EJVYFZ

iTrader: (3)

Just got my car retuned by mike norris. he is an absolute great guy, and i was extremely happy with the experience. the car has ran great since his tune, but i do have one question about something that has came up. when i have the ac on max turned up all the way, and as cold as it will go, the car wont start without some throttle. and also, when i was out messing around a back road in the middle of nowhere, I tried messing around with launching the car. again the ac was on, and after launching the car, i saw someone coming down the road on a moped. so i got on the brakes pretty hard so i wouldnt scare them. when i got on the brakes hard, the rpms dropped really low and the car almost stalled out. so this got my attention, and after the moped passed and i was sure the road was cleared again, i did the same thing. i launched the car hard, and then got on the brakes a few seconds later, and the car died. now, is this normal? it doesnt seem to be a problem with the ac off. i dont remember having this problem before the retune. the car runs waaayyy better in every other way, im just wondering if this is normal. also, the previous tuner had tuned out my front 02s.. Mike said something about this affecting warm up times and idle. could this be a factor? i plan on calling mike and talking to him about this tomorrow, but thought i post this so i could be more educated on the subject. or if its normal, ill make sure i dont waste his time. haha thanks guys!

Ice78Transam

iTrader: (1)

No, it's not normal. That's likely a vacuum issue when braking causes the engine to stumble.

EJVYFZ

iTrader: (3)

any ideas on where to start looking?

flintwrench69

iTrader: (11)

Youre idle needs to be increased some more, by the tuner. Mine does this too & its been happenning since I had the tune done. It does this only with the A/C on.

FireChickenws6

iTrader: (1)

Sounds like the ECM doesn't know to bump the idle to account for the increased load with the A/C on. Your tuner should be able to take care of it.

I would say I have seen nasty throttle bodies do this as well but I am going to assume yours is clean.

Z28_LT1

iTrader: (2)

Also, I think you mean he tuned out the rear O2 sensors. The front ones are the important ones...

2slow2flurry-ous

iTrader: (13)

Ditto..

BigBirdLS1

Hey guys I see several of you are having the exact same problem I have been having. I had my cam installed and dyno tuned and the dying issue came up. I called my tuner and he sugguested that turn the throttle blade screw in a little to bring in more air at idle. I adjusted the screw and it seemed to help sitting in my driveway but I have yet to drive it. I hope this will help you guys.

EJVYFZ

iTrader: (3)

^^what exactly do the front O2's do? I know mike said that he couldnt understand why the previous tuner had tuned them out. but i thought it was common to tune out rear 02 sensors when installing LTs? Mike said multiple times that he had no idea why it was done like that, and that it was kinda like having a carb on the car? does that sound right? I may have heard wrong, haha.

EJVYFZ

iTrader: (3)

thanks for the advice man. but my car sits at idle great, at right about 950 rpm. its really just a problem during heavy acceleration followed by hard breaking while the ac is on.

BigBirdLS1

Your having the exact problem I have. If I am driving and all of a sudden stab in the clutch to slow down it dies almost instantly with the a/c on if I have the a/c off it will never die.

twitchtwice

iTrader: (12)

the front o2's is where the computer senses how the afr is. without those the car wont run right. the rear o2's are there to check and see if the factory cats are doing their job, but almost everyone deletes them because with all aftermarket exhausts there is no need for them.

USArmyZ28

iTrader: (3)

I had the same problem, you have to get the air flow at idle tuned again.

flintwrench69

iTrader: (11)

The front O2s are used for fuel control & are very important. They sense the amount of oxygen or lack of oxygen in the exhaust system & the PCM uses this to adjust fuel injection time. The rear O2s are only used for catalyst monitoring, emissions only. Deleting them will have no effect on fuel control & are commonly deleted after headers, cat delete, etc.

blk/slvr02ss

iTrader: (21)

Seems to me like u need the IAC adjusted but that is not a big problem if its only doing it w/ the A/C on and a cam could also affect it w/ the A/C on.Mike will let u know.

EJVYFZ

iTrader: (3)

ahh ok guys. thanks for all the advice. i know mike will set me straight! cant speak highly enough of him. gave him a call today and left a message, i know he is in florida this week but im sure ill hear from him early next week. ill let you all know what i find out!

PitchblackC3

iTrader: (3)

Maybe the previous tuner had it so it couldn't go into closed loop, effectively tuning the front O2s out.
Which is a pretty crappy way to tune BTW.

EJVYFZ

iTrader: (3)

^^ bingo.. i remember mike saying that.

EJVYFZ

iTrader: (3)

what would it take to bring the O2s back? would it just be a matter of tuning them back in? mike said something about how because they were tuned out it would affect my warm up time, but he said if it didnt bother me then he wouldnt ask me to pay the money for no reason.. so do i need to buy new O2's

flintwrench69

iTrader: (11)

I am not gonna claim to be a genius at tuning but I am starting to learn how. When tuning a car youre supposed to disable the PCM from going into closed loop. This does not disable the the front O2s though. Then after youre done tuning you re-enable the closed loop function. This is done so the PCM isnt adjusting fuel control while youre trying to make corrections during tuning. I highly doubt your tuner did anything to disable the front O2s or forgot to go back in & re-enable closed loop function if youre tuner has the good reputation I think he does. IMO getting the idle adjusted right can be time consuming, & seems to be the main thing that needs to be gone over again. I had mine tuned & had to take it back because it stalled a lot. Now it mainly stalls with the A/C on. Its waaay better than before though, I will address it when I put my heads on soon.