So my check engine light comes on after ive been idling for a prolonged period of time, lets say 30min. Now it doesnt always happen and it goes away on its own after a day or so, and it doesnt impact the car in anyway. But it still mistifies me as to why it does this. Any thoughts?

 

Did you get the code pulled.. if the light came on it should have stored a code.

 

As above, I'd first pull the code to see the malfunction, but an extended idle can have an adverse affect on components, IACV, O2 sensor, even an electrical drain if any audio upgrades.

 

I always wondered about this as well because I always said to myself I'll take it in the next day to read the code but it disappears by itself.

 

If you have an intake such as aem or k&n I would clean the throttle body, if that doesn't fix it I would unplug the harness to the egr while vehicle is off, and reconnect it after turning vehicle on and back off again. Could be spark plugs too though.... just my .02

 

If you have a lazy O2 sensor it can throw a code if it cools off too much. There's a very good chance its either a misfire or lazy O2. Pulling the codes will tell you for sure.

 

Well i never seen any codes pop up, the only time i see a code is when i dont tighten my fuel cap, its particularly sensitive to that. Other then that it does away on its own, but i will try cleaning my throttle body as i do have the AEM V2 intake. What am i looking to do? just wipe away any grime around the butterfly?

 

You won't see codes .. you have to get them read with a code reader.

 

Fully agreed. Codes are stored whether the light is on or not.

Cleaning the throttle body will have absolutely zero effect. This is not your problem. You will be wasting your time. Get the codes read.

 

Why is your car idling for 30 mins??? Isn't this practice bad for the car as well as the environment?