I have a '04 G35 Sedan. It has been in the shop every month for the past 7 months, not kidding! It now is not accelerating like it should, there is a noticeable lag, and when you do (accelerate) the engine starts to hum. The humming sounds like a boat but is only there when you push the gas peddle. Last night the Slip light came on for a second and went off. We just (last month) replaced the throttle body and the brakes. What else could it be?

 

no CEL?

 

you mentioned a couple problems that really dont go with one another. Could you be more specific about the noise? where is it coming from? does it happen all the time or only when you accelerate under load? whens the last time you changed your oil? how many miles are on the car and what maintence hasnt been done yet? how many miles since you replaced the throttle body? did you check the dimensions and make sure its the same size throttle body? if the inlet size is off the engine wont be able to get the required airflow to run the map the ecu is programmed with. check your clearences on the opening of the throttle body and compare it to the stock one. im sure you can find the dimensions on here somewhere (just search). check your fluids. make sure your air filter isnt completely ****ty. The car may still be relearning your driving habits, im not sure how much you drive but this relearn period can last anywhere from 1000-3000 miles so if you havent made it to your next oil change after the throttle body replacement it could still have some learning to do.

 

Are you getting a CEL? Why did you change the throttle Body? Did you do the Idle Relearn procedure?

 

Sounds definitely like a TB/MAF issue.