I have been trying to solve an issue for about six months on my 2007 G35 sedan. I have 115k miles on the car and since around 90k miles I have noticed a significant drop in power output. I have not done anything to address the problem for while due to other more important things going on in my life. The car has 306HP but it feels like I'm only getting around 200HP. I'm talking about a significant drop in the throttle response. I used to be able to easily spin the tires from a stop, now I simply can't.

The car has no rough idle, no issues starting up, no dash lights turn on. Gas mileage is the same. Exhaust note sounds the same. Idle RPM doesn't change when I stop at a red light or stop sign. The car drives normally.

Here is what I have done so far: Replaced spark plugs at 105k miles and that made a tiny, but noticeable improvement, but didn't come close to solving the problem. I tried adding Techron to my fuel tank to clean the injectors (BTW, I always use top tier gas). I have replaced the engine air filters (once per year). I have done a mass air flow sensor cleaning. I'm thinking of doing a throttle body clean next but I doubt that will do much. And I am diligent about doing all the normal maintenance.

Basically, the car drives perfectly fine but I feel like the engine is only pumping out a fraction of the power it should be putting out. I'm baffled and running out of ideas. Does anyone have any ideas?? Thank you!! Very much appreciated!!!

 

ummm maybe a bad cat, or fuel pump going bad, or maybe throttle pedal sensor going bad. iono just throwing ideas out there.

 

You might want to check your oil pressure to be sure the oil gallery gasket isn't leaking. If it is bleeding off oil pressure, then the variable valve timing advance will not work properly. Typically when this happens, you will get a check engine light, but maybe you are right on the cusp.

Also, you didn't mention which tranny you have. If it's a manual, it could be a slipping clutch, and it it's an automatic, it could be a lot if things tranny related (torque converter, tranny controller, clutch pack, solenoids, etc.)

EDIT: I like hurleyguys' idea about the bad cat. I have had a clogged cat before on another car. It definitely clips the engine output.

 

For a almost 10 year old vehicle, did you ever think of having a local Infiniti dealer hook up their Consult lll and take your vehicle out for a test drive to see what is going on?

Might be cheaper than just replacing parts.

Telcoman