AFR idel problem
 

Hello guys I have a gtm stage 2 sc and recently been facing problems with the AFR reading at idel, first of all the rpm Is shaky, and the afr sometimes reads between 17 and even goes up to 18 and at idel the car sometime cuts off kind like it will turn off then goes bk to normal how to explain it kinda like the belt losesns then tighten the car is hesitant and kind of laggy sometimes dont know if this is a tunning issue mechanical where should I start looking p.s dont know if this causes issues but im running a stage 2 gtm sc but the pully im using on it is the stage 1.5 pully please advise guys on where I should be looking:tiphat:

sounds like potentially a BPV problem? Wondering if the SC spinning at idle is not bypassing the extra air and causing the lean condition. Or it could be a vacuum leak post-MAF that is throwing the readings off (i.e. not accounting for all the air entering).

Had a similar issue, it was a tune problem.
Tuner needs to adjust the fuel/MAF readings I believe it is for idle. I would do a check of the system for leaks, but this is what caused my issue.

Thank you for the input guys can this potentially be dangerous on the engine during driving afr is good and stable only happens during idel so recordation to get the car mechanically checked for leaks etc then look at the tune

By the sounds of it you are having the same issue I had, tune check should fix it.
Also, are you running GTM can tune or a custom tune?

No I am running a custom tune thing is this guy tuned many fi 370z and it's starting to act up recently but wasn't happy with the drivability of the car ever since day one how can I explain it shifts in automatic and sometimes in manual isn't sharp the rpm is slow to react and sometimes jumpy also running a gym upgraded tranny, haven't been happy with drivability it's ruining the experience

the way i understand it is the gtm transmissions and valvebodies need to have the transmission table in the ecu tuned for them or they don't shift right/slip, you're tuner would need to talk to gtm and make sure the transmission is being told to do what it needs to properly. If you buy a $6000 transmission but don't get the tune adjusted for it you risk burning up the new transmission.

Come to think of it he was complaing about some slip on the dyno where can we get a hold of gtm with their messed up situation

If you didn't flash the tune that would cause it, another case of not following the instructions haha, I saw on myg37 there was a guy who just did the same thing, except he burned up one transmission, replaced it with another transmission, damaged that transmission, swapped in a new stock valvebody, then finally got around to tuning it after throwing out the gtm valvebody :facepalm:

Edit: if only he had put the gtm valve body in and then tuned it.

damm i hope that no damage has been done to the transmission but i dough it as car hasent been pushed or driven much the past year

Definitely make sure you have the right tune on there!

The idle issue is very possibly a bad bypass valve. Any hiss or whistle under the hood?

by bad bypass do you mean the pvc bypass is connected wrong or filter is dirty needs cleaning, there is a whistle but i assume its the sound of the sc unit also at times in idle the its as if the car stalls, stops for a sec as ifi twill turn off and then goes back to normal, at this time as well the afr goes to 17 18 and sometimes ---- comes on no reading

no he means the blow off valve looking thing could be open when it isn't supposed to be, on the supercharged cars i believe the norm is that it is supposed to be open under idle though to allow the excess air to recirculate. the idle is most likely an issue with the maf curve, when they tuned your car for WOT they mostlikely adjusted the k value to bring the ecu closer to the afr targets and never went back in and tweaked the maf values below 2 volts to get the idle back.

EDIT: if it was slipping already don't drive it and get the transmission tables tuned ASAP!!

I would think tuning too, but he said the problem has just recently developed. I would think a tuning problem would have been apparent from the start.

oh i thought he was recently retuned, assuming the tune was good check for air leaks between the maf sensors and the throttles. anything before the maf wouldn't cause it, unless it was something really wrong like the bypass valve stuck closed at idle.

whats your AFR at cruise speeds and at WOT? Are they dead on?

thank you to everyone who chimed in with various things to look out for, after opening this thread i decided to pull the trigger and ship the car to a tuner to take a look at it, and the finding he found were shocking, first of all the AFR were crazy and car cutting off at idel was due to the fuel trims in the previous tune to be messed up also noted slight knocking at normal driving which has been addressed and the drivability issues as well ( slow response, lazy hesitant shifting, jumpy rpm) everything that can go wrong with the car basically, also changed my pully to 92mm from 96mm on a stage 2 sc so should be more fun, and got a uprev back fire map, iv invested so much on this build and used only the best of the best parts and i was pissed that the outcome was crap basically iv hated to drive the car for the past year and a half leading to abandoning it and being parked for months not being driven, i hope this new tune rekindles my love for my z and get to enjoy is as much as before if not more iv had a sc on my car for the past year and havent even enjoyed or felt it and what kills me is that i read many posts of guys here with similar setup if not less than mine and they are raving about how the cars preform and i havent even felt any joy or even power, wish me luck guys that tune goes well and ill keep you all posted for sure.

Good luck and hope everything goes well! :tup:

Numbes are in guys 457 hp 334 tq on 8 psi on mustang dyno extreme hot humid weather and bad fuel overall pleased how much will this convert to on dyno jet?

Nice -- congrats and glad you got the problems sorted out :tup:

Any idea what a stock Z puts down on their dyno? It's hard to compare and contrast between mustang and dynojet...

If I know what a stock Z put down on their dyno, I can give you a good ball park estimate.

ill have to ask my tuner that and get back to you on it, the thing is i did not do a before dyno with my old tune as my tuner was afraid to push the car at first cuz he detected knock and fuel trim problems when he initially checked the car

Understood.

I can still give a pretty reasonable estimate if I know what a typical stock Z puts down on their dyno -- I have data on around a dozen VQ37HR's on dynojets in both 4th and 5th gear, so I can calculate the approximate % difference between A and B and give you a close estimate.