1993 240sx conv injector or sensor problem

[showtime33772]

need help solving this electrical problem1993 240 sx conv replaced all injectors rebuilt 3 months ago also replaced knock sensor, and temp sensor

was running great getting over 33 mpg on the highwaywas driving stopped then restarted engine running rough

all cyl getting spark #4 injector when discon does not change how engine runs,

this did this before at the time i replaced knock sensor about 3 months ago but sometimes the faulty inj would change holes ie it might be #1 or 3 ,4 or 2.

i think i am missing an electrical short somewhere

any suggestion i just love this little ragtop

[Eikon]

If you just had the injectors rebuilt, chances are your ok there.

Start the engine and then pull one spark plug wire at a time, then put it back and move to the next one. Clearly if the pitch of the motor changes when you pull that wire, then that cylinder was working fine. When you pull a wire and nothing changes, you've found the dead cylinder. Could be a bad spark plug, a poorly gapped plug, a bad connect from the plug wire to the plug, a bad plug wire itself... Could be many different things..

Have you ever swapped the distributor cap and rotor? In time the rotor can crack, or the seal around the cap can go bad and you can get moisture in there.

Try squirting wd40 around the edge of the cap. It drives out moisture and helps you get a better connection.

Try those things and get back to us and we'll keep working on it.

Good luck

[DeXteR]

Even though you had your injectors rebuilt, don't rule out a faulty injector. Make sure you check it.

Like Seth said, check your plugs, wires, cap, and rotor too.

In my experiences, unrelated systems tend to fail at the same time to complicate trouble shooting.