DCOBALTSS

iTrader: (1)

So im getting this weird problem and it is very annoying.

When i have my ac/ or heating on let say im on neutral but with a certain speed 50km/hr my rpm keeps fluctuating between 1000 and 2500 rpm, without me pressing on gas pedal..

engine 2.4L
Is anyone here experiencing this issue..

Also i went to gm twice for this.
First time they say might be my throttle body, so they changed it..
Second time they said its because i beat the **** outa my car,

honestly i dont, on very very rare occasion.

Anyone could help with this..

Thanks

Sh0nuff

the car is idle hunting, get some maf cleaner and clean your maf, also check your air filter and make sure its good and clean, if not replace it.

outtamymind

could also be a glitch in the ECM as having the A/C on will cause a bit of an idle surge but shouldn't idle hunt. i would say as sh0nuff said clean the maf first and see if that helps, if it doesn't get a reflash done on the car from GM. can't be a straight reflash it has to be a new module reflash.

DCOBALTSS

iTrader: (1)

Ok so regarding the air filter it is clean. So ill take my car to gm soon before my warranty ends

Will ask them to do a check on the maf sensor clean it and do a new module reflash.

Any other ways to solve this problem will help..
I have a friend at dealership to he will help.

outtamymind

well the reason it has to be a new module flash is because if they reflash it with the same program it won't do anything as it doesn't see that there's a problem. i went through a week and 10 reflashes because after i cleaned my throttle my idle went all crazy and i flashed mine with the alternate program for blue injectors and back to mine and it fixed it instantly. could be a similar problem.

Sh0nuff

I had to have my 06ss flashed back when i was all stock due to idle hunting...
the reflash worked when cleaning the tb and maf didn't all it did was raise the idle rpm to about 1k.
in my opinion it has something to do with the throttle open % then open it a tiny bit more i guess, i dunno.

DCOBALTSS

iTrader: (1)

So ill tell them to do a new module flash.. hope they understand me.. Could you be clear and tell me exactly what i should tell them..
Thanks

outtamymind

It's a glitch in the ECM that for some reason will not relearn the idle even after doing a manual idle relearn

OP tell the dealership to do a new module flash to your module and I can vajra tee you it will work

insylem

Very common cobalt issue is dirty Throttle bodys....
Easy to do just clean the throttle body.
I had the same problem and that fixed it for me....
Here is a link

https://www.cobaltss.net/forums/2-0l...inally-116051/

outtamymind

He's a 2.4 the idle cure is completely different.

DCOBALTSS

iTrader: (1)

They already changed my throttle body to a new one..

I might be upgrading to a lsj tb we will see ...

outtamymind

changing the throttle bodies does nothing. with the 2.4's its an ecm issue that can only be fixed with reflashing the ecm via either writing a differen't tune and then loading the correct tune or doing a new module write to the ecm. trust me i spent a week trying to figure out the exact issue (mine was worse then yours but same symptoms) i tried 4 differen't known good throttle bodies and nothing changed, checked every last connection and voltages and even reflashed my ecm 10 times before i thought of flashing a differen't tune onto it and then back to mine.

G5GT2007

mine does that in the summer. if im in traffic on the highway or coming to a stop the rpms will jump up to about 1000 to 12000 and hold there for a few then will drop down to 500. only does it when im stopping

outtamymind

is your A/C on when it does this. what you describe is normal when the A/C is activated.

G5GT2007

yeah i think it is because its only done it in the summer its not doing it now.

insylem

oh ok then, I thought it would work the same for all cobalts.

outtamymind

no i wish it was, it seems the 2.4 ecm for whatever reason after being dirty for a prolonged period of time is unable to reset its idle. i spent a week trying to figure it out, (which is weird because it only happened after i cleaned my throttle body lol) i checked everything and swapped out everything. and like i said even flashed my car 10 times. until i had the idea of flashing the alternate tune and then immediately flashing my actual tune back on.

my theory why the reason why a regular flash doesn't work is because technically there isn't anything wrong with the system so the system doesn't actually overwrite anything but putting on an alternate tune and then back does an actual re-write allowing the idle to be corrected. i've seen it happen many times and i've seen so many tech's replace ECM's and while this does correct the issue it adds costs to everyone which can be saved with a simple reflash.