I am going to be replacing the oil cooler o-ring on my wife's 99 Prelude BM, this was the cause of an oil leak that has been gradually getting worse.
My question is can coolant leak into the engine through the oil cooler? Because after me being deployed for 3 months the car has had a rash of problems kick up. Here's some info:

- Engine coolant wont stay filled. No visible leaks.

- CEL threw codes 71,72,73 (Misfires in cylinders 1,2,3)

- Removed Valve Cover to find coolant mixed with oil all over the valve cover (just on the valve cover, not lots, but no coolant is good) I couldnt see coolant anywhere else. Diptick does not have any signs of coolant.

- Spark Plugs are clean

My guess is i have to replace the head gasket... but the only thing that i dont understand is when i start the car, it has a rough idle, then is steadys itself and it runs perfect... That's why i dont think it's the head gasket. If there is a chance that coolant can get into the engine through the Oil Cooler that may be a possible cause. Any input? Maybe i'm missing something.

I posted this in the civic section as well because the engines are similar and im a civic owner and i've always had good help here.

I just want to beat this car already. It has been a monster of problems since we bought it. Thanks in advance for any information fellas.