Rich vs Lean? Can someone please explain this (causes, etc)?!?
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Joined: Apr 2000
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From: Melrose, MA
Think I'm running rich...always get some black crap on the lower part of my exhaust tips after
cleaning them. I think I should be getting slightly better mileage too...so that adds to my theory. I need to get someone with a VAG to confirm this.
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From: San Diego, CA
re: rich vs. lean
A car generally runs ideally with a certain air to fuel ratio. Call it's A/F ratio, or number. A rich condition exists when th ratio is smaller than the prescribed A/F number (or the F is bigger than it's supposed to be), and a lean condition exists when the A/F number is high than prescribed (or the A is bigger than it's supposed to be). On a carb car, lots of things can cause a car to run rich, or lean, however on a fuel injected, or computer controlled injection, like the A4, it's a little more difficult. Usually faulty parts cause the situation, like a faulty O2 sensor, a torn boot, or hose, a faulty air flow meter, etc.
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Causes: (1) O2 or other sensors not functioning properly; (2) ECU poorly programmed/malfunct. . . .
(3) mechanical malfunction/blockage in fuel/air systems.
Just think through how too much/little fuel/air could get into the cylinder; you get fuel from the fuel pump-rail-injectors and air through the airbox-MAF-plenum-TB-Manifold. The ECU should correctly control the mixture if everything works right.
Despite our advances in electronics and technology, we remain like our prehistoric ancestors playing with fire. The internal combustion engine remains a fairly primitive invention, because fire will always require fuel and oxygen in the proper amounts to burn.
Just think through how too much/little fuel/air could get into the cylinder; you get fuel from the fuel pump-rail-injectors and air through the airbox-MAF-plenum-TB-Manifold. The ECU should correctly control the mixture if everything works right.
Despite our advances in electronics and technology, we remain like our prehistoric ancestors playing with fire. The internal combustion engine remains a fairly primitive invention, because fire will always require fuel and oxygen in the proper amounts to burn.
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want to learn..would anyone have an 02 graph of a car running rich vs. one that is running lean? TIA
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