leaking coolant

Hi, I have a 2002 silverado with a 5.3. I am having problems with coolant leaking... only its not. I am unable to find it dripping anywhere and it goes down very slow over a period of time. The truck idles really rough and seems to die sometimes. This happens regardless of whether it is cold or warm. I originally thought it was the infamous intake gasket problem but the codes i get are #4 misfire and lean condition on both sides. I have also noticed the oil pressure to be lower than usual, around 30 at idle. What is normal for oil pressure at idle? Also what could be causing my coolant leak? I am planning on going to a mechanic as I have had enough of this truck. I would like to have some education before I go into the shop blind. Thanks, Derek

I just replaced the water pump gaskets on my wifes 03 1500 z71, and my 03 2500hd. they both had a very small leak at the water pump gasket that you could barely see, but the level slowly fell. the way they were leaking the coolant would trickle down the block and evaperate due to engine heat. never had any puddles, I had to use a shop light and take the skid plates and splash shields off to see it. gaskets were only about $20 bucks and I also flushed the coolant as I was draining it anyways. My 2500hd has 113000 miles and hers has 70000 and the dexcool still looked good(clean not gelled or nasty).

had the same issue with my gmc, same engine, same senerio only it was a small leak at the thermostat goose neck gasket to intake. This drove me nuts for some time as it would leek and evap. It just happened to get bad enough to find one day.
the missfire could be an indication of the intake gasket, or other things. wet dist. cap/cracked or coroded. plug wires ect.
Look into the coolant issue first and make sure that is not the problem causing the misfire

had the same issue with my gmc, same engine, same senerio only it was a small leak at the thermostat goose neck gasket to intake. This drove me nuts for some time as it would leek and evap. It just happened to get bad enough to find one day.
the missfire could be an indication of the intake gasket, or other things. wet dist. cap/cracked or coroded. plug wires ect.
Look into the coolant issue first and make sure that is not the problem causing the misfire

this is a 5.3l 2002 vortec engine there is no distributor cap. you will , remove plugs look for a very white looking plug if you find one this is probably a head gasket and with the code #4 cyl. is the area and passenger side of engine. i hope not but it looks that way from here...the oil will have white sludge forming and oil fill cap will have condensation. also if it is a head gasket with coolant cap off you will see coolant bubble if real bad leak at head.

on my 2000 5.3l oil pressure 40-60psi. 40 idle in drive , 60 2000rpm

leaking waterpump gaskets are very comon for these vehicles. intake is dry so it won't leak coolant. intake gaskets are probably setting the lean codes
missfire

also check the plastic side tanks on the radiator for cracks especially around the oil cooler fittings these are prone to crack and you can replace the tank instead of whole radiator . tanks cost $160.00 verses $400.00 for a radiator. what type of oil are you useing?