When I push the accelerator, the engine idles down low

I went mudding and hopefully it wasn't the last time in this truck. But I started having problems very shortly after. I also had a really loud system which drained the battery pretty well, that's fixable but I don't know what I did honestly. Anyways, when I push the gas the engine idles down low and then returns to normal while making an abnormal noise. It was loud before, really loud, but this isn't normal and I may just have to wait until I can get it to a shop. We may try to replace the oil filter soon and get a new battery.