I recently bought a 09 Cobalt SS, so far I really like it as I have been wanting one for a while but there are a few problems. It has some aftermarket parts like a Mishimoto radiator, k&n intake, oil catch can, and an HKS BOV. I have a P0101 showing at this moment. This morning when I was looking for any possible leaks I noticed that the bolt for the rightmost spark plug was REALLY loose because the bolt was stripped. I had a P2188 code but after buying it a new bolt the code is no longer there, it also fixed a bit of the boost problem where before it was hardly giving me 5 PSI. After recharging the K&N intake today and cleaning the MAF and MAP sensor I took it out and it would give me around 10 PSI (I did not test it fully as I was only trying it out near my house) but after a few minutes of the car running it would the boost would go noticeably down fast to the point where it would barely reach 5 PSI. I would have to stop the car turn it off and turn it back on for the boost to go back to normal until a few minutes passed again and it would go back to hardly pushing any PSI. The old owner also told me that the car used to push around 300 HP but he decided to get it retuned back to normal again, maybe this has something to do with it? as for the flutter sound, I am not too sure what that could be, maybe the BOV??

 

I'm calling MAF sensor on this one. Pretty common. Was the code there before cleaning the MAF and the MAP? I ask, because the oil used on the K&N filter can get on the MAF and MAP sensor and cause issues. Did you clean one MAP or both? Where is your MAF located, is the MAF in the intake or is it in the cold side charge pipe? A BOV is not stock on the turbo Cobalt, the stock turbo uses a Bypass Valve (BPV) the gets a block off plate when a BOV is installed. Also from what I know about installing a BOV, to tune it properly the MAF should be relocated to the charge pipe.

The reason I say MAF, is that I had the exact same problem in my Turbo HHR. It would drive fine for while, and them it would pop p0101, it would still drive fine, but boost would be diminished to about 5 PSI. I could clean, the MAF and clear the code and it would be fine sometime for 10 minutes, sometimes a few days. Swapped the MAF with the one from my turbo Cobalt, and it solved the issue.

 

Yes, the code was there since I bought it, I just assumed it was not a big deal. I only cleaned one MAP, but mainly it was to see how dirty it was and it wasn't much so I decided to just leave the harder to get one the way it is. Do you recommend I completely remove the BOV? From what I have been reading on other threads the BOV is not recommended on the Cobalt and it is what I feel like is causing the flutter turbo sound. The MAF sensor is also located on the K&N intake and moving it to the charge pipe would require finding a place to put it on, which at this point I feel like it's easier to just take the BOV and replace it with the stock BPV.

 

Typically it's not a big deal. Usually something as simple as the MAF being bad. I missed this quote below.

If he had it retuned to stock then the BOV would be an issue. Like I said, a BOV most certainly will require a tune. The BPV is located on the turbo near the intake inlet. The stock BPV should have cream/tan colored plastic cover, held on by 3 small bolts, and a small vacuum hose coming off it it. Check that to see if that is installed. When you have time see if you can take few pictures. Try to get one of the intake side of the turbo, the BOV, and if you can, try to get a picture of the charge pipe that goes from the intercooler to the throttle body.

I feel like if it was BOV vs BPV issue there would be more then the MAF code. I'm still fairly certain your issue is a bad maf sensor, but pictures of your set up will help some, so we can kinda see whats going on. Also if you still have a way of contacting the previous owner, it woun't hurt to ask him about the tune, like who tuned it, what parts it was tuned for, and things.

 

The P0101 on the LNF almost 100% of the time is a boost leak. Which could be the BOV on a stock tune, the ecu isn't seeing the air it should and goes something is wrong with my maf

 

This is what I am working with, I could not get a good photo of the turbo, but after a quick glance, it has a cover over where the BPV should be meaning the original one is no longer there. The one with the number one is the BOV and I honestly just want to make this car stock again when it comes to that. But there are a few issues I have encountered. Like what is the original hose that gets connected to the second circle? I know that is not stock. I want to make that stock but where would I relocate that catch can tube? Also, I don't even understand why in the third photo there is (by the seems of it) a second solenoid? Sorry, I am full of questions I just don't quite understand what direction the old owner wanted to take the car in. I also can't contact the old owner as I don't have communication with him anymore.

 

Yeah, that's kind of what I am starting to feel like it is, I am going to replace the sensor soon just to eliminate the possibility that it is just a bad MAF. But if the CEL remains on I am going to have to do something about that dumb BOV.