So i started up my 2005 Nissan 350z Touring Edition and the RPM's immediately dropped very low (near 300ish). I did not get the usual roar of the engine instead just got a sputtering sound. I pressed the gas to make the RPM's jump and when i let go they stopped at their normal spot. I got it up to about 10MPH and the engine just began shaking and shuddering so hard the whole car shook. I immediately pulled over and cut the engine off. I turned the car on again and was met with the same low RPM's. I popped the hood to try and see if i could locate the problem but by that time it was gone. The car drove afterwards but sounds off, like something in the engine just doesnt sound right. I've been having the low RPM's for a while now but this is the first time i encountered the shuddering. Any idea how to fix this??

Sorry you're having a problem with your Z, but I'm glad you found us!

The first thing to do is to see what the car is telling you. If you haven't checked for error codes with a scanner that's where you should start. If you have checked post up what you discovered.

Welcome to NICO!

Took it to Nissan for a diagnosis. Nissan said it was a busted Radiator Fan Assembly. I replaced this part and the problem reoccured. Took it back to Nissan and they suggested a Throttle Body cleaning and a Idle Relearn. Throttle Body is less than a year old but we pulled it apart and cleaned it anyway. Did the Idle Relearn procedure (turning car on and off and playing with the gas pedal). Problem is still persistant. At this point i almost question if bringing it to Nissan again is worth it cause they seem to be grasping at straws at this point.

Edit: I only have the RPM issue after the car has been driven enough to get the engine temp up. Engine temp stays below the halfway marker thanks to my new OEM Radiator Fan Assembly and a Volant Box Air Intake. When i originally took it to Nissan my temp was about 3/4 of the way up. This is how they found the Radiator Fan Assembly was busted. Temp stays down now but the low RPM (around 300ish) comes back every now and then.

I am now experiencing a new issue. When slowly cruising up to 60mph, the engine seems to have trouble shifting into 5th gear. When sitting at 60mph my RPM's stay around 3 1/2k in 4th gear. Playing with the pedal decreasing and increasing speeds forces the engine to finally switch to 5th and drop the RPM's to around 2-2 1/2k.

Skip 5th and go to 6th. Seriously the close ratio box on these cars is a waste, I skip gears often seldom do I use 5th. Check the trans fluid, might be somethign as simple as low fluid if not it's likely a bad synchro meaning trans rebuild or replace.

Sounds like camshaft/crankshaft position sensor issue.

And regarding the shifts, sounds like the OP has an automatic based on his description on playing with the load via throttle to get the car to shift.