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Q: Car revs at stop sign, no check engine light

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So I have to get my exhaust completely replaced, that I already know, but now I'm driving and my car accelerates slowly but it revs, and then if I'm at a stop sogn or a light and go to hit the gas a little the RPM goes up to about 2/3. Or if I'm sitting there it will idle sometimes. I called my mechanic and he didn't seem to eager to have me come in.

My car has 130000miles.

This may be a result of a faulty oxygen sensor reading as a result of your exhaust system (presumably your catalytic converter) not operating effectively. As you may know the oxygen sensors which are part of your emissions system read exhaust gases to determine whether or not the appropriate amount of oxygen is present in the exhaust. Based upon this reading, this information is relayed to the car’s ECU which then makes a determination as to whether or not to add more or less fuel to the engine. When too much or too little oxygen is present, this will cause check engine light to come on. Too much oxygen may be present in the exhaust gas due to things like an exhaust leak, a vacuum leak, a faulty mass air flow sensor (causing a lean fuel condition) or faulty fuel injectors. Too little oxygen may be present in the exhaust gas may be caused by things like a clogged air filter, a failing mass air flow sensor (causing too much fuel to be introduced to the motor), bad fuel injectors or a clogged catalytic converter. When the O2 sensor is not working properly, this will cause false readings to be relayed to the computer causing inaccurate adjustments to be made to the intake and fuel system in your engine. You may also notice a very strong smell of fuel. I would suggest having an expert from Your Mechanic come to your home to diagnose your emissions system.

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