Hey, Guys, i've been lurking in the forums and reading up as much as i can.

I've had my 2009 G37x for 1.5 years now. First 6 months were great and the car was running really well. Then i moved to a city with a bit more traffic than usual. This when the transmission started acting up with rough downshifts and overall lag.

I read up on the reprogramming and took it to the dealership for a reflash. Car was very smooth for about a month after the reflash and TCM relearn, then started acting up again. I took it back and they keep telling me that its on the latest update, however they wont tell me which update itis on.


Now the Issues that i need help with:
1) Manual mode is very rough. Before, i was able to downshift from 4-3 and 3-2 above 2k rpms, now is very rough and the car sometimes jerks during 3-2 down shift. And 1st gear always results in an audible clunk and sudden engine braking when letting the car coast to a stop without down shifting (does the same when down shifting 2-1 at any rpm).

2) Weird Idling. In D and DS, the car can be smooth...but only when the AC is on (and light traffic). When the AC is off, letting go of the gas results in the rmps suddenly dropping below 1k, then slightly bouncing back up. The car also seems to shift before 2k rpms sometimes resulting in being in 5th or 6th gear while going 35mph. Stepping on the gas just bogs down the engine ...and sounds absolutely HORRIBLE with muffler delete. Also, when the AC is off coasting down-hill makes the idle surge up and down.

Im thinking, maybe a vacuum leak is causing the weird idling, but not sure how id go about finding in it, and maybe a transmission drain/fill may help the rough shifting


The car currently has 85k Miles and and gets Penzoil synthetic oil changes every 6k miles.
Mods:
Mishimoto post maf tubes
AFE filters
BB Grounding Kit
Muffler delete
Hypertech (only the 0-60 restriction applied)
18x8.5 wheels with 245, 45 Tires
25mm Rear Sway bar with PU bushings


Sorry for the long post, any input would be appreciated. Thanks in advanced

Here is couple pics of the car:

 

What is that.....?

 

Hypertech Tuner Error - Hypertech
You can use it to apply a canned tune and remove the 0-60 throttle restriction our cars come with from the factory.

The tune works best with stock cars.

 

Not sure if this will help with everything, maybe not with the shifting but I had the same sort of rpm dipping and cleaning the throttle bodies fixed that. The car ran much better afterwards. I'd say try that and see what happens. It's relatively cheap and good to do either way, especially if it hasn't been done at your mileage. Mine had over 80k as well and it did wonders, car ran better (could've been the placebo effect) but the rpm dips definitely went away completely, hth
Oh and the mafs won't mind a cleaning as well.

 

Had a shop clean the throttle bodies approx 15k Miles ago, they're probably due for another cleaning since i've been driving a lot since then.

Do you recommend any specific method or cleaner for the MAF's? I've been reading a lot of conflicting info about cleaning them, so i haven't given it a shot yet.

 

I just took them out and sprayed them with the maf cleaner (the aerosol can will specifically say MAF cleaner) and let them air dry. Nothing much to it but I haven't really read up on it too much. Figured that would do it. I shouldn't have cleaned them along with the tb's to see if that alone would have made a difference. Sorry you're going through this crap, it definitely can be frustrating. Did you see a difference when the tb's were cleaned? It wouldn't hurt cleaning them again but after 15k I can't see that being the culprit.
I've never heard of the hypertech thing, maybe try taking that out and see if that does anything.
And yes, I'd change the trans fluid for sure. Another thing that's not too expensive and should be done anyway. My reasoning is doing the relatively inexpensive maintenance items first, then move on to bigger issues

 

+1 there are some vids on youtube..

 

Just got and oil change and trans fluid change (drain and fill) done at a Nissan dealership. The car feels smoother, but could just be placebo effect, i only drove like 2 Miles in D. Ill have to take a longer drive later on today to test everything out

Upon closer inspection on my invoice, it says they used Matic K fluid!

What is the difference between Matic K and Matic S? and did they just mess up my trans with that fluid?????

I tried searching about Matic K, didn't find much info

 

how much did they charge you?

 

For the Maf, be careful with it. I hear that you should take off the negative battery cable. Be careful with the stuff, I haven't used it in a while. Do not touch the wire!!!




For the Throttle Bodies, remove the battery cable again, remove your silicone hose and spray as instructed.





K Matic is the old stuff S Matic is the new stuff. Amsoil is the better stuff.

Trans Fluid, I recommend going to XDP - Performance Parts & Race Team Get a 2.5 Gallon Bottle of:

http://www.xtremediesel.com/amsoil-f...ion-fluid.aspx

 

Ended up taking it back to the dealership the next day. Apparently their billing dept mixed up Matic K with S. Spoke to the tech and he assured me he filled it with Matic S.
They charged me $168 for the drain and fill

Overall the trans does seem smoother, i also installed paddles. its nice being able to downshift without going into full manual mode

Im hoping to clean the maf and throttle bodies this weekend