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Discussion Starter · #1 ·
I just had a quick question for all of you SS owners out there. So far I love my cobalt and everything about it. However, I have noticed a few things... and I wanted to see if anyone else noticed these as well, or if I should get tot he dealership to have them lookat/fix these problems.

First, When I start my car up and just let her idle for a min or two... I notice a slight rattle coming from underneath, I'm not sure but it sounds like the muffler rattling on something. Anyone else notice this?? When I rev it up, the sound basically goes away, but when its idling or lightly getting on it, I notice it once in a while...

Second, I was reading in the owners manual, and it was talking about the boost guage reading approximately 0 when the car is turned on and idling. My guage is pulling 10-15 vac when its idling. Is this a problem, because I don't know a whole heck of a lot about cars, especially ones that are designed for some performance.

Any info would be appreciated.
 

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Well, My 'balt ss does not have the Rattling exhaust problem, could be a loose clamp, That's what happened to my 2000 Mitsu, i thought it was a hole, but just a loose clamp. Anyways, My boost reads about 10 vac while idling as well. Not sure if both are wrong or what but hope this helps.
 

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Discussion Starter · #3 ·
I'll have to get under the car and take a look see. Thanks for the reply.
 

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Your car should not be pulling 10-15 vac when its idling. Bring it to the dealer I would.. I have a SS and mine does not do that..
 

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it should be at 0 when it's idling? i might be wrong here, but the only time a car would read 0 is if it was a naturally aspirated car at WOT, or a sc car like ours with the gate open, but no boost yet.


0 on a vacuum guage means that it is at Absolute Pressure, that means there is 100% vacuum.


not sure why your car is running at 0 psi/kpa (absolute pressure), because if it is, you might want to take YOUR car into get looked at BizoCG
 

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Hey bro that rattling noise, not sure what that is. I don't hear it on mine. But on the boost, mine reads about 10 or so. I think the only time that it reads 0psi is when the engine is shut off. or when you are driving and giving it enough fuel to read 0 psi on the road,there is always going to be a some vacum reguardless. So i think you are G.T.G. ( good to go). But it's good to get a second opinion on it. If anyone is out there they think i might be wrong please let me know. thanks. :)
 

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Red'BaltSS, mine does the same thing.. Especially the rattle when it first starts up. I didn't notice mine until I was showing some friends it, and I had the door and hood open. I can't hear it with the doors closed, and the windows up.
Those of you that say you can't hear it, might want to start your car up with the door open or the windows down just to be sure ;)
Also it only seems to do it when the engine is cold.
 

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Well when it is idling mine reads 10-15 but see the thing is when the neddle is there on the tack I think the tack should read a - but when the tack go's above the 0 I think the tack should read a +.. Any thoughts on that. I just think the tack should have a - + on the tack. Thoughts just my thoughts on it..
 

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What i get from having the whole boost and vacum thing explained to me is that it relates to the power it is taking in. When the car is below zero it is running on vacum which means you are getting great gas mileage and absolutley no boost. Once it crosses over the zero the car is running on boost which is producing the power for the engine which is great for racing and horsepower but poor on gas mileage. So there is nothing wrong with the car running in vacum when you first start it because you do not want the SC running at idle and vreating power for no reason.
 

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At idle is when there is the most amount of vaccum. My Supercharged Cavy runs like 20vac at idle.
 

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all cars HAVE vac at idle

that's weird that the cobalt ss runs at 10 vac. my redline runs at 20 vac at idle.

the rattling is your cat.
 

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SLCFAST4 said:
All cars have vacuum at idle... You guys can't be serious!! I have entered Darwins waiting room!!!! :eek:
fine let me rephrase this: ALL cars i've owned and my buddies have owned have vacuum.
 

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Red'BaltSS said:
I just had a quick question for all of you SS owners out there. So far I love my cobalt and everything about it. However, I have noticed a few things... and I wanted to see if anyone else noticed these as well, or if I should get tot he dealership to have them lookat/fix these problems.

First, When I start my car up and just let her idle for a min or two... I notice a slight rattle coming from underneath, I'm not sure but it sounds like the muffler rattling on something. Anyone else notice this?? When I rev it up, the sound basically goes away, but when its idling or lightly getting on it, I notice it once in a while...

Second, I was reading in the owners manual, and it was talking about the boost guage reading approximately 0 when the car is turned on and idling. My guage is pulling 10-15 vac when its idling. Is this a problem, because I don't know a whole heck of a lot about cars, especially ones that are designed for some performance.

Any info would be appreciated.
First of all I just got my SS a couple days ago and my exhaust does the same thing. But it doesnt do it when im driving...i dunno, it might be normal. But in the owners manual it says the boost will read 0 when the key in on the ACC position....because there is no vac or boost going to the SC. When the car is idling it will always have Vac.... turbo cars do the same thing...... My car gets 20 vac at idle. Its normal, because the SC is not producing boost until the gas is pressed then it will go up, but it doesn't neccesarilly pass 0 when your driving either, depend on how much gas you give it. hope this helps.
 

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Red'BaltSS said:
I just had a quick question for all of you SS owners out there. So far I love my cobalt and everything about it. However, I have noticed a few things... and I wanted to see if anyone else noticed these as well, or if I should get tot he dealership to have them lookat/fix these problems.

First, When I start my car up and just let her idle for a min or two... I notice a slight rattle coming from underneath, I'm not sure but it sounds like the muffler rattling on something. Anyone else notice this?? When I rev it up, the sound basically goes away, but when its idling or lightly getting on it, I notice it once in a while...

Second, I was reading in the owners manual, and it was talking about the boost guage reading approximately 0 when the car is turned on and idling. My guage is pulling 10-15 vac when its idling. Is this a problem, because I don't know a whole heck of a lot about cars, especially ones that are designed for some performance.

Any info would be appreciated.

Hi everyone,been watching the posts for a few months. Picked up my SS two weeks ago, I love except for the sound of the exaust system. Took it to the dealer last monday and the said it had a broken baffle in the muffler. The sound was there when I first picked it up (sounded like a loose heat sheild).
The sound was there on start up and in first and second gear, went away once revs went over 3K. It has got worse and is always there. If your SS is doing this to, get it in to the dealer. A guy on another forum said that this was a common problem and takes 3 weeks for the exaust to come in. Hope this helps those of you with exaust sounds. Answer to second concern,vac is ok at idle, guage should only read 0 when key first turned to ACC (calibration)
and when accelerating on your way to "boost" .
 

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selfinfliction said:
it should be at 0 when it's idling? i might be wrong here, but the only time a car would read 0 is if it was a naturally aspirated car at WOT, or a sc car like ours with the gate open, but no boost yet.


0 on a vacuum guage means that it is at Absolute Pressure, that means there is 100% vacuum.


not sure why your car is running at 0 psi/kpa (absolute pressure), because if it is, you might want to take YOUR car into get looked at BizoCG
The bypass valve IS open at idle. Here's a link to a thread that describes when the bypass is open.
http://www.cobaltss.com/forums/showthread.php?p=11358#post11358
HTH
WopOnTour
 
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