Engine rattle

I checked with my mechanic and he said he did check the heat shields and the catalytic converter was okay. He said the noise was coming from the front of the engine, so he didn't think it had anything to do with the pistons.

Thanks for trying to help. Your suggestion was beyond my skill set and strength. However, the problem turned out to be a cracked flywheel which was replaced by a local transmission shop for $750.

What could a rattling/grinding noise be under the hood when I start thr car it will go away for a minute then comes back?

What you may be hearing is the timing chain rattling against the block. On high-mileage Stratus's upon initial start-up they will rattle for a few moments and then the noise goes away. If you have the 2.7 make sure you change the oil promptly or you will have major engine damage due to sludge build-up. Google this engine, you won't like what you hear.

I have a 1999 dodge stratus 127,000 miles, 2.4 dual overcam engine. My check engine light came on about a month ago.I had the dealership scan it. They said I needed to replace both my oxygen sensors.I drove it for three weeks without replacing them. Then I started hearing a loud rattling noise, only on acceleration, coming from in front of the car.I replaced both oxygen sensors but the rattling noise is still there. Please help me. This noise is driving me crazy.

When I am in park theres no noise. Its when I am driving, its the loudest between 30-40mphs. When I let off the gas there is no noise. Other than the rattling the car runs great.

The code was PO172 system too rich (bank 1).

Yes, my check engine light came back on after I had the oxygen sensors replaced. I went to auto zone they said there were no new codes. They cleared it. The light hasn't come back on yet. I have not driven it much sense I had that done. When the rattling noise starts the car seems sluggish and there is some vibration. Oher than that the car runs fine. It seems like the noise is coming from under my feet.