It started to misfire 2 days ago. So I change the spark plugs and turn on the car and it still misfires. After that, I decided to install 2 new coils on the driver side, after I turn on the car it still misfires. I check the compression level and it wasn't high enough so the car turned off itself. So I decided to put the two old coils back in, turn on the car and I do not hear any more misfires ever since the whole day today and it runs well after. But I'm still paranoid about if the engine starts to misfire again (It only has 58k miles). What should I do at this point? should I take it to the shop and see if they can fix the compression? Valves? or Piston? I need help please to seek an answer, please.

 

This post makes very little sense, can you clarify please? Are you checking compression with the engine running, if so, what are the numbers? The car shut itself off while you were checking compression?

 

Yes, the car shuts down while I was checking the compression and it went to 50-70 (with the new spark plugs). I put on the old coils back on and then it starts to run great again but I did not hear any misfire the whole day. Since is already running great again, I'm still paranoid about it. Should I still be worried? Should I still take it to the shop and let them diagnose it?

 

Again I’m confused. Spark plugs have no affect on compression, and are not even installed when checking compression. Also, checking compression is usually done with all the plugs removed, and just cranking the car over, not running it, so I’m really not sure what to tell you at this point. Maybe taking it to a pro would be best.

 

can you even check compression with the engine on... you check it with the starter spinning the engine over.

I'd assume it's caused by the coil packs, always where all my miss fires come from.

 

so i’ve been having this p0300 code on my 2003 350z for quite some time now, i’ve gone through the works replacing the coils(z1), plugs(ngk), and injectors(bosch). also gone through and bought new gaskets for the plenum even did a valve cover job because it was leaking oil, it was also leaking a bit into the plugs at least i think i never saw a puddle of oil in the tubes but when i pulled my plugs before doing the valve covers i saw some oil on the threads and o ring of the plugs. i also have freeze frame data of my fuel trims being excessively high, i’m at a loss here guys if any one has any ideas it would be greatly appreciated!
i ended up replacing the valve covers and still a misfire but no leaks!
DTC_CNT : 2
FUELSYS1 :CL
FUELSYS2 : CL
LOAD_PCT :18.0%
ECT (•C) : 98
SHRTFT1 : 6.3
LONGFT1 : 9.4
SHRTFT2 : 2.3
LONGFT2 : 9.4
RPM : 650
VSS : 0
SPARKADV : 16
IAT (•C) : 34
MAF (g/s) : 2.75
TP : 1.2
O2B1S1 (V) : .280
SHRTFTB1S1 : 7.0%
O2B1S2 (V) : .190
O2B2S1 (V) : .090
SHRTFTB2S1 : 3.1%
O2B2S2 (V) : .280
thanks for any help! i know you guys are the Z experts