hey folks. I replaced both my spark plugs and wire about 5 months ago. I just recently checked the gaps on them and reinstalled them. The spark plugs are tight along with the wires. however every so often, when I am in 5th gear and going up slight inclines, my check engine light will start flashing at me. When i get the code read it brings up a misfire in cylinder 3. It doesn't feel like its misfiring though. It only flashes in 5th gear when going up inclines. Is this a fuel injector issue? the CEL eventually goes away after a day or so. Has anyone else had this issue? Am I losing compression in that cylinder?

Imo, sounds similar to an ignition coil starting to go bad.

Slight to bad misfire when under heavy load (going up a hill in OD)

any oil on the plug wire boots?

 

can you swap wires around to see if the problem folllows that wire?