My car has been idling poorly. It has difficulty staying up as well. I have to apply the gas and rev the engine up to get it to run. While idling, it would occasionally increase the RPM all of a sudden and stay at high RPM. This would keep the car running at the constant speed without me applying the gas. Also during idling, it happens that the RPMs decrease to 650 and it seems as if the car would turn off. So, I then put it in neutral to keep it running. I had the spark plugs replaced. Also the fuel pump relay is new. I changed the oil. What could be wrong?
There are many different items that can cause the vehicle to idle poorly. The most common would be the spark plugs and wires, MAF sensor, vacuum leak, IAC valve, exhaust leak, or oxygen sensor failure. I recommend having the vehicle checked by a professional before blindly replacing parts. A qualified technician, such as one from YourMechanic, will be able to diagnose the idling issue and perform any repairs required.