Not sure on why my down-pipe got screwed up but it is and its gotten worst. Not only does it sound like s#$# but i think its causing my 07 Cobalt SS/SC to idle to the point where it almost shuts off. RPMS just bounce up and down. Is my down-pipe really causing this horrible idle to happen?

 

How is the downpipe messed up? I know I had to replace spring bolts to hold on my flange and my evap valve was bad which made my idle do the exact same thing you mentioned.

Is there a certain time the idle spikes or is it all the time?

 

Yes, It would cause you to have a Rough Idle/Idle Searching, I just literally fixed an Exhaust leak that I had and the same thing was going on with my 07' SS s/c and it's Def a lot better now, Still Idle Searches every once in a while but not half as bad as it was. Get it fixed.

 

I'm still trying to figure this out myself.

When you turn the car on, do the RPMs start bouncing right away?

 

Check the sticky. Problem solved

 

Bad idle isn't just always the throttle body being dirty though.
It could be the MAF sensor being dirty as well and lots of other things.

Mainly my problem is that when I have the emissions fuse in in the fuse box, my car bounces up and down, eventually stalling.
When I pull the fuse, it idles perfectly fine. I don't know what it is, and I'm slowly trying to figure it out.

 

Emissions fuse? That sounds like its EVAP related then. Are you throwing any codes? You may need a new one of these: Cobalt Supercharged Evap Vent Solenoid Valve 12597567 - Crate Engine Depot

OP: An exhaust leak after the front o2 sensor is less likely to cause idle issues, but I would definitely fix/replace the downpipe ASAP.

 

Pyros, I might have to kiss you.

I was following this thread: https://www.cobaltss.net/forums/prob...-inside-93655/
I have the same codes:
P0030 HO2S Heater Control Circuit Sensor 1 ECM, PCM
P0036 HO2S Heater Control Circuit Sensor 2 ECM, PCM
P0102 Mass Air Flow (MAF) Sensor Circuit Low Frequency ECM, PCM
P0443 Evaporative Emission (EVAP) Purge Solenoid Control Circuit ECM, PCM

If you read through the thread, my emissions fuse was definitely blown. I wrapped my first o2 sensor with electrical tape, cleared the codes, started it up. RPMs would go bounce and stall the car.
Pulled the fuse, it's not blown.. So I ran out of ideas at that point.

I'm pretty sure I'm just throwing those codes, because the fuse is out but all of those things should be working.. besides that valve. I'm going to order that part though.

Any more suggestions, Pyros?

 

if the 02 sensor wire grounds out it popps the emmisions fuse.

 

i hate our downpipes!!! i've spent $300 trying to fix mine and so many hours and i still leaks... no idle issues though

 

It wasn't popped when I pulled it back out.
So, you think its the EVAP Purge Solenoid too?