The original post makes it sound like the problem is only with the K&N. I didn't see where he had put the stock intake back on and still had fuel trim issues.

 

I know, Im guilty of reading the first post and responding immediately in alot of posts too. What I wrote is the short story up to date.

He did find a leak in the upper charge pipe. Bought a new upper CP and replaced it but still has something causing the high LTFT. Also he replaced the blue o-rings with black ones on the 3 bar MAP sensors.

 

I still have all the lines running from my bypass solenoid on top of the manifold. Would one be removed if there was a tank delete? I assume I can also look for the tank underneath and to the passenger side of the IM?

 

just to put this out there i ordered a replacement air filter for my k&n intake and the k&n logo on the backside was not in the same place as the other filters i previously had. "Made in the USA" was at the 12 O'Clock position. The front K&N logo was oriented the same as the others tho...upside down. Just something to look out for.

 

Was the issue present before installing the K&N intake the first time?

 

If you want to bypass the tank just to see if anything changes, all you have to do is disconnect the line on the solenoid that's facing the front of the car, disconnect the line on the intake manifold, then run a line from the solenoid directly to the manifold.

 

The LTFTs were indeed +15 BEFORE installing the K&N intake. I had not known that it was a problem at the time until I started reading more into the forums as well as the people posting on this thread. My theory is that with the addition of more air entering the system (from the intake) along with a possible vacuum leak, the car cannot safely compensate enough through fuel trims to perform normally with the intake installed.

 

If that's the case, I think you have more serious problems than a vacuum leak. If it's still under warranty, you might want to take it to a dealer. I've had bad luck with dealers in my area, so I hesitate to recommend that, but it sounds like it would be worth the hassle in your case. Especially since your car has only been on GM tunes with stock parts (I assume).

 

Correct. However the dealers around me are ridiculous and have never worked on these cars. One tried to tell me the charge pipe and even the turbo weren't covered under power train warranty.

There is a great dealer 80 miles from me...

What "more serious" problems are you thinking of?

 

UPDATE:

Decided to bypass the vacuum tank after spraying it down really good and not seeing any bubbles (used my air compressor to pressurize it). Took it on a drive and fuel trims did not move however right after a hard 1st to second shift I heard a loud blow off valve sound (I did not "no lift ****"). I thought I had blew the hose off but it was fine. I figure its because the tank was disconnected (I had read that on here at one point).

Removed the bumper.



Sprayed the entire intercooler and all fittings (both sides of IC, the couplers, the plastic rings, etc) and did not have any leaks. I put almost an entire spray bottle on the thing trying to find something.



Before we had the bumper back on I noticed that the brake booster line looked a little odd and I decided "what the heck, why not" and liberally sprayed it. LOTS of bubbles from between the manifold and the plastic fitting. See picture:



I tightened the fitting and ran the boost leak test again. No bubbles. I was very excited that I had found another leak. After getting the bumper put back on I took a drive to town (15 minutes one way or ~8miles one way) and the LTFT hovered around 3 until it AGAIN rose to an average of 15%. The maximum it hit during the run was 24% at idle and parked.

I'm at my wits end. I have found and fixed TWO quite large leaks in the system and the fuel trims have not changed one bit. The rest of the piping was also leak free.

I think I will remove that fitting to check for cracks and maybe use some RTV sealant. If I can't figure it out soon I will be taking it to the dealer and driving a different car while they figure it out.

I also was wondering if the valves gunking up could have something to do with it, but it does not follow that more gunked valves would lead to more fuel being added...

 

nah, the valves gunking wouldnt cause at LTFT like that. Im glad you found another leak but it sucks that that wasnt the answer either. You may want to go over every vac line, at each connection point. Diaphgram on the BPV could be another point. The vacuum deleltion had mixed reviews. Let us know how that goes. The dealer might attack you for it.

It suppose to provide the charged air with a place to go after the throttle closes to reduce the "chance" of compressor surge or whatever its called when the turbo is forced backwards in rotation.

P.S. - ZZP pipe looks good


24 LTFT should cause a CEL. no CELs? Im thinking the dealer might tell you nothings wrong with the car since there's no CEL. Good luck! I hope they arent stupid and listen to your story of what you've gone through, that you've found two leaks in the system but the high Long term fuel trims still have not been resolved.

 

Okay, I think you've done alot of work to try and find this leak. Im going to go down to the basics here. The device your using to check on the LTFTs, Torque? Thats the cell phone bluetooth application? Has anyone proven that it accurately reads the LTFTs correctly? The reason why im bringing that up is that you did didnt throw a code when you hit +24% LTFT. It has me curious. I think you should ask about any local tuners in the washington area that can datalog you to help you solve an issue with Fuel Trims before going to the dealership. I mean what you've done so far to solve this, the dealer wouldnt have even tried.

Theres a North Pacific Section in the local area section North Pacific - Cobalt SS Network

Ask if anyone has HPtuners in your area and is willing to check your car out?

Im pretty much out of ideas myself except for the BPV but I dont think that has an issue cause you would have no boost. Only other thing to do would be to just tune the car since you've not found any leaks (besides the ones you fixed).

 

I returned the vacuum tank to stock configuration.

Added rtv sealant to the brake vacuum line fitting.

It seems too odd that two decent leaks had zero effect on the trims. I was honestly wondering if torque was being accurate. Because yes, there were no check engine lights.

But that would not explain why my intake would cause the car to run like crap.

I will ask about tuners. Thanks for all your help so far!

 

New problems.

I was leaving from work the other day, car was still warming up, and I was at the stop about to turn onto th road. I turned onto the road and while letting the clutch out in first and the car started bucking pretty good. I was able to complete first gear though as it stopped by 3000rpm. It was not due to not enough throttle on my end.

Now that I think of it it has done this multiple times in the past but I had thought it was me getting used to the clutch in this car.

Idk. Looks like trifecta is the only tuning source in my area as well. I think I'll be writing up a summary, printing it and taking it with the car to the dealer.

 

Reinstalled the k&n filter and intake today to see if it would perform differently now that I have fixed the boost/vacuum leaks. The car idled much better than it did the first time, however, loud grinding/popping noise are coming from the turbo or intake. I took a video that you can clearly hear what I am talking about. Please excuse my stupid loud voice, my neighbor was over and he is hard of hearing.


New link (the first one was all corrupted.

http://s183.photobucket.com/user/CA_...81237.mp4.html


Lets see if that works. I used the Photobucket direct link as well as the IMG code.

 

That's pretty strange. When the car was shutoff it sounded like the bypass valve was fluttering. That happened to me when I switched the lines on the vacuum tank. Have you double checked the line routing and the BPV?

 

I haven't checked the bypass valve. I did check the bypass hose lines and pressure tested the tank. Could the solenoid where the lines are going in be bad as well? The lines are visible in one of the pictures above. They look normal to me. Just to make it clear, this only happens when the k&n is installed.

I have been hearing the bypass valve on fast acceleration shifts which I've never heard before.

 

definately flutter. Lets see if I can post a similar video



In my case, it was a tuning issue. I wanted a combination of Trifecta and HPtuners. The Trifecta file was corrupt and basically the waste gate wouldnt close all the way ~2psi at the most was readable so the car was running at somewhere just barely north of 0 psi/vac and the bpv would make that flutter noise.

The only other way to make that flutter noise is if the bpv did not open and release the pressure. There a few reasons that may occur. Vac line routing is blocked, or there is a leak causing the BPV not to open under the correct vacuum/boost.

There was another thing cobalt ss owners were doing back in the day to try and artificially creat more boost by blocking one of the vac lines. It was called the "Pill mod". They would put a tip for a sauder gun or welder in the vac line to restrict the flow just a bit and somehow that created more boost... I dont know the specifics, I stayed away from the snake oil / witch craft mods.

I think your next objective should be to carefully take the BPV off. Its held on by 3 hex bolts, I think they are 10 or 11 mm. Dont remove the vacuum line until the BPV is unbolted off and you can hold the diaphragm and spring in place. My experience is they shoot off once you take the vac line off lol.

Inspect the rubber diaphragm for tears. The previous owner definately did some mods here and there and they may be hidden things like that "Pill Mod". I can see he replaced the gauge cluster.

P.S. - Guaranteed your car is making the same noises under the factory airbox as well. You just cant here it because of the black plastic baffling in the intake tube. The K&N intake is like a megaphone for the turbo. Next time you have the intake off, put your finger on the bolt holding the compressor on in the turbo housing and see if you can wiggle it easily (dont force it to move if it doesnt want to move). If it wiggles more than 2-3mm in the up and down or left and right direction, the turbo may need alittle work :/

The turbo sounds like its surging on start up... Its possible since the start up builds alittle boost. Do you get surge when you accelerate?

 

Here I found alittle something about it. maybe this info wil lhelp you find a "pill mod" on your car :/

 

Grinding noise is actually the sound of the air vacuuming through the intake tube. Its very loud and can sound bad. The only thing troubling in the video is the stumbling under idle and the slight turbo flutter.

 

When I unhooked the bypass tank lines to do a pressure test on them I could only add air through one of the lines. The other acted as though it had a check valve in it. I didn't say anything as I thought that made sense. The line going to the manifold was the one I could not blow into.

I will do all of these checks and get back with you. Thanks SO much for giving me something else to hunt for. I was about ready to give up and take it to the dealer.

I'm not sure what you mean by surging though. Surge in rpm or boost? Or do you mean compressor surge/ fluttering?

 

holy crap just watched that video

That's way too much flutter when you turn it off.

The louder sound is hard to tell if it's air woosh or a banging sound.


Sure sounds like turbo issue or BPV issue. Maybe your vacuum line routing.

There is no reason to even have the vacuum tank hooked up anymore.

 

I mean that choking you can hear during your warm up cycle that you refer to as sounding bad. Surge is the compressor compressing air not uniformily due to bent fins on the compressor or even missing fins. which causes boost pressure to change and releases charged air through the BPV. You only experience compressor surge under boost though, but since the warm up cycle is kinda partially boost, its not unlikely that you wouldnt experience it. PSI/vac should be around 0 during warm up.

Compressor surge means damaged turbo, I dont think your turbos damaged but the next time you take off the intake, try to take a good look at it and see if it moves in any direction other than spinning.

That choking noise could also be due to the BPV not operating correctly too due to vacuum line routing or a damaged BPV. Wonder if the previous owner tried to put a different spring in it to include spring pressure . Doesnt work that way :/

Again I just want to be clear that what you hear with the K&N intake on has always been there. The intake does not cause that to happen but makes it alot more audible. I will try to find a vac line routing PDF for the LNF motor.

I know theres probably a few on here from others asking questions.

 

Example of compressor surge just so you have an idea.


around the 1 minute mark they show a graph of boost (top) and hp (bottom). You can see that the boost drops when ever you hear a "chirp" and you can see the power drop. That is a really really bad case though so really dont think you have that issue. When you would drive the car WOT, did you ever experience and stuttering or drop in boost pressure even its just a small stutter.

 

I pulled the vacuum line off the turbo as your picture showed. Nothing jammed in there or pieced together.

I have the vacuum tank and hoses sitting in my lap now. All looks fine. Like I said earlier, there is a check valve on the to manifold side outlet port that only allows me to blow from the solenoid side. Therefore it'd make a big difference which way the hoses were hooked up.

Pulled out the bypass valve and it checks out okay. Little tiny shiny specs (metal?) Are apparent on the diaphram and in the turbo inlet. Lots of oil residue in there too. The bpv hose held vacuum so no leak there.

And I have not felt a studdering or hesitation like you describe under wot.

The compressor moves a bit only up and down but I'm not sure how much is too much. Its still tight though.