Q: Car is is idling low, poorly, and is getting bad mpg.

asked by on

A couple months ago my car threw a check engine light for both upflow o2 sensors. I went to a mechanic that I've known for 20 years that hasn't ever steered me wrong and he replaced both of them. How ever every once and a while the check engine light comes back on and it reads those 2 upflow o2 sensors. After a short while the light will go back off though. The constant symptoms no matter if the code is there or not are: *The car idles at around 500rpm *At stop car will shake and rpms will drop to almost stall and bounce around before going back to 500rpm *Very poor gas mileage *I believe slower acceleration by a little I'm also pretty sure i have an exhaust leak by the sound of it.

My car has 126000 miles.
My car has an automatic transmission.

Based upon the symptoms you are describing, it sounds like you may have a faulty camshaft position sensor. The camshaft position sensor is a magnetic sensor that monitors camshaft speed to regulate ignition timing and fuel injection timing. It gathers and sends information about the car’s camshaft speed to the car’s electronic control module. This information is used by the computer to further calculate the time of ignition and the timing of fuel injection required by the engine. When this is not working properly, you may experience a drop in power, poor idling, poor fuel mileage and problems starting the vehicle. As the sensor begins to fail and gets worse over time as the signal it provides to the computer weakens. I would recommend having a professional from YourMechanic come to your location to diagnose your camshaft position sensor.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Car is is idling low, poorly, and is getting bad mpg.

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Heater stops working during idling

Hello. I recommend checking the operation of the thermostat to ensure it opens and closes at the proper temperature. You also could have some air in your cooling system causing the heating system to blow cold at inappropriate times. To...

Q: What does it mean if the message center shows the warning “engine oil change soon?”

It’s absolutely essential that you keep up with normal maintenance, like oil changes, tire rotations, air filter changes and the rest. Your car is designed with a reminder system designed to help make keeping your car serviced easier. If you...

Q: My brake fluid is leaking rapidly (in about 3 minutes) out of the rear right tire.

Hi, thanks for writing in. A brake fluid leak is a major problem and the vehicle should not be driven until the leak is diagnosed and repaired. You may have a damaged hose, rusted through brake line, or a leaking...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.