I notice that the engine speed seems to 'hang' on my 2006 350z 6MT when I blip the throttle and when I upshift through the gears. The tach just kind of hangs at the engine speed that it's at when I put in the clutch, and then it slowly falls back toward idle. If I am upshifting, I have to either wait a couple seconds to engage the next gear in order for the revs to match (i.e. shift very slowly), or if I want to shift quickly I let the clutch pedal out and let the driveshaft+clutch yank the engine quickly down to synchronized speed.

Neither of these are acceptable solutions to me. Is anyone else experiencing this, and is it something that can be remedied? I recently installed an UpRev tune (e-tune) which did not change anything, and this occurred before flashing the tune onto the ECU as well. The condition has not changed....no better, no worse. I was hoping the tune would take care of it but it has not.

Any input would be appreciated. I found one thread with instructions on resetting the throttle body position, and I tried to do this but was either unsuccessful, or worked but did not solve this particular problem.

I'm at a loss...please help!

 

..bump..

 

What mods / filtration do you have?

 

I have the same engine.

I just replaced the flywheel with a "light weight" 17lb ACT flywheel. The stock dual-mass flywheel weighs 28 lbs! After the swap, throttle response drastically improved just as I had hoped. Not only does the engine revs increase dramatically faster, but more importantly the RPMs dropped off immediately.

Here is the thread I posted to compare flywheels.
https://my350z.com/forum/engine-and-...l-tonight.html


I know that in a lot of other vehicles, the Idle Air Control valve plays a big part in what you're talking about, for fuel economy / emissions reasons. I do not think that our engines have an IAC because of the fly by wire throttle. My best guess is that there is nothing wrong with your engine and you are just experiencing the ridiculous rotational inertia supplied by the 28lb flywheel.

EDIT: I just noticed your post count, you probably already knew all this. LOL

 

Engine mods are as follows:
JWT Popcharger intake filter
5/16" plenum spacer
MREV2 lower plenum
UpRev tune (91 octane)
Invidia Gemini true-dual cat back exhaust

Very interesting! I hadn't thought about the flywheel mass. Conservation of momentum, eh?
My post count might be high, but most of my posts are nonsense : )

 

Any update on your issue Sry110? My Z has been showing the identical symptoms the last 2 days.

 

It's still doing it. Car is driving super sluggish too. Not sure how to go about diagnosing. Last I checked the ECU had not thrown any codes.

 

Might look for vacuum leaks. It's just a guess, but unmetered air could cause revs to hang and sluggish driving without throwing codes.

 

Any easy ways to check for vacuum leaks, or is it just checking every tube connection in the intake tract?

 

back in my high school honda days we used to use starting fluid. we would spray it along all vacuum lines and if the rpms would increase then that was the hose that had the leak. I don't know if this is an acceptable way of checking this on a vq35 though, wouldn't want to screw anything up.

 

Carburator cleaner is safer to use but the response is less noticeable. In this case, the engine rpm would drop if cleaner is ingested.

 

My 06 does this to a certain degree also. I have the JWT flywheel and I guess it does help a bit, it doesn't fix the issue. My symptoms are only present in the higher rpm range. When I drive on the street and press in the clutch/let off the gas above 3500 rpm there is a noticeable lag with regards to the rpm's not dropping down immediately, but it does shift into gear without issue. At the track pushing all the way to redline, I experience the same delay with the rpm's falling or lack thereof, only now it gets difficult to upshift into gear. I have to be rather patient with it, and it has caused me blow shifts here and there when I'm not.

It seems to me it's almost as if this is a computer programming phenomenon. I have read that some cars "Rev hang" on purpose to benefit emissions somehow. Not sure how much weight this holds. I'm going to talk with my Uprev tuner about the possibility of having this tuned out of the car. Again I could be way way off though.

 

Those were my thoughts as well. Usually controlled by an IAC, but we don't have one since it's fly by wire throttle. I'm sure somebody on here has dealt with this during their tuning and I'd like to hear from them.

Did you have a chance to talk to your tuner yet about this?