So I've recently got a 08 G35x and the bolt on Cylinder 3 broke so im getting a P0300 code so I'm not sure if that's maybe causing that code to pop up TIA!!
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Probably not, pull and inspect all plugs, use an extractor to get that broken bolt out.

 

Would a misfire cause car to idle at 1k rpm by chance? But also I'm getting p0304 but I have it's a feeling it's cause I put an older coil pack in there but the p0300 I'm not sure what's causing that my mechanic said I have a vacuum leak and wanted to charge me to inspect but I currently don't have the funds so once I do I'ma have him inspect it but also my car doesn't idle weird or nothing it just stays at 1k rpm does jump at all or nothing just stays there and once I put it on drive it drops underneath 1k so will that misfire cause that high idle

 

P0300 just means there's a misfire, P0304 means it's specifically on cylinder 4.

1000 rpm idle is definitely high and usually caused by a vacuum leak. Check out the PCV lines from intake-valve cover-across to other valve cover-back up to intake plenum and make sure they're all tight and cannot be turned easily by hand. If they can be easily rotated then put a hose clamp on those ones.

Also remove and inspect the intake tube for any rips/cracks/tears, particularly at the accordion flexible sections.

 

So I changed the pcv valve but didn't check the lines I'm going to be buying new silicone hoses down the road but I will check them and hopefully it's just a bad hose and also I did have a rip near where they go over on the tb I replaced that one on the passenger side and on the driver side I did see like a crack by the flexing part of the tube but didn't seem to be cracked fully through the other side so can that maybe be it?