The car went in for a tune up , afterwards I started noticing that it ran rough and was getting codes. Finally have it down to one code that pops up repeatedly which is #4 cylinder misfire . I replaced the plugs again , and moved plug wires around and even put a new ignition coil on. Still getting the same code and I am wondering if it might be the injector starting to go bad, I have 259k on this engine and it doesn't use oil or run hot. The car will sometimes go 80 miles or so before the check engine light comes on and other times just a few miles and it comes on . The engine is a 1996 2.5l and has run fine before all this started.