Chevy Malibu Engine Knock 2007 Ecotec 2.2

I have a 2007 Malbu LS with the 2.2 Ecotec engine. About 60 - 90 seconds after I cold start the car, it develops a knocking noise in the engine. It goes away after about 5 - 10 minutes when the car is warmed up. Dealer tells me that this is a normal engine noise for the car. Trying to blame it on piston slap.
When I accelerate, the noise gets louder, sharper and higher pitched. It seems to lag a fraction of a second behind the engine getting faster, but that could be my imagination.

Is this normal with the Ecotec 2.2 engine? I have driven a lot of Chevy 4 cylinders including Prism (toyota), Cavalier, Cobalt, Malibu's and Corvette (just kidding on the Vette, but I wish), and none have made a "piston slap".

Please reply if your 2005 - 2007 Ecotec does or does not make any knocking noise on cold start up.[/b]

knocking sound on any car engine is a sign of wear.in the exception of some lifter noise caused by gum build up. I thnk they are trying to brush you off. get another opinion from another dealer and an aftermarket both preferably from a good referal.