I've got a 99 sunfire that has a terrible time getting going, has a hard time starting (sometimes), and has a rough idle. The car sat for about 2 years before I bought it but since then I have changed the plugs, wires, air and fuel filters, oil and oil filter, and used about 5 bottles of octane booster, fuel injector cleaners... None of which have helped at all. Check engine light is on and a was told there is a misfire on cyl 1. Also there is about 189,xxx miles on it. Does anyone know what I can do to fix this. I really need this done soon as I will be deploying in may and will be selling it when I get back. Any insight would be helpful. Thank you in advance and have a great day!

Which engine?

Did you do the work, or did others do it?

What are the codes?

If you have a misfire, how do you know it's #1?

If you changed plugs and wires, have you checked coil output and compression?

Check for vac leaks?

check if the fuel pressure regulator is leaking?

It has the 2.2L engine.

I did the work on everything but the fuel filter and i'm not sure what the codes were, when i had the fuel filter replaced they checked them then wrote down that there was a misfire on cyl. 1. I have not checked the coil output, compression, vac leaks, or for a leaking fuel pressure regulator.

Has the engine has a compression test done?. How about the fuel pump Psi test?. Maybe a coil pack has gotten weak.