there seems to be a lot of talk about engine noises these days. You may recall I had one and brought the car in to the dealership to check it out before my warranty ran out.

My noise was intermittant and sounded muffled. Perhaps fuel injectors I was told.

Dealer said it was the air pump and he tightened the belt up a bit. I still hear it. But I do believe it's the air pump because the noise seems to be cycling.

Questions:

Is it normal to hear the air pump? Or could it be leaking?

What is the pump doing? Is it like the old air pumps in the 70s that put air in the exhaust manifold to held reduce emissions at the tailpipe? (alwasy sounded like a patch fix way of reducing emissions, to me)

General advice requested. :-)