Besides the noise, there actually is a way a leak can cause problems. Between the pulses of exhaust gas flow, the momentum creates little pulses of vacuum that can draw in outside air through that leak. The oxygen in that air will be detected by the oxygen sensor as a too lean condition. In response, the Engine Computer will request more fuel to go with that air. No matter how much extra fuel it requests, there will still be that unburned oxygen so the computer will keep asking for more and more fuel. The mixture going into the engine will be way too rich, you might smell raw fuel at the tail pipe, but the computer will think the mixture is too lean and it has lost control.
Most of the time that doesn't happen and the engine runs fine. This is one of those scenarios that are the one out of a hundred cars that no mechanic can figure out.
Sunday, June 17th, 2012 AT 4:29 AM