[ladagosta]

97 chevy lumina auto, v6, 3.1 engine
first off the car has routine oil changes has 81,000 miles
last change was done October 08 a month later it developes this missfire, loss of power, and a loud tapping noise from the engine compartment.
thought it might be the lifters or valves we took the valve cover off when it was hot and turned the engine and everything appears fine: lifter, springs and valves appear to be working fine. WHen the # 3 is down it makes a loud chatter, there is some sludge in there, oil appears to be watery, clear not dark or anything.
not milky in texture, no oil residue in the water..so it does not appears there is a crack in the block or blown gasket.
Can any one tell me what could be causing this tapping noise.
is this the piston slap everyone talks about?
next chance I get I will try to clip a video of the noise and post
Cams?
rockers?
valves?
maybe injectors are clogged?
if everything else seems to be working fine.
Does anyone know if the sparks plugs can make a difference on this make model?
I have considered changeing spark plugs thinking maybe one cracked.. not likely
which would you use to try and resolve this issue? : STP, EOS (Engine Oil Supplement)
or sea foam?
a mechanic over a year ago told me there was a light on and he would take care of it and disconnected it.. turns out I was told that it was the "check coolant soon" light, the temp gauge has not run high.. but could I still be leaking water into the engine even if the oil isnt pudding like? or the radiator does not have oil in it?

The car is not driven but 5 miles a week and I dont want to loose the engine over this.. so anyone have a past issue or know of known cases where this is resolvable please post back.
money is an issue on a set income and no money to buy a new car and
well little to put to repair if it is a cam issue
ty