Hi everyone,
I recently had my “Service Engine Light” come on, Sunday to be exact. I went through my normal procedure of checking the fuel cap and drove several times to no avail. So today I ran by Autozone where I got the P0302 code. Now I realize I could go in for a tune up, but I’m a college student and just spent all my money on books so I’m looking for some DIY solutions before I lay down any large amounts of money. From reading different forums and sites I haven’t been able to get a clear answer on where to start. As for a bit more background, I filled my car up with gas on Friday, the light came on Sunday and the car will shake on initial idle of the car. Thanks for any and all help. PS I’m a young lady so “Lehman Terms” are greatly appreciated! 
That 302 code is for a misfire on cylinder No. 2. Normally this would be caused by a faulty spark plug and/or coil.
Tune-up is kind of a misnomer anymore so you could have a set of spark plugs installed to see if this problem goes away. Ideally, while the plugs are out a compression test should be performed to make sure there is no mechanical fault with the engine that would cause this misfire.
If compression is good and the problem still exists then it may need a coil. Another possible cause of a misfire could be a faulty fuel injector but this would be much rarer.
Hope that helps.
Yes this helps. I just talked with a friend who works at a Cadillac dealership and he suggested switching the 2 and 3 coil packs and getting it coded again to see if the codes to cylinder 3. So I think that will be my first step!
Thanks!
Good advice you were given as you do not want to buy coils unless necessary. They’re at least mildly expensive.
Keep in mind that aged spark plugs can kill coils too.
Thanks! Good to hear I’m taking things, somewhat, in the right direction. Any suggestions/ideas on buying a fuel treatment 1st?
Pass on any fuel treatments. It’s a waste of money.
Ok. Thanks again! Fingers crossed things end being an easy fix.