I have a 2003 G35 Sedan w/ 145,XXX miles on it. We have had the car for about 10 years and not had many problems with it. The fuel pulse damper, the cam position sensor, an oil leak, and for the past few years it started shaking when you would start it up. The car would start fine, but it would shake a little and smoothen out. It could sit for a week and when you go to crank it would fire right up. Then it could sit for a day and shake when it starts up. It does it at random times and has gotten worse the past few years. This morning I go to start it up, and it cranks right up, but its shaking and knocking like a piston is about to come out of the block. So I shut it off and let it set for few. Then when I go back to crank it again it wouldn't start. The starter is spinning over fast but the motor wouldn't fire. It took me about 5 times to get it to start and I had hold the key down for about 10 seconds each time. Then it slowly started up. The shaking and the knocking was gone too. I drove it over an hour to work this morning too and it ran fine. It is also not showing any codes.

I dont know whats going on with it. I would like to fix it or at least figure out what is wrong but the wife is wanting to upgrade to a G37.

 

Look up cam position sensor.

 

The one time that the cam position sensor went out had similar symptoms to what is going on now. Wouldn't it throw a code though?

 

Still worth a check. When mine were going it didnt throw a code for a long time until it really failed. I think it even went into limp mode before i got a code for it.

 

I finally got a chance to replace the cam position sensors. So far so good. I did notice that on the driver side sensor, the connector was soaked with oil. Like the valve cover gasket is leaking again. I don't know if that would have caused the sensor to malfunction or not though.