check engine light

my check engine light is on. driving the car runs ok not top performance. while sitting at a red light or sitting idle the cars idle is not persistant it fluxuates and almost sounds as if sometimes the idle gets so low that it is going to stall out but dosent. every once in a while sitting still i will get this rotten smell almost like a cat smell but i have a new high flow cat. and it smells like it is comming from the engine maybe, i can smell it through the vents at times. ive cleaned all the sensors and checked their connections and i cant find anything wrong anyone have any suggestions i have to do this on my own.

Go to a parts store and have the codes pulled. Most parts stores do this free. That'll be a good start.

ive went to autozone and the code was p1143 air fuel metering control malfunction

One inexpensive thing to try is change out the air filter and make sure the small metal air screen below it is not clogged with dirt. The air screen is held in place by two screws and prevents small animals from making a home in the air box. The air screen in mine was clogged up like a dryer lint trap after only a few years of driving.