So I am at 65K and about a month ago after showing a Challenger owner what we got in our little Cobalts it all went downhill. The problem is P0299 under boost (Encountered it few times). Here are the symptoms. After the car is at operating temperature first WOT is ok boost about 22 PSI and hold. Driving little more WOT boost only to about 15 PSI and hold. Third WOT no boost 0 PSI. No CEL most of the time if I recycle the ignition I will go back to 22, 15 and 0 PSI. I did a boost leak test was leaking little at the diverter vale and a catch can removed the catch can and put a new gasket on the diverter valve all good now. The signs also lead me to believe it’s not a boost leak problem but something electrical any thoughts>? Also I did notice a slightly different blow off sound like to best describe it is like sooner more pronounced. Any help is greatly appreciated.

 

Does it take awhile to boost to 22 psi?

 

Now that you've fixed two boost leaks test it again.

What tune are you on?

 

when it get to 22 it is quick like it always was ad it hold it too. i did notice that when the issue is present it will take a while to get to 15psi. also when if it gets to boost to 22 it will be holding for a second or two and than just suddenly drop to 0 and stay at 0 until I recycle the key. i did boost leak test after and it looks like is fine no leaks. also i have gm stage one. thanks.

 

anyone? or am I the first one to experience this?

 

I had the exact same issues turned out to be a boost leak in my intercooler and tons of play in my turbo.

 

Check your MAP sensor wiring, make sure it's not chaffing or snagged on anything. Also check to see if map sensor is clean.

 

Finally got around to the car 2 weeks ago. I checked everything and followed the suggestions. I removed the MAP sensor and cleaned the tip. No results. Fond some people on this site who had similar issues they replaced the vacuum switch solenoid. So replaced the solenoid and for about 2 weeks now car runs like new no issues full boost. Thanks for help

 

Do you have the PN for the vacuum switch solenoid?

I am having a P0299 pop up a few times now and don't see anything else mechanically wrong. Could be a boost leak, but I don't get the rich code to go with it.

Like you after it throw the code an goes into limp mode, I just turn off/restart, and it will boost fine for a few gears or a little while, then do it again. But until the code is thrown it seems fine and boost is perfect.

 

TU312 Vacuum Switch Solenoid 2008 10 Sky Solstice Cobalt HHR Regal SS 2 0 Turbo | eBay


I got mine off eBay someone else posted the link to this part. So far shes running like a champ no more p0299. I believe that for me the valve was stuck open because one time i took the vacuum line off of the diverter valve and it was under vacuum. i read your other post maybe your is starting to fail. for 20$ its a cheap and easy fix. Good Luck.

 

just remove the stupid solenoid and delete the codes, future issues solved

 

Thanks. I just ordered one up. Too cheap not to just replace it.

Where is it located on the engine approximately?

 

1. Quote:

   Originally Posted by tomj77

   just remove the stupid solenoid and delete the codes, future issues solved

I might do this possibly. It seems that this is really unnecessary possibly. It is just a solenoid so the PCM can control the BPV, is that correct? If so, I guess the BPV will function and react the same if the solenoid is gone.

I have seen the vacuum tank delete thread before, but not sure if I have seen this one. Can you link me to a thread on it if there is one?

 

there is not thread on this one, some of us just did it because we have had the solenoid go bad a few times and cause issues. The solenoid is there for a few reasons. its there to protect against overboost, the ecu can open it when it detects overboost, which on a tuned car is usually tuned out anyway. and the second function is with the solenoid the bpv will never see vacuum at idle, just pressure, to hold it closed so it doesn't leak, which I don't think matters cause the air never leaves the system anyway. other than that it works the same way, actually will be a little faster without the solenoid.

 

Thank you.