VQ35DE
I had the same problem ,,,
The STORY : I fixed a race air filter and every thing was OK, then I washed under the car's hood, then the problem starts ..
Bad mode in the morning, good mode in the evening ...
I took the car to many places to chek it, and they said that the computer did not show any problem ...
one day I removed the switch of the air sensore when the engine was on, then the engine starts vibrating then become off,
When I start the engine, the "CHEK ENGINE" lights ... Now I went to the tech. to chek the engine with computer, then he saw the error code and he reset it after I return the original air filter...
now my car is in the good mode ...
I hope that you get an idea from my story