Car is a '07 SS/SC w/ Stage 2 and an airbox mod (AEM Dryflow) . I took a good friend and my wife for a ride yesterday WOT up through the gears to 120 a couple times and then came back into town and filled up...Car seemed sluggish after I filled up but I didn't think nothing of it. Well I went to work this morning and the car still felt sluggish so I looked at the boost gauge and no matter what I couldn't get it to boost over 2.5 lbs no matter what gear or RPM. Still drives fine just no power and no boost, can even still kinda hear the SC whine, just no go...What gives ??? Anybody ever experience this ???

 

i havent had it happen...but maybe your bypass valve is stuck? just a thought!

 

How can I check it...

 

you could always try the bypass mod to see if it is the bypass loop or not...

https://www.cobaltss.net/forums/how-guide-43/how-boost-bypass-mod-11994/

but i wouldnt run it like that for a long time if it is, i would take it to the dealer!

 

You should take it to the dealership immediately. It may not be a big deal, but then again there is a chance that something could cause major damage. I wouldn't even try to mess with the bypass valve either, just let them fix it.

Do you feel a misfire or any change in how it cruises, or is the problem only when you go WOT?

 

dont listen to the guy suggesting the bypass mod. BAD IDEA. this causes boost to build even when the throttle is closed, during low lift operation...BAD IDEA!

check the hoses going to the bypass actuator and make sure that none of them are missing/disconnected. then check for any cracking. if there are no cracks, no missing hoses, then look for leaks.

check your boost gauge line to see if its installed properly.

if none of that works out...dealership.

 

...i was just suggesting the bypass mod as a way of diagnosing the problem, not as a fix! But i would just go to the dealer on this one...thats what the warranty is for!

 

^i know. not trying to single you out. just saying how detrimental the boost bypass mod really is, in the long run. its there to prevent overboosting as well.

 

i gotcha. This deff. has to a problem with the recirculation system...if it was the gauge the car wouldnt be sluggish. And hope to god the PCM isnt causing the bypass actuator to stick...that would be a big issue.

 

^in this case it would be stuck in the open position. its made to fail in the open position, so if you lose any lines, excess pressure does not build up, blowing the head gasket.

 

thats true..and its exactly why they build it that way. im just saying that nobody wants a pcm problem, no matter if its detrimental to their engine or not. But chances are that if its stuck for some reason it will be a line, or just a bad valve...a relatively easy fix!

 

*places $5 bet* on "check your boost gauge line to see if its installed properly. "


n/m...just remembered the stock boost gauge in the Cobalt is electrical. still, check all the boost/vaccum lines going to the bypass from the manifold...

 

did you fill up with 87 octane accidentally?

 

Just pulled the codes and got a P0171 and P0300...I'm trying to see if it will reset by disconnecting the batt...

 

remove the belt and see if the blower spins freely would be my first step, then look for leaks in the induction system. Check the boost bypass, make sure it's not stuck the lines are all solid, stuff like that. If you have a friend rev the engine in neutral you should see the bypass actuate.

 

Nope always 93 for all my vehicles...even my weedeater doesn't get 87...

 

P0171 Fuel Trim System Lean -PCM (un-metered air between MAF and TB)
P0300 Engine Misfire Detected -PCM (bad!)

 

Also one line is a little dryrotted but I took it off and tried to check for leaks but I did'nt find one...

 

with those codes it is reallly sounding like a leak in your vacuum system is causing you to get more air than fuel...

 

also, check the line that goes from your PCV to the intake, make sure that line is connected.

 

Well, i always say, look at what you did before the problem happened. You sayed you filled up right before going home. Sometimes i find myself reaching for the wrong pump because different gas stations put them in different places. the station could have actually fucked up and filled the wrong octane in the actual pump (highly unlikely though). I'd say cyphon the tank if you can and fill up from another gas station with 93 octane, maybe put in some octane booster.

Edit: I get the p0171 from my airbox mod, its nothing to worry about, the other code is definitely showing you whats wrong. Too low an octane will cause your misfire.

 

From what I can tell all hoses are connected...I pulled the suspected dry rotted hose off and pressure tested by old school method underwater and no leaks, PCV hose is connected. Car starts fine...After connecting the battery and going for a drive it is still the same but the codes are cleared...

There is a sensor that seems like a MAP sensor that is just under the supercharger but mounted on a braket coming off the block. It looks just like a MAP sensor but it is out in the open w/ nothing conected to the underside but it has wires going to it. Is there supposed to be a hose or something connected to the bottom of it or something ??? Anyone know what it is???

Check post #16...

 

i saw post #16, i'm just saying, root cause. I always fill up on premium as well, but 87 octane will cause misfire or and sluggishness at WOT. I'd say you have nothing to lose if you can't find the problem.

 

Have you watched the actuation of the bypass vavle yet? It'll even change position when the car is off to when you turn it on if you don't have anyone to rev it for you.

 

Yep it moves, it's slightly open while at idle and closes (I guess closes) while reving it and when the engine is off...