First, I'll introduce myself. Been a reader of the site for a while. Just became a member not long ago. This is my first post. I have a 2k8 Black HHR SS. I love it, it is perfect for my lifestyle and what I need. Plus it doesn't look like every other vehicle on the road and when it is running correctly, it is a neck snapper. I live and work in the Indianapolis area. I decided to get an HHR SS when I saw another black SS a couple of years ago when I had my 2k8 Lancer GTS, that sounded like an angry sewing machine at WOT!. Now, about my issue...

This is a long story, but you'll need all the details so here it goes.

Last year around July (2010), I started getting intermittent loss of boost and power. Didn't matter how, where, or when I was driving. It would drop for short periods down to under 5lbs of boost and it continued getting worse as time went on. Up until then I had been running only the standard K&N filter element, in place of the paper one that looks like a 9 year old made as a school project, for close to 10 months give or take. Up until that time I hadn't been having any issues at all. It started getting so bad that it would start doing it just minutes into my commute to work and last for 5-15 minutes. It was intermittent, so I knew the dealership would have issues, and boy did they.

My car was still under warranty and I'd had it in for other issues like the TPMS not reading correctly which I'm sure many others can relate to. Anyway, dealership had the vehicle 6 times for upwards of close to a month total. They swapped the hot side piping, cold side piping, intercooler, and the MAF twice. The only time the vehicle ever ran for any length of time without the issue was after the MAF was replaced, which it ran for about a week before it happened again. The final time I had it in they replaced the K&N filter with the stock paper filter, the MAF, and the Intercooler (all at the same time ><). They went and claimed the filter was getting oil on the MAF and that was the cause (or so they said). I spoke with K&N and they offered to take the supposedly bad MAF and test it for oil accumulation, but the dealership had already disposed of it. I went ahead and left the K&N filter out to see if it ever did it again and it didn't. But again I couldn't be sure because multiple parts were swapped at the same time. I lost 2-3 MPG going back to the paper filter. I was getting 30-31 MPG on my commutes per tank and dropped to 27-28. I HATE those paper elements!

Anyway, the vehicle ran ok like that and didn't have another incident until it was time for an air filter change. I didn't go back to a K&N, but I wanted something that flowed more air and let the SS breathe again. I researched and researched air filter manufacturers and found S&B filters which is the ONLY ISO certified performance air filter manufacturer I could find. Part of that is testing at full CFM for oil contamination of MAF sensors. So I figured I would go with them. Problem was that K&N had about the only filter that would fit inside that tiny air box. So, I decided to take a chance and change out the box with the Dejon intake and a S&B filter on the end of that. Sure I no longer get cold air from the fender, but I plan on replacing the stock intercooler, which we all know has issues with heatsoak, with the Hahn Racecraft IC which should compensate for any increase in temps from the engine bay. Plus, it is winter here still.

So, I install the new intake and S&B filter about a month ago, and within 7 miles on my first drive I get a CEL for the MAF or VFA/VAF sensor. I don't have the code as the reader the autozone had had a damaged screen where the code appears... figures. I can't remember if the reader said VAF or VFA. Which you might help me with. As I understand it is another sensor in conjunction with the MAF up near the intake, but I didn't know if the VFA/VAF was the sensor from the IC to the intake manifold? The reason I ask is maybe that sensor is bad, I know the dealership didn't swap that sensor. They just stuck the crap filter back on and called it a day.

Now that you have the history. Here is what I deal with daily. I start the car up in the morning. I have CEL and full boost. I drive anywhere from 5-15 min and get loss of boost/power. At WOT I'll get 1-3 PSI, otherwise I'm running vacuum. If I stop and shut off the vehicle for a min, then restart. I'll get boost back for a short time again. I always have full power/boost after starting the car. I always have the CEL lit as well. My biggest question is why do I get the problem with an after-market filter or intake and filter, yet the worthless paper filter allows the car to run fine. Is the ECU not able to adjust for the increase in CFM being read by the MAF or VFA/VAF? Remember I had the same issue with the K&N pulling cool air from the fender, so before you start saying it is a hot air issue, think about that. Plus, I've had the issue during some of the coldest months of the year. It hasn't been higher than 60 yet.

I guess I'm asking for any suggestions or help in any way. The dealership doesn't know any more than I do at this point. They'll just put a paper filter back in and say deal with it. That to me is unacceptable, first the only place I could find a paper element was at the dealership and I don't want anything to do with them, part stores only sold the K&N. I am going to a different Autozone/Advanced this weekend to actually get a reader that will show the code. I just thought I could get some suggestions before the weekend. I don't have time for much at all during the week so, I can put any good ideas to use this weekend that any of you might have. Thanks for your help in advanced, it is appreciated! Hahn is also giving me some input but as some of you will probably ask, you want the code as they do. I'll post it here once I get it this weekend.

 

Here we go plain and simple. Our ECU is a tricky little ***** and doesnt like a lot of things. For every little mod you put in your car you NEED to tune. Sure some peoples cars run ok but in your case it doesnt. The MAF doesnt like what it sees cus its not what it was programmed to see and it will tell you to F*** off. So basically what i will say is put your stock filter in or find someone to tune you for the K&N but i doubt you wanna spend the money on a tune for only a filter

Mine did the same thing when i put my cold air intake on. Would be ok for a little then CEL with no boost. I would turn the car off then restat it and it would be ok. Trust me just stick with the OEM intake.

 

Well, I am planning on doing the programming, exhaust, piping, intercooler swap in the near future. From what you are saying, after I do my upgrades and have the system programmed, then I shouldn't have a problem?

 

Correct man. Get all of the stuff that youre planning on puttin on the car including the filter and then get tuned for it all at once. I mean you can do it in increments and such but its easier at once. And please use a reputable tuner. Keep the stock filter till then. I hope this helps man. Let me know if you need anything else

 

No worries, thanks for the assistance. I'll try and find time to put the stock box back in at least temporarily until I get my parts ordered.

 

I don't buy it. I put a K&N filter on about a year before I got the GMTU, and never threw a code. I've been running a BPV to atmosphere and IC pipes for about 6 months now, no codes. once the exhaust is on(in a week or so), I'll re-tune. but never once have I thrown a code, and it holds a steady 24PSI @ WOT! I really don't think its the filter, especially since the ECM, after the GMTU, has the Learn-Down function turned off.

No Boost lots of Vacumn means there is a serious pressure leak somewhere. If the car sounds like its winding out and your not going anywhere fast, then I would look really close at the IC for cracks in the plastic ends, you could have also blown out a T-map, check your fuses. Or it could be a busted BCV diaphram. Really though, your asking the wrong people. The engine is warrantied till 100K of 5 years have Chevy fix it. but again my guess, is bad pressure leak somewhere and my guess is cracked IC ends.

 

Some people have no problems and some have a bunch. A lot of cobalt guys have the same symptoms with their cars

Plus they swapped his IC and pipes like twice.

 

As I said in my original post. The dealership swapped the piping and IC and did full diag on the car. The problem with the dealership that yes, they may look at it and cover it again, but they will just want to put it back to stock since that makes the vehicle run normal. I think BartSS is on the right track with his answer considering he had the exact same issue when he installed his cold air intake.

 

I agree with FoolMoon..a lot more cars should have the same symptoms and they dont... not buying airflow as its turbo'd.....unless theres some sort of turbulance invoked..bad sensor position..semsor not clocked correctly in tube( something to look at). or a sensor thats not quite inside the parameters...even a loose harness with the CAI,,something..but not a filter....its allready been proven the K&N does very little...ambient temperatures will have a bigger effect then a that filter, even baro pressures.....maybe some of your cars are right on the edge with the stock tune,,which makes GM programming the problem...edge being just inside of workable parameters.But then it would show up in mountains and weather and such. This would be one for the engineers to poke around with,,,

 

Not the K&N Filter, although I can understand the dealer claiming it was with no other hints to go on. I run a K&N in the winter (too much fine dust around here to run it in the summer), and have not had a problem related to that with almost 60,000 miles. My only additional suggestion is to try using an MAF cleaner next time it happens and see if that actually makes a difference, I am betting not.