Mazda 3 2004 Engine Revving when car not moving

Question

I recently noticed when my car comes to a stop engine running and ac on the engine revs as if it wants to move forward. The rev isn't huge. When i am in traffic and holding down on the brakes, if i release the brake without pressing the gas pedal and allowing the car to roll forward on its own the car begins to rev.

I took off the ac but this didn't solve the issue. What i did was turn the engine off and turn it back on and it stopped. The problem is not noticeable as i start the car only when i drive for 30 minutes or so.

I am not sure what can be causing this since the only thing i did with the vehicle was full gas. I am assuming the issue can be with the fuel. I am also thinking the idle sensor could be going bad or could it be a dirty throttle body.

Any help and advice would be appreciated guys.

Answer 1

Most likely case is a bad throttle position sensor or a bad air sensor (some cars use mass air flow, some use manifold pressure). This is typically not something that can be seen in codes, but must be identified by comparing sensor data and graphs.

Other possibilities could be a vacuum leak, but that would probably throw a code/check engine light. Of course, there are also other outlier possible causes like a computer issue, valve leaks, or piston ring sealing. But usually you would see many other problems for any of those cases