Oldsmobile/Buick Repair: Rough idle at start, spark plug wires, buick lesabre

Question
I own a 1987 Buick LeSabre Estate Wagon.  It is a 307 V-8.  It is in excellent condition (well it was).  Last summer my 2 little nephews were helping me wash it.  When we finished I opened the hood to check the oil.  I went inside to get a rag and then came outside to find my nephew spraying the engine with water!!  It started but being already started that day it idled just a little rough.  The next morning and every morning after that it cranks fine to start but immediatly runs so rough that the engine shakes side to side. and puts out black exhaust.  the idle gets smoother and smoother which each rise in engine temperature until it runs normal at full temperature.  the exhaust also returns to normal at full temperature.  I replaced the spark plug wires, distributor cap and the rotor and that did nothing.  I am going to replace the spark plugs and hope that works.  Did my nephew ruin my Buick?  What else can i do to get it back to the way it should start.  It has always started the way it did in 1987; I want that back!!!

Answer
hello graig
i would check for water in the coil this could be giveing you problems and it is moitore in the gas i would start runing some dry gas in the tank over time it should straghten out it will take some time water is the worst hope you changed the oil and also when u say black smoke this is carbon get some carb cleaner and spray it is the carb while the car is runing . good luck to u please rate my serivice pete