Hard start, misfiring, bad fuel mileage, shakes at an idle on 1995 Pontiac Sunfire

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Over the past month my car has been needing a little extra loving to start. Occasionally you can start it easily without pressing the gas but rarely. It cranks for approx 5-10 seconds before it starts and immediately begins to shake and the smell of exhaust is DISGUSTING! I recently replaced all of the fuel injectors and had them tested before putting them in, but that is about the time i started having these problems. On top of this it's misfiring on the fourth cylinder and and only going about 2/3 as far on a tank. I use fuel injector cleaner and this has done a minimal amount of benefit. I'm a poor student and am wondering if you know what the source of my problem could be and if so is it worth it to fix?
(2) Answers
Maybe be your ignition coil pack housing as you are not firing on all 4 cylinders. Buy a GM version to replace as the aftermarket do not last more than 60 days.
If your 1995 Pontiac Sunfire is misfiring on the #4 cylinder that is were you should start looking for your problem. The misfire could be caused by an ignition system, fuel system, or engine mechanical fault. If the problem started with the replacement of the injectors that may be a good place to start. Some basic diagnostics will be necessary to determine the cause of your engine misfire.