7AT super slow shifts and throttle response

T-Rex57

Hey all, I've searched the forum but not sure the existing answers solve my particular problem

Slow shifts have always been a problem with my car, pre and post UPREV tune, but it seems to be getting worse.

About 9/10 times the car shifts very, very slowly in most conditions, in D or M with or without VDC on (though there seems to be a slight improvement with VDC off). It doesn't matter what the ambient temperature is, in traffic or highway conditions there seems to be a general utter lack of throttle response. Merging onto a highway from say 60km/h (37mph) to 100km/h (62 mph) with linear and controlled foot movement means a wait of a 2/3 seconds before the car accelerates, accompanied with an audible rise in revs

From a standstill - sometimes it will go on demand - but most of the time if I stomp on the gas pedal the car will think about it for up to 6 seconds (actually timed this) then dump power and take off. The power delivery isn't linear or predictable (despite what the dyno shows)

Things I've tried:

• Had the car checked by mechanics who could find nothing
• Checked by tuner
• There are no fault codes via ODBII
• Other intakes (Gruppe-M, STILLEN)
• VDC toggle
• D/M mode

The car is UPREV tuned with 220rwkw (300hp) at the wheels with an ARK Grip V2 exhaust, Fast Intentions HFC's and (currently) standard intakes.

Keen to hear any advice before I try weird ideas like throttle controllers and grounding kits

ZeN

I would check the switching value for both brake switch, you can do this with Nissan Datascan III and cheap ELM327 OBD2 bluetooth adapter on android phone. If both brake switch ok then check the timing when those thing happen.

Jhill

Two basic questions first before chasing things. Have you tried another 370z 7at to confirm yours is truly acting different? Also what has the service conditions for the trans been? I know they say lifetime fluid but that's usually just so the manufacture can advertise their low maintenance cost, if it's got some miles on it may consider flushing the atf, I think it was about 8 qts will get it really clean (2 drain and fills back to back).

jameZ_10

My 7at was very sluggish during shifts. My tuner fixed it while getting the uprev. He adjusted the pressure in the trans

__________________
stillen G3 * Invidia TP and CBE * uprev tune* 308 WHP

T-Rex57

Thanks Jhill, really great questions. I actually haven't tried another 7AT. I did come from a stock GM 4L60E auto car before, and I swear it shifted quicker.

I also haven't done the trans flush, and neither has it been done with any of my services at Nissan. I will definitely look into that

T-Rex57

Thanks Zen, I will try what you suggest

T-Rex57

Thanks Jamez. Tuner says nothing is wrong, but I haven't explicitly asked him to adjust trans pressure. I will do so

jameZ_10

I just figured that the crappy shifting was just something I'd have to live with. He just adjusted the line pressure and said " by the way I adjusted your line pressure so your trans should shift a lot better". It shifts super fast now. I love it

__________________
stillen G3 * Invidia TP and CBE * uprev tune* 308 WHP

T-Rex57

Hi ZeN, what constitutes the brake switches being OK? I did a quick run last night with the Datascan III app. Car seemed to be ok last night, that's rare though.

I've attached the DataScan CSV if anyone can tell me how to interpret it

NDSIII20161012_193456.csv.zip

ZeN

Theres 3 data PID that you can pull for brake switch. As long it switch from off to on or vice versa when you press or release the brake, ecu registererd it and that was not the reason your throttle were limited. You did said above that sometimes you had to wait up to 6 sec before it scream.

For the transmission, it could be valvebody going out.

SouthArk370Z

I'd try the following:
1) Clean MAFs (very easy job). If that doesn't improve things...
2) Clean the throttle bodies (not as easy as MAFs, but most weekend mechanics can handle it).

You might want to go back to a stock tune and see if problem still exists. If stock tune doesn't improve things, you need to start looking for bad parts, wiring, &c.

__________________
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Mankind has progressed past the need for war but we haven't evolved that far. - NachoMahma

T-Rex57

Thanks SouthArk. Took your advice and cleaned the MAF sensors. Really easy job as you said. They seemed pretty clean, maybe a very thin sheen of oil on them, probably from my old Gruppe-M intakes.

I cleaned them thoroughly with CRC MAF sensor cleaner. Haven't noticed a difference after a very short drive which I logged with Nissan Datascan 3 again. Will go for a longer drive tomorrow

I'll look into the throttle bodies next. I heard they are easy to damage so I might get a professional to do it

Should mention the slow response also existed on the stock tune

SG4247

Ive seen this issue a couple of times. It may be a stretch in your case....

The torque converter has an inadvertantly locked up stator. Usually the one way clutch (sprag) on the stator fails and causes the stator to not rotate. This causes the engine to seem extremely sluggish. Trans becomes slow and lazy. We spend weeks trying to fix what we think is an engine tune problem, and it turns out to be the torque converter.

Just a thought.

T-Rex57

Hmm, interesting. I do hear a small clunk moving into gear gear, almost like something is jamming or slipping.