Wireing diaghram for 2000 galant 4cyl coil pack

backfiring is ignition when an inlet valve is open. from what you have done I suggest checking the firing order as there may be a crossed HT lead or a coil pack on the wrong plug.

it could be a broken wire going from ECM to the coil

Try switching the ignition coil with the other coil and plug it in and check for spark again. If it works in the other coil location, then you need an ignition coil. Your engine is bad for valve cover gasket leaks which deteriorate the spark plug wires, so if you are going to put in plugs and wires with the new coil, I would recommend replacing the valve cover gasket and spark plug tube seals(included with the valve cover gasket set).

change fuel filter- if this does not help the next idea would be to get the catalytic converter checked out

Have the ignition module tested, if thats good then try a crank sensor,

check to see if your firing order is correct

Hello there:
if you have replaced the coil pac you may want to remove it again and make sure there is no moisture or corrosion then if and still have nothing check the crank sensor and the ignition module i just replaced mine after several weeks of troubleshooting and now it is fine
and finally and hopefully this is not your problem is the ecu or electronic controle unit this is the first line of the ignition system and the most important it tells the coil pac to fire and tells which one to fire and when this can have part of it be bad and still have other coil pacs to fire ok

You must have bad ignition wires. The high voltage electricity must be leaking out of the boot(s) and arching from the moist air surrounding the coil pack.
Use a spray bottle filled with tap water. Set the nozzle to mist and not stream, you want to have a misting effect. With the engine running, spray at the area of the spark plugs, wires and coil pack. Do this in a dark area so you can easily see if any arching is produced. Observe while spraying water if the engine starts to run rough. If it does you definitely have an electrical leak and need to repair or replace that part. Some people apply JB Weld epoxy to a cracked ignition coil pack housing, I would just replace the coil because it can cause misfiring of a cylinder and ruin your catalytic converter. For a 2.0 AEG engine it would cost about $70 for the part. If it were the ignition wires, they usually cost the same price.

if the other coils are functioning, then voltage to the coil pack is ok. removing the spark plug wire from the suspected bad coil with no change in engine performance is a reliable procedure to check for a bad coil.

there is none,it has coil packs and a crank sensor,they are behind the rear of the motor near the firewall down low,and a pain in the *** to change,