I start car up, idles totally normal, but hear a light whistling sound while idling and driving a little bit. The car drives fine, but no boost / maybe 2 lbs with stock turbo on 2008 Cobalt. What would cause this? No smoke, messages, or vibrations of any sort. Can someone lead me down a path or knowledge of what to look for so I can figure out what the problem is? Thank you in advance.

 

So you have no CELs but it wont boost? Something doesnt add up. I would first check for boost leaks via a boost leak tester not a visual inspection.

 

I get the P0299 code.

 

https://www.cobaltss.net/forums/how-...9/#post6120333

build that and test the system, the code is for boost lower than desired.

 

If it's not a boost leak it's likely a map sensor or the wiring. Had the same issue and replaced the lower sensor and adjusted the wiring route seamed to fix it.

 

It's possible I had a boost leak though as I replaced the lower charge pipe and intercooler at the same time and made sure it was not leaking as I went.

 

limp mode. i used to get that, had to pull my battery each time to fix it.