90 accord EX Automatic.160,000 miles.Changing my o2 sensor last weekend because I had a code 43. When I unpluged theold sensor I noticed red fluid in the plug. I assume its transmission fluid but I can't see where its coming from. Has anybody had this problem with fluid in the o2 plug. Thanks.

 

It's usually from oil leaking from the distributor o-ring or the valve cover gasket. Maje sure to get the leak fixed before installing the o2 or it can quickly be contaminated.