So....my neighbors daughter is the proud owner of a 2006 Chevy Aveo and it started randomly misfiring and idled and ran poorly.
After plugging my scanner into it, codes for misfiring and o2 sensor issue's, I did the obvious and cleaned connection's, airflow sensor and cleaned throttle body, which was caked with oil deposit's...still same codes and more... The o2 sensor's were pretty bad so I changed both as the car would not pass smog due to ck eng. light illumination. Perplexed, I started reading possible issue's on these forum's and found a myriad of possible problems including notorious bad intake/exhaust valve's, worn timing belt, crank sensor etc.
I ended up visually testing the coil, and found the #2 coil was not firing at the plug, and after changing the $79.00 coil pack everything went away, no ck eng. lt, and car runs like a champion! Next time I will diagnose coil pack first as this seem's to be a common breakdown issue!