leaks on the runners of the engine's intake. When there is a lot of carbon on a cylinder, that carbon is unburnt fuel and can cause a lot of problems. Carbon is sticky and cause the rings to not expand making a cylinder have internal blow by. Plus, carbon holds heat, so when fuel is entered, then the fuel can ignite before the spark plug is energized. This is called pre-detonation. White smoke from the tail pipe is an indication of too much fuel in the exhaust system. I recommend getting an engine cleaner for the fuel system and vacuum system. Some suggestions are fuel injection cleaner or sea foam. Sea foam is very powerful and you would need to check the label before using it. Then after cleaning the engine out, drive the vehicle around to see if the problem continues. I also recommend replacing the injector for it probably is leaking fuel and not spraying it. If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make or suggest any repairs as needed.

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