I just did this over the weekend with my fathers help. The spark plugs are located right on top of the valve cover(whatever you call it) There are 2 coils for the 4 plugs, this is if it is a 4cyl. You simply pull the plugs out one at a time and using an extension on your 5/8 in. ratchet/socket set you can change them very easily, yo will need a 10mm socket to remove the coils to take out the 2nd and 4th spark plug, the recommended gap is .39-.43...took us about 20 mins once we got the right tools for the job...hope this helps...if you have a 6cyl, I can't help you out...
2002 galant , can't find the spark plugs
how to change number 6 spark plug on a 2006 mitsubishi galant
It is most likely your spark plugs and or wire set. All of this is easy to change. There is another forum that explains how to change your spark plugs for your Galant.
You must remove the entire intake manifold for you to have access on the three spark plugs located underneath it. it is advisable that a qualified Mitsubishi technician should do this.
you need to take the intake off to get to the back three plugs...
remove intake manifoled to access back 3 plugs. time consuming but can be done
pcm or crank sencer
Most had a V-6 under the hod, which would mean 6 spark plugs.
When changing the spark plug gaps it is important to remember the gap size. The gap size for a 2003 Mitsubishi Galant 4 cyl spark plugs is 0.044 inches.
if its got a v-6 in it it has 6, if its a 4 cyl. it has 4
My 2002 Galant has not had spark plugs replaced for over 100k due to where they are. Three are underneath the intake manifold. Yes...intake has to be removed. Not difficult now that I know. Lots of bolts and hoses need to be removed to lift the manifold.
make sure the gapping on the plug is correct to what the vehicle needs