Hey guys, I posted in the general forum but wasn't having much luck so I figured I would try in here.

https://my350z.com/forum/maintenance-and-repair/185549-loud-vibration-when-engine-braking.html

The car is a stock '04 base.

Basically, the problem is something vibrates around the engine really bad upon engine braking from high rpm. It's sporatic, meaning it doesn't do it every time. If I push in the clutch, or just wait until the rpm fall low enough, it goes away.

Someone told me it might be a problem with the fuel pressure regulator. Can anyone here help shed some light on the stock fuel system, or help diagnose the problem? I'm going to have the dealer look at it but I would like to be armed with a little more information before I go.

TIA for any information or help.

 

The stock fuel pressure reg is located in the fuel pump assembly, so that is not the source of your sounds. Honestly, it could be just about anything, as noises and vibrations are nearly impossible to trouble-shoot over the internet.

 

Thanks sharif! So I can definitely rule that out.

If I just sit in neutral and rev the engine to redline, it's fine. If I take it to redline in a gear and then let off the gas, as I'm engine braking it's like something kicks on all at once, vibrates really bad, and once the rpms drop to a certain point it kicks off.

Does that help narrow it down any further?

 

My Z has done this since day one. Like you said it doesn't happen all the time, so I haven't bothered to have the dealership look at it. Has yours just started doing this recently?

I feel like the vibration is coming from the transmission becuase I feel it the most through the shifter. After reading your first post, I think I'd better make an appointment with the dealer to have them check it out.

 

Once I started driving hard after the break-in is when I first noticed it. So it's been there all along. I didn't have it looked at sooner for the same reason. The first time it did it, I was like holy sht what the hell was that. But it didn't present itself as a serious problem because it would go away and everything seemed fine other than that. I kind of got used to it doing it every once in a while, but it still bothers me.

I don't think it's coming from the transmission... it doesn't sound like it at least. With mine the noise comes from the front (possibly the front right) of the car rather than right next to me where the tranny is. Any vibrations from the engine or any of the compenents can make their way through the shifter since it's all connected. I think I even notice the steering wheel vibrate too.

I just went out and tried to reproduce it in 2nd gear a handful of times and couldnt do it. I was on city streets and didnt want to get a ticket. I will get on the interstate and try it in 3rd gear. I can't remember if it only happens at higher speeds???