97 Monte z34 random misfire problem

I just bought a 97 monte z34 with 118k miles for 600 bucks. It has two possibly related or seperate engine problems

the engine in this car is a 1997 3.4 liter dohc

the first is the most baffeling. the ecu is trhrowing one code p0300, random missfire. the engine has a small dificulty starting (one or two more cranks than it usualy takes a engine to pop over) after it starts it has a rought idle. when putting the engine in gear it hesitates and the missfires will get so bad the ecu picks it up and throws the light on(that happens when i clear the code after starting it). If you floor the gas from a complete stop the engine will die every single time. if your gentle with gas and ease it up it accelrates to first (its an automatic) but when it wants to shift you have to let off the gas a little or it will seem to shift very slowly. when going up a hill or accelerating it feels like its runing on half its cylinders.
the engine also uses coolant but seems to leak it from no where
i suspect it has a bad gasket but could a bad head or intake gasket do all this
when engine is hot i can smell something buring which i think is antifreeze and it comes from behind the engine by the fire wall,to see it i would have to take the long intake plenum off


list of things the old owner seems to have replaced
timing belt
plugs and wires
oil is clean but i suspect they changed that to

the other problem is not as complex but may be related and its sounds like a rod knock and i think a history of water in the oil from some sort of gasket leak could have caused it. so tommorow i will pull the oil pan and see what i can see for coolant in the oil and if there are any bad bearing on the crank shaft. the valve train is quiet as can be, the loud knock is quite at idel and gets louder with increase in rpm.

pritty much the engine runs terrible. driving it feels like the ultimate granny car so it being my second car which has a beautiful interior and low rust body i was wondering is it cheaper to swap the engine or forgoe troubleshooting and repairing. car has 118 thousand miles so fairly young rides very nice

any help would be greatly appreciated since cash is a lil tight i dont want to take it somewhere so they can find ways to scam me something like this they could realy have a few gos with.
thanks

:banghead: update: i tore down as far as taking off cam covers plenum and timing belt cover and from what i see the timing belt is decently tight not to loose. i think i found the culprit i got a haynes manual and it says the flats on one pair of cams should be 180* apart from the other piar, so if one side is up the other side is down. but they have got all four cams with the flats facing up!!! i even turned it over many times with a wrench. i did not feel any metallic object reisiting the turning nor did i hear any metal parts hitting each other, going to retime it by the book tomorow and will post back.

i really wish i could get a seconed opinion though. :confused:

to isolate a rod nock, it will knock at tie same speed as the engine (if that makes any sense)so if the engine ........not nto be corny..........is fireing 4x and you hear only 2 knocks its probably valve train. so if you hear a knock for every time the engine fires its lower engine. if its a heavy deep sound its probably the rods, a slapping sound it might be a wrist pin, and a light ping type is more than likely to be a piston. take a pry bar or any type of metal rod and hold one side to your ear and the other aganst different parts of the motor around where you think the noise is comming from. it will get clearer as you get closer to the problem area. but watch where you are in relation to moving parts, plug wires ect. since you dropped the pan, check the side to side clearance of the rods with a feeler gauge, and take off the rod caps clean off any oil and use a plasti-gauge. also once the caps are off( mark each 1,2,3.ect and alignment....mark all on the same side to ensure they are in the same place as before taken off.) youll know right away if you spun a berring.

as for the miss fire, is the ck engine light on? if so which codes are stored becides p0300? check the vaccume lines. the emission hose for the fuel regulator and evap purge was leaking on my 3.8. once i replaced it(21 bucks from chevy) all was good. sprat brake clean around the usual culprets and the not so usual to find any vaccume leaks. check the oil dipstick too.........this could be where unmetered air is entering causing a lean missfire. check plugwires, plugs. the condition of the plugs will tell you about the condition of the burn in each cylinder. i dont know for sure but if the timing gears arent where they are supose to be the car wount run...or if it does could have a bent valve. well thats what i could think of at 1 am so good luck.
Dave