Unburned Fuel coming out of the exhaust

[Dinosaurdriftteam]

I recently did an emissions test and it wouldn't pass because most of my exhaust is unburned fuel. I also have a check engine light on for an O2 sensor. What should I do?

[bentotdagr3at]

check your plugs and see if they are wet. might have a leaky injector(s).

[Dinosaurdriftteam]

So I did check them and They are BLACK as can be and the had a bit of oil on them and a bit of gas. Then I checked the compression to solve the oil of the plugs but the compression was fine and about 140-150 psi on a cold engine. So it is possible that I might need new injectors but its just a theory.

[amiry36]

Well, if the check engine light for the o2 sensors are on, then thats a big give away that there is something wrong with them. I had the same code but i got away with pulling the o2 sensors out and cleaning them with brake parts cleaner and then putting them back in. Also as suggested, check the connectors that go to the o2 sensors first. If they are coroded, they prevent the sensor to send data to the ecu. The connectors are located on the each side of the engine. Just look at the sensors and you can trace the wiring to the connector. You can also clean the connectors with parts cleaner and a toothbrush. Before all this, i would test the o2 sensors them selves while on the car. Just google 300zx o2 sensor testing and you will find write ups. Its rather easy to do and a good place to start. Honestly, I'm not sure why a leaky injector could be the problem. However, you can ohm test the injectors themselves to see if they are good or not. Simply disconnect the connectors to the injectors. Bring your ohm meter and connect the red and black prons of your ohm meter to the injector male prons! Not the wiring harness. The reading should be between 10 to 14 ohms. If higher than 14 ohms, the injector doesnt supply enough amount of fuel, therefore resulting in a lean condition. If the reading is below 10 ohms, then the injector is supplying too much fuel, therefore causing a rich condition (which could result in unburnt fuel).
Also one last thing, check the timing of the engine with timing light. If it is less than 15 degrees (closer to 0 degrees), before top dead center, then the timing is off which causes the fuel to not burn completely, hence giving you high unburnt fuel readings.
Keep us posted of what happens
Take care.