1998 Dodge Ram rough idle

When my engine is in park and idling, initially it's fine. According to the tachometer on the dash it's idling at about 7500 or so. After about 3 minutes though the idle starts stumbling and hissing from the top of the motor right under the air filter. The exhaust stinks. Very rich I think and the tail pipe is spitting fluid, though it does not smell much like gas. The rpms go down to about 4500 and just shy of a stall. What does this sound like to yall.