If the oxygen sensor goes bad and tells the computer that the engine needs more fuel when it in fact does not, the vehicle will run rich. Telltale signs of a rich-running engine are a noticeable odor of gasoline coming from the tailpipe, erratic idle, fouled spark plugs and the aforementioned loss of power. Although the computer actually does all the air and fuel adjustments, it is the oxygen sensor's job to tell it which way to go. Since a rich condition robs a vehicle of power, a bad oxygen sensor can cause poor acceleration. If your vehicle is running rich, replace the oxygen sensor to see if that solves the problem.

While the oxygen sensor can indeed cause an engine to run poorly, slow acceleration could also be a clogged catalytic converter, or CAT. The CAT is located further down the exhaust pipe from the oxygen sensor. Its job is to superheat the exhaust fumes before they reach the tailpipe, so that the result is cleaner emissions. Over time they clog up and cease to work properly, which can result in poor acceleration, an erratic idle and failed emissions tests. In a new, clean-burning engine, the CAT will perform effortlessly and do its job. However, if the oxygen sensor goes bad, which may result in more emissions, the CAT can fail prematurely, so the two problems can actually run hand in hand.