View Full Version : what causes a car to blow out clouds of black smoke?

07-21-2006, 10:09 PM
What would cause my car to blow out clouds of black ?The scan tool reads bad o2 sensors but i didnt think 02 sensors would make it blow out that much black smoke and the car runs so rich it burns your eyes.Could it be something else like the maf?

07-21-2006, 10:13 PM
the o2 sensor could be making it run rich. thats where the cloud would come from

07-21-2006, 10:22 PM
the 02 sensor would make it blow out very large clouds of smoke?

07-21-2006, 10:39 PM
the O2 sensor would make it run rich. dumping all that excess fuel into the cylinders would make it blow black smoke. the smoke is just unburned fuel

07-22-2006, 03:33 AM
I dont think unburned fuel would be black. IT would prob be more whitish then a black. An 02 sensor doesnt have anything to do with the amount of fuel thats dumped inside of your engine. Thats all the engine. All the O2 sensors do is read the fuel that comes out to make sure its not running too rich or too lean. If it is it will throw a code informing you that its running rich or lean and to get it checked out. The code is informing you that its running rich, so Id get it checked out.

07-22-2006, 12:57 PM
If you have a scan tool like it sounded like you did go into the Data Stream and check on your coolant sensor and see what your O2's are doing and what your fuel trims are. More than likely your long term fuel trim is going to be way into the plus like +25 or something and make sure your temp sensor is at a normal temp. not -40 like most of them say when they are unplugged or something.

07-22-2006, 02:41 PM
Bad o2's can cause it to smoke. They could be dumping in more fuel. The scanner is even saying bad o2's, so try not to look father into it than what it is. Change the o2's, maybe it's time anyway. They dont last forever. There could be a different sensor as well causing it to run rich and dump fuel causing the o2's to foul as well. An example would be having an injector stuck open, causing it to dump fuel, fouling o2's. Your maf sensor could cause it as well. Like the wires being dirty or the famous K&N oil all over it.

Joey7489, the o2's have alot to do with how much fuel is used. The engine can't determine how much fuel it needs without sensors, and there is quite a few. If the sensors are fouled it can make it run rich. If the o2's are seeing the car go lean, they will dump fuel to compensate and vice versa. Sometimes it doesnt throw a code right away. Almost every tuner uses a wide band o2 to tune. Thats because our narrow band o2's suck. The wide bands are way more accurate when it comes to tuning for fuel issues. Especially at wot.

Blank, you could go with the Bosche 13111's. If you have headers or plan to get headers, they would be a good investment. They have longer wires, so no extensions needed for headers. They also have a higher heater wattage, which helps because on almost all headers the o2's are father down stream. So they get the extra heat they need. You can use them with the stock mainfolds.

You probably would get a more accurate answer if you posted this in the pcm diagnostics and tuning section.