I have bought a used 2006 Freestar. I noticed that after 10 miles of driving my Powertrain wrench flashes non-stop. But no codes pop up when scanned. Recently on a long trip I was climbing a very shallow hill when my RPM's started fluctuating and it seemed to have no power to climb the hill. And i hear a burping noise from the engine compartment. Any clue as to what might be going on in there?

 

I suggest you take it back to the dealer and have them check your Catalytic converters out. My and my friends went at the same time at 80,000km or 50,000miles. Ford emmissions warranty covers this for 8years in Ontario, Canada. I'll bet yours is plugged just the same.