What do you mean by "pushing out a lot of fuel"?
If you mean dripping from the exhaust pipe, that's probably water vapor. Nothing to worry about. If you mean the exhaust manifold is glowing orange, the ignition timing is retarded and the fuel is finishing burning after it leaves the cylinders. If you mean fuel mileage is bad, and you smell raw fuel at the tail pipe, suspect an exhaust leak before the first oxygen sensor. Between the pulses of exhaust flow, the momentum creates pulses of a slight vacuum. Outside air can enter the exhaust system through the leak and be detected by the oxygen sensor. The engine computer will see the extra unburned oxygen and add fuel by holding the injectors open longer in an attempt to achieve the proper mixture. Even though more fuel is entering the engine, the oxygen sensor continues to see that fresh air coming in through the leak. Oxygen sensors do not react to unburned fuel, just unburned oxygen. No matter how much extra fuel enters the engine, the O2 sensor will always report a lean condition.
A similar problem can occur from a vacuum leak by the intake manifold. The extra air might enter only one cylinder and again, be detected by the O2 sensor, but the computer can only add fuel to all injectors equally. Most cylinders will have too much fuel while the computer still sees the unburned oxygen. A misfiring spark plug can do this too. The unburned oxygen is detected by the O2 sensor; the unburned fuel is irrelevent. The computer increases fuel to all cylinders but there will still be that darned unburned air.
If none of these things seems to be the problem, you can use a hand-held computer, (scanner) to read the short and long term fuel trims. High positive numbers means the computer is trying to add fuel above the factory preprogrammed starting values. High negative numbers means the computer sees there is too much fuel entering the engine and is trying to do something about it.
So, ... The question remains. What do you mean by "pushing out a lot of fuel"?
Wednesday, March 3rd, 2010 AT 12:27 AM