Hey all, about 6th months ago I bought my first Z. It's a 2006 350z 6mt, and I'm loving it. I'm having a problem though that I can't seem to find the answer to. I've searched and found threads discussing similar issues, but not quite the specific problem I'm having. If there is a thread and I missed it, please simply direct me to it. Anyways, I don't know how serious of a problem this is or what the root of the problem is, so I came here for answers.

When I first bought my Z there were no apparent issues. However after adding an exhaust, Mrev 2, Plenum spacer, and cold air intake, I started noticing something abnormal. When I go WOT the car pulls like it should through 1st and 2nd gear. I can slam the shift from 1st to 2nd and the car just hammers into gear, but when I shift into 3rd at WOT there's a sort of stutter. It only happens in 3rd gear at WOT, and only when I'm trying to shift quickly. If I give the revs even a few extra milliseconds to drop between shifts, it doesn't seem to do it. When it does happen though, it's like the rpm gets stuck for maybe half a second, then the car pulls like normal again. The best way to describe the sound is similar to a car 2 step launching, but right before the car starts backfiring. Not sure if that makes any sense, but it's difficult to put into words. Maybe my car has had this problem since I bought it, and the addition of the exhaust and intake components just made it more noticeable due to the higher sound level. I don't know though, hopefully someone else has experienced this that can give me some insight.

What do you think could be the cause of this problem? I noticed I have a slight exhaust leak at the flange that connects to y-pipe to the cats, but I ordered better gaskets to eliminate the leak. So we'll see if that solves my problem, but I don't think that is the cause. I also have a small vacuum leak somewhere on the passenger side of the engine bay that I haven't been able to find (haven't had much time to fix it). I think it's possible that the vacuum leak could be the issue, but that doesn't explain why my issue is only in 3rd gear. Could it be the clutch? Or could it be the 3rd gear synchro? I've never experienced synchro grind while shifting in my Z, just the 3rd gear stutter when I engage the clutch at WOT. Any ideas? All inputs are greatly appreciated. Thanks guys! -Ryan

 

You should tune it, especially considering all the breathing mods you have done

 

I'm aware I could use a tune, just lacking the funds at the moment. However, I would think if the tune were the cause of this problem, it would be present when shifting into any gear at WOT. Correct me if I'm wrong though

 

you are wrong... it doesnt doing it under normal driving, right? during WOT you are flooding the engine with air, you are running lean. the factory tune cannot compensate

 

You have a lot of breathing mods I am also going to say tune problems are likely. Fixing the vacuum leak would also be a good idea before tuning, the exhaust leak probably isn't doing much as it's after the O2 sensors. An uprev etune base tune might be a reasonable option for the short term for 250$.

I think the stock tune limits the throttle body to 80% in first. My guess is that you would have the same problem going WOT 3-4 but you shouldn't be doing that on the street.

 

Sounds like transient lean spike on throttle tip in. Log AFR with Cipher if you wish to confirm. As others suggested, a tune is likely needed. Try to find someone that has experience with this platform and UpRev.