Another update: Still no consistency. The weather cooled down and the car was behaiving quite well until today. Nothing drastic in the weather so it may have just been luck. Still no oil pressure gauge but I noticed upon start up the a/f gauge stays at 14.x when it works. A few seconds after start up, the gauge will drop to it's lowest, 10, and that's when I start having problems. After driving for a little bit it clears up. Turned the car on and off a few times and I think it only started normally once.

UPDATE: Oil pressure is normal. Our next focus is the fuel pump. I've also noticed when the car is down to 3-4 dots of gas left is when problems tend to be more predominant. Car also runs a bit rich sometimes in 6th gear

Keep the updates coming. If I can't figure out what's causing this issue in the next few months the G is going up for sale.

F Nissan right now so pissed off at this car

update: no conclusive results. It's clearly an airflow issue. potentially fuel pump, throttle body related, or even a bad map (doubtful).

On start up a/f gauge drops to 10 but car spits out black so I know it's rich. If I was as rich as my car I could have had this solved by now...

@Business Kat. It sounds like you're sucking air in from somewhere. Have you removed, cleaned, and re-sealed the TB's intake manifold, and lower manifolds?

I had an issue similar and the upper manifold actually was cracked and air was escaping/entering when it shouldn't be. This is past the sensors so they never picked up on it.

I ended up replacing that as well as my fuel pump, and have been problem free.

Update: I'm hoping it's finally solved. Bad fuel injector

My car started to sound like a busted old mustang/helicopter. A code finally popped up and we figured out that the fuel injector in cylinder 5 stopped working. Had it replaced, it's been 2 days now, and I haven't had any problems with it. I'm still getting 5psi boost vs 8 but I'm pretty sure it's from the same part that leaked before. I will definitely update again if this was the problem.

I'm going to be SO MAD AT STILLEN if this was the problem. First, they sent me the wrong map when I got the car and told me I'd have to wait 2 weeks before they could send me another one. Then, the small plastic part that was crushed and was causing my air leak "wasn't covered" by the warranty and they wanted me to pay $15 shipping for like a $5 part. AND NOW a faulty fuel injector???? I spent thousands trouble shooting and Stillen didn't help me through any of it. When people on the forum said stillen aint what they used to be I should have listened. Done venting - stay tuned for more updates

I hope with the new injector you can solve that problem man! :tup:

It's only had 2 episodes since the fuel injector was swapped and they were rather short. I think the bulk of the matter was a bad fuel injector from Stillen as well as another plastic piece that was crushed a few months back from their kit.

Momma said if you don't have anything nice to say, don't say anything at all. BUT I want you guys to know that Stillen absolutely screwed me with all this. They sent me a wrong tune day 1 so I couldn't even drive it. I had to get it towed for a new tune. Then they said the plastic piece isn't covered under warranty after I had spent hundreds trying to figure out what the problem was. Once that piece was replaced their fuel injector died which, guess what, isn't part of the warranty.

Never using stillen for anything ever again.

Damn bro sorry to know your story.... Its really a PITA when you cant not solve issues like this by the easy way :shakes head:

Update: Car went into limp mode. Was fine after a restart but check engine was still on. Stalled once. Limp mode 3 more times. Made it to a mechanic who cleared the code P1239 and the car is normal again. I have to drive ~100 miles tomorrow so we'll see what happens. HOPE I DON'T MISS MY APPOINTMENTS #overit #thxstillen #nevermodacar #saveupforamaserati #oragtr #justdontmod

Update: Code was the tps. Did some research and apparently the tps sensor stillen provides with their kits have a little bit of a reputation for going bad. Unplugged it, checked the cable, it had power flowing, plugged it back, cleared codes, didn't go back into limp mode. But now we're back at square one where on startup is has a panic attack and then acts normal. Sometimes while driving it'll go super lean as well but usually letting off the gas and letting the car reset for a second cures it.

Ya'll were right. It may be too early to call it but I think we solved it!!

Stillen makes a very high quality throttle position sensor extension that comes with their kit. The technology in this sensor is incredible. It's able to absorb heat and far beyond any cable I've ever come across.

Sarcasm aside, the sensor overheats and will start with false voltage readings and ultimately will cause the car to go into limp mode. This is why idle RPMs go wonky, random cuts in power will occur, and why the cars will go into limp mode.

Someone at Uprev had the same problems as me so they were able to fix it pretty easily. I can't believe this $40 cable and a $5 plastic elbow join cost me thousands in damages and repairs. Stillen told me the plastic peice wasn't covered under the warranty and when I contacted them about the TPS they said the warranty was only good for a year. Can't express how dissatisfied I am with Stillen.

I'll update again but I already can tell there's a massive difference driving it.

So a bodgy throttle body harness extender was the cause?

Hey guys, unfortunately posting back in this thread as i have "the same" issue with hesitation between 2.5-3.5k rpms again, except this time cleaning throttle bodies has not worked. I also cleaned the maf sensors, air filters are clean, reset ecu, checked and "reset" brake switch, checked for intake leaks, using same 93oct fuel as always, oil temp is good and in operating temps when this happens, recently changed engine oil and its topped up and drove the car a few days before this and all was good. In other word, im frickin' stomped!

Rain has been pouring here in PR the last few days but i havent taken the car out much, plus no flooding in my area.

Taking it tomorrow to the dealer to see whats going on. :confused:

Update: took the Z to the dealer and as expected, they dont know what the hell is wrong with it :shakes head:

I told them what i had done so far as inspecting, cleaning, etc.

They asked for two more days to see if they can find the problem, lets see what happens :ugh2: