I suspect it has to do with the intake air temperature sensor. The intent of the fresh air intake is to warm the air for better fuel vaporization, therefore better fuel mileage and lower emissions. Cold air systems are used in racing applications where excessive under-hood heat expands the air and makes it difficult to pack the cylinders for high power / high speed. Turbochargers overcome the cylinder filling problem but the heat generated must be removed with an inter-cooler. That's a different problem than with just normal driving.
Too many people think a cold air intake is going to provide free extra power by condensing the air so more will go into the engine. That is true, but then you still have to add more fuel to keep the mixture at the correct ratio to prevent stumbling and hesitation. More fuel and that extra air means a higher engine speed, so you have to let off the gas pedal a little and the Engine Computer has to reduce idle speed a little. That means less air and fuel, so what did you gain?
The only thing a cold air intake will get you is more power at very high engine speeds, and the tradeoff is wasted unburned fuel at all speeds. There's no free lunch. The numbers game is so competitive among manufacturers, if there's anything you can do to increase performance or fuel mileage without adversely affecting tail pipe emissions, they would surely have done it already, and advertised it.
The first thing to do is get the description of the fault code. The listings start at P100. Look at the intake air temperature sensor to see if it's sitting in the fresh air stream or is blocked. Check the electrical connections. Sometimes you can get a clue by when the Check Engine light turns on. If it stays on continuously when the ignition switch is turned to "run" but before the engine is started, a sensor or wiring problem should be suspect first. If the light doesn't turn on until the engine is started or has been running a few seconds, a performance problem with a sensor is more likely the cause.
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Saturday, February 25th, 2012 AT 11:44 PM