2DC3

It is 2005 Honda civic with 260k miles.
Recently did a tune up and the engine ran smoother but the hesitation at 80+ didn't change. Not sure what my next step should be. Just bought please help!

thisguyaves

Google your codes.

P0300 is random misfire, P0304 is cylinder 4 misfire. Check the cylinder 4 spark plug first of all, then verify good compression and fuel flow.

2DC3

I apologize, I should of been more specific. The codes are P0300,P0301,P0302,P0303,P0304. I've googled the codes and figured a tune up(plugs, coils, air filter, oil change) might clear them up but no luck. After that there are a lot of different diagnoses. I am looking for an efficient order of diagnosing it without throwing a ton of cash into it. I was wondering what my next step should be after a tune up.

P.S I am in no way a car expert but am looking to learn.

thisguyaves

"tune up" on these cars means new spark plugs, verify timing is good, and a valve adjustment. If you have misfires on all cylinders it could be (in order of likelihood with your mileage) a head gasket, fuel pump, or timing issue. After that, you'll have to hunt it down. I personally think it could be a timing issue if your spark plugs look good.

2DC3

I wasnt aware of that, ill be checking that next, Thank you and will post a follow up.

thisguyaves

Pull the valve cover off, get cylinder 1 at TDC and check the cam alignment. Might have skipped a tooth or two.

Tim1959

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There is a detailed troubleshooting procedure in the Factory Service Manual (FSM) for these DTCs (P0301, P0302, etc).
Looking at the freeze frame data is important. I use only OEM (Honda) parts on these cars to avoid problems.