Rattle noise when I accelerate. Sounds like plastic hitting a fan?

I have a 2003 Ford Focus. Just recently every time I accelerate I hear this rattle noise. The best way to describe it is when you take a piece of plastic and put it to a fan. Or take a baseball card to a bike tire. My check engine light came on and when I had that checked they said it's either the gas cap or I have a very small leak. Could these be connected? Car also makes that sound when I first turn it on.

I have a 2003 Ford Focus. Just recently every time I accelerate I hear this rattle noise. The best way to describe it is when you take a piece of plastic and put it to a fan. Or take a baseball card to a bike tire. My check engine light came on and when I had that checked they said it's either the gas cap or I have a very small leak. Could these be connected? Car also makes that sound when I first turn it on. The rattle may be the exhaust heat shield. You need to have someone who is qualified look at the engine for a correct diagnosis, and not some character at an auto parts store or wherever and whoever misdiagnosed the check engine light! Sorry, but it's impossible to know what the noise is w/o seeing the vehicle

You need to have someone who is qualified look at the engine for a correct diagnosis, and not some character at an auto parts store or wherever and whoever misdiagnosed the check engine light! Sorry, but it's impossible to know what the noise is w/o seeing the vehicle