Why is my cylinder 4 still misfiring?

Asked by LeeroyJenkum Aug 08, 2020 at 05:25 PM about the 2007 Chevrolet Cobalt LT Sedan FWD

Question type: Maintenance & Repair

I just changed all 4 spark plugs and all 4
ignition coils and I’m still getting a p0304
code! I need help with this because this is
causing my car to die when I use my ac. It’s
summer time in Texas I don’t think I can make
it much longer riding with the windows down!

1 Answer

18,715

Lots of electronic issues on older cars are caused by loose and dirty connections in the wiring harness and by weak, dirty, broken and loose grounds. Some time spent carefully taking connections apart and making sure they are clean and making good contact may well solve your problem. Also load test your battery to make sure it is in top condition. Modern electrical systems are so sensitive that even a battery that will start and run the car may still not be up to doing 100% of its job. If its 5 years old or older I would just go ahead and replace it.

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