I'm guessing it's coming from the part that's between the engine block and the oil filter. I took off the oil filter, there's a 30mm size nut but I don't know if the nut is removable.
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1993 Honda Accord Question: Oil leak between oil filter and engine block
Answer #1Bret Bodas from RepairPal Test Shop, November 19, 2009, 12:11Master
The part is the oil cooler. The nut is removable. You'll need to replace the O-ring between the cooler and the block, the sealing ring on the bolt (if equipped) and I would replace the coolant hoses to the cooler too.
Here is a pic: http://img45.imageshack.us/img45/8453/13ss00a05xf7.gif
#18 Oil Cooler, #19 bolt, #33 o-ring