I've had this misfire on my 2002 gs300 I have new spark plugs and wires and DENSO ignition coils they are all installed correctly ,my compression is good , my fuel injectors are fine, but the strange thing is when I run the OBD reader one day it says cyl. 1,2,3,6 are misfire the next day only cyl. 5 is misfiring the next time I run the scanner it says cyl.1,2,3 are misfiring then there will be another day saying all cylinders are misfiring ,my car runs fine no stalls or anything scary like that and I've been told by my long time mechanic he doesn't feel a misfire neither ,I've been told by people and another mechanic that they don't feel no misfire like when they put the car on drive and hold the brake and hit the gas at the same time to feel if theirs a misfire ,please help ,and would it be possible that my ecu can cause a misfire ,I've been told something about that I can maybe have something electrical that's wrong NEED HELP

 

even though my gs has a v8 in it, I encountered the same thing with mine. but it only did it when first started and would set misfire codes randomly and never misfire when warm. luckily i have a air fuel ratio gauge in my car for monitoring air fuel bc of my supercharger. whenever it would set misfires codes when first started, the air fuel ratio would be too lean at about 16:1 which when first started on cold motor should be richer at 12:1. anyways, long story short, my fuel pump was on its way out. not sure why it would only do it when first started but it hasnt done it since.do you have an after market air intake? also, disconnect your battery and touch the cables together for 30 seconds than leave them disconnected over night. see if that helps.

 

so your saying it might be your fuel pump and no I have a stock intake and its functioning correctly I just put a brand new air resonator ,so it can sometimes be the fuel pump ? I tried looking into that a while back

 

did you disconnect the cables and hold them together like i suggested?

 

check your wires connection,it will throw intermitent missfire if bad special at fuel injectors,again see vacuum leaks

 

check your ecu