Pissed off with motor, want to change

sorry but no ones mention it could be a bad spark plug

he said every thing was find until he wahs the engine compartiment
thats right???
look like a bad spark plug to me or bad cap

run pretty good until he load the engine
look like a bad plug to me

is it a dual exhaust car?
ask someone to look on each side it back fire (driver or passenger)
so will know on wich side you have a problem
`
after that you only have 4 cylinder to look at
does it have headers??

if so take a plastic cap from a spray paint
rub it on the headers tube it will show you wich cylinder doesnt fire all the time and cause the back firing the tube will be colder and the plastic cap aint gonna melt as fast

sheap laser thermometer if you prefer

a crack spark plug will do the exact same problem as he have

if you wanna go a little further after looking at what I just said put salt in a spray bottle and hade water to it

at dark spray the wire and cap with this mixture I dont know why putting water and salt conduct electricity much more and you will see if the wire or cap are faulty

alwais begin with the cheaper parts and easiest test

aint cost a bunch and make quick test

my 2 cents

Bob