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?

 

When the wrench light comes on, a generic scan tool may not read the codes. You need a little higher quality tool to read the codes. I hate to venture a guess without some code to research first. Sounds like something in the throttle body, TPS area though. Or maybe low fuel pressures.