2009 Chevy Cobalt

06/09 Cobalt began stalling when accelerator was pressed only to the extent needed to maintain desired speed. But when accelerator was applied heavily the car accelerated properly. No engine lights. Took to dealer Service.

Dealer diagnosed problem as a defective fuel injector and replacement part was ordered.

06/16 Picked up Cobalt from Dealer Service. 2 Miles down road same problem as described above re-occurred. Had an engine light this time. Returned Cobalt to Dealer Service.

06/16 Called Dealer Service and they said they had a new part on order. (Did not specify what part).

06/17 Dealer Service called and said that mechanic took a sample from my fuel tank and determined that I had water in fuel. Said that repair would cost $320 since it wasn't covered under warranty. (Note that last fuel stop had been over a week before problem occurred).

06/18 I called Dealer and they said the fuel tank had been drained, but that an engine light indicated that my catalytic converter needed to be replaced. Part is on order at present.

With the latest "catalytic converter" hitch, this service problem with my Cobalt is no longer passing the "smell test" where the claim of contaminated fuel is concerned.

I'd appreciate an outside opinion about the validity of my Dealers claim that there was water in my fuel. Or any idea of what might be really happening with my Cobalt?