engine knocking,black watery stuff coming out of exhaust

What do you mean " the tip was shaved off"

let me know on that if you would.

The 0300 code means random misfiring

Sounds to me like a vacuum leak or a EGR thats staying open all the time.

your going to have to check the Vacuum first.

On most engines the vacuum should be steady between 16 and 22inches.

A lower reading usually indicates a vacuum leak, but it might also indicate an exhaust backpressure problem (such as a plugged catalytic converter).

A vacuum reading that gradually drops while the engine is idling almost always points to an exhaust restriction.

An oscillating vacuum reading usually indicates a leaky valve or worn valve guides.

If the engine is experiencing any of the following symptoms, a vacuum leak is probably causing the P0300 random misfire DTC:

A rough idle or stalling;

A large vacuum leak can lean the air/fuel mixture out to such an extent that an engine will not idle at all. An EGR valve that is stuck open at idle can have the same effect as a vacuum leak.

The rough idle in all of these cases is caused by "lean misfire." The fuel mixture is too lean to ignite reliably so it often misfires and fails to ignite at all.

You can check for vacuum leaks by squirting carb cleaner on the hoses and see if the idle changes, if it does there's a leak there.

Try this and let us know.

Tinner.

Awfuly new to have such symptoms...the black watery stuff can be 3 things:

-Fuel from being unburnt...maybe a coil or spark plug is bad and not firing or not firing properly or perhaps even an injector is malfunctioning.

-Coolant...it's leaking into your cylinders through a crack in the engine block or through your seals...not good. That'll lead to full engine failure quickly.

-Oil...less likely because your say it's watery but still a possible fluid. Could be caused by a large number of things.

IF you're tight on money, check the spark plugs and make sure they are all firing properly...if those check out I'd say you're likely out of luck and need to go to a shop as Matt and oldturkey03 said.

PS- Is your check engine light on? Can you get an OBD II code from it???

P300 is a random misfire and P301 is a misfire on cylinder one. If the spark plug you replaced was the number 1 cylinder then do a cylinder leak down test & a running compression test. Compression test all cylinders and compare. If two cylinders next each other have low pressure, the head gasket is probably blown. If the black liquid coming out of the tailpipe smells like coolant, that's definitely the problem. If it's just black water, you're most likely ok if it hasn't been run like that too long. Test your engine vacuum. If it slowly falls at idle, you have restricted exhaust and it's most likely the catalytic converter, since raw fuel has been going into it, burning up the converter and sending the pieces into the muffler.

Black water can be caused by a malfunctioning electronic choke