One problem related to manifold/header/muffler/tail pipe has been reported for the 2007 Saturn ION. The most recently reported issues are listed below.
Vehicle traveled through water puddle on a rain soaked roadway. Puddle was no deeper than mid- tire height level. Engine stalled out causing loss of steering and some braking ability. Engine was restarted and vehicle drove less than two miles home. Next day, engine started after numerous attempts. Engine skipping and a check engine light was on. Vehicle was driven to dealership. Dealership reported that water had been drawn into the engine air intake, which is located at front bumper level on right side of vehicle, and into traveled through the system into the engine. Water present in at least two cylinders, intake manifold, and oil pan. Engine had to be replaced. Dealer, nor manufacturer, would honor warranty. Auto insurance claim filed and paid. I am concerned that it is unsafe to operate this model in rainey weather.