Hello, I have a 2004 g35 coupe that has a couple of new problems. Recently, when i went to start it up, it turned on then immediately died. I started it again, and it turned over about 6 or 7 times before starting. On the way to work, I was in 2nd gear and stomped the gas at around 3500 rpms, and It sounded slightly muffled and had less then half the power it normally does. It seems to drive normally in lower rpms. Other times that I press the gas harder, it still feels like something is not allowing it to produce all the power it normally does. Any ideas what might be causing this?

My battery is 4 years old, and has slight corrosion on the positive terminal. I changed it with a new and better quality battery, and it appears to run a bit better but it is too soon to tell if that fixed the problem. I am thinking it is more likely a timing/fuel/air related issue.

 

It sounds like your car is staying in closed loop mode though. Why? I can't say, but I would begin by checking sensors, most notably the o2 sensor.

 

Within the last year (long before this current problem) I have replaced the O2 sensors in the exhaust (motordyne art pipes replacing the cats), cam position sensors, crank sensor, knock sensor, spark plugs, and other things I cant remember at the moment.

Also, im quite certain its not in loop mode, as it is not permanently weakened in power, it varies.