Hello, my check engine light came on today and I didn't notice anything weird until after driving home. When I put my car in park and let it idle, it began to go below 1000rpm to 800 rpm then back up above 1000rpm. The engine seemed to be moving when it went really low as if it was trying to keep itself steady. Just wondering if you had any ideas as to what the source might be from. I know there is an air leak but not sure where. I have a feeling it has to so with my turbo cause it seems like more air is going in when I drive as if its pushing the car back when I move forward. Hope this makes sense. Just needing a few ideas if possible. Thank you

First find and fix the vacuum leak. Second, get the codes read at the parts store and fix whatever is turning the CEL on. It might be coming on from the vacuum leak.

Most common problems with the engine light are not serious at first. The light is just asking you to do a regular engine check. Your owners manual will define these check. If you don't have one than just remember that they all basically include the following: AIR FILTER (engine can't breath), OIL CHANGE (dirty oil will leave film deposits on censors causing a false positive), DIRTY FUEL (a fuel system cleaner should be used at every oil change to keep your fuel injectors and filter clean). All 3 of these will cause the problem you stated. The "air leak" needs to be fixed however, if it was there before this problem, then chances are it is not the cause.