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1998 Mercury Villager Trouble Shooting Help Needed Please


I am a complete noob to diy mechanics and have a very limited knowledge, tool set and budget.
Please keep this in mind in your replies.

Yesterday, i changed the spark plugs, spark plug wires, mass air flow sensor, air filter and replaced the in and out take coolant lines in the throttle body.

Before yesterday, i got random misfire codes that would clear and return, i have no a/c, i believe the thermostat needs replacing as the van runs hot after a while of running and quickly when idling and the upper radiator hose is hot. The van’s idle is rough to the point that some one else turned up the idle so it would stop stalling so frequently, especially in reverse. it stalls very very rarely now.

then a few days a go i got a knock sensor code that clears itself and then returns.

a friend changed the distributor cap, and noticed some melting and corrosion, hence the spark plug and wire change. this friend also pulled the wiring harness for the front 3 injectors while it was running. the one on the far right created no audible engine change (also this spark plug was immaculate compared to the others), so he said it is bad (or is my friend a moron?)
i had also noticed a coolant hose that would spray coolant when really hot.

so yesterday i tackled the above.

in the process of doing this i had to rip the other coolant hose to remove throttle body, i replaced these with a self cut piece of 1/2 heater hose. after removing throttle body, i realized i needed a gasket. so got one of those.

a few notes:
i used antisieze lube and dielectric lube on spark plugs, thread and ceramic respectively.
the mass air flow sensor is used.
i cleaned the throttle valve with brake cleaner (non chlorinated) because it was nasty!
i did not remove the cables attached to throttle body, just moved it out of the way while working.
i hand tightened everything.
there were 2 skinny hoses i disconnected, one with a metal tip that went in to the large rubber air intake hose, and one that ran into the throttle body (this hose ripped like a 1/4 inch off it seemed long enough, so i did not replace).
i disconnected the large air intake hose at 3 spots with pipe clamps.
i disconnected 3 wiring harnesses 2 at throttle body and 1 at mass air flow sensor

now, it seems the van is running smoother while getting gas, but rougher when idling.

please please please, what did i miss? what would be causing a rougher idle?
i am now at work, i will not be home till around 9 cst. so i cannot check anything.
the van did throw another code, but i have not checked it yet.

thank you for any help you may share!!!

Your friend is right about the super clean spark plug on the cylinder that appears to have the misfire. It is an indication that coolant is getting into that cylinder and steam cleaning the plug.

The coolant could be getting in through a breach in the head gasket or in some cases, a breach in the intake manifold gasket.