Hey guys, I need an idea as to what might be going on before I head off to the dealer.
Wednesday morning, I went wot in 4th gear to pass a semi and for a few seconds the car seemed to push really harder than normal.
There was this weird rush in boost, then I hear the BPV release the pressure (at that point I'm still at wot at about 5500rpm) and I lost all boost... The car would then only boost at app 10kpa (2 psi or so).
At that point, confusion subsides and turns into sheer annoyance. I'm thinking a hose or something.
I head off on my business trip with the company car and when I got back at night, I was expecting the car to have no boost just as it did when I left. But as it turns out, it was now ok. So I drive home, driving slower than my mom not taking any chances thinking i'd get the car to the dealer in a day or two.
Today, I drive to work, again not pushing the car. By noon returning from lunch I decide to push it and see what happens.
Well to my surprise, it litterally jumped and reached 20psi, I didn't expect that one bit.
I did a few second / third gear pulls at wot, the loss of boost did not reoccur and the car was litterally flying. I won't say it wasn't fun for a few seconds there, but it was worrying nonetheless.
Coming back from work, when I cleared traffic and wound up alone, I tried again to see how it would do. It then got up to app 180 kpa (26psi) at wot. The thing was crazy fast for 2-3 pulls, then I went back to 2psi just as it did on wednesday morning.
So : what the **** is going on ?

 

I am jealous I paid to have someone tune my car and I boost at 20. looks like the secret is out .

Bad ECU, Bad MAF? not sure maybe possessed by the devil. I would haul that to the dealer now, not sure i would want my car boosting 26psi stock.

 

Im pretty sure the 2psi part is limp mode, not sure why though, but think of this as a free bump too

 

Yeah, for a minute there I thought I had gotten a free tune during my sleep...
5 mins later, I'm on 2.0 n/a mode and I get owned by an Aveo
I'm thinking ecu rather than maf... how could such dramatic variations in boost be influenced by the MAF ?

 

I guess all the super tuners on this forum took the night off? Maybe santa clause brought you a tune in the middle of the night and the grinch is trying to steal it back?

Bump

 

I'm no tuner let alone a supertuner but my advice would be go to the local Auto Zone or w/e and have it scanned for codes. Then go to the LNF section and check out the sticky on LNF cel codes. Should give you an idea of what's up.
My guess would be a wastegate or bpv issue-*DISCLAIMER*-lol

 

Ure issue is either of these. Bov, wastegate, the boost solonoid, cat is clogged if u have one. ...

 

I'm stock so no bov issue. I'm off to the dealer now & I hope they figure it out promptly...
I have yet to hear from anyone who's had such an issue with the TC.
I'll let you know how it turns out.

 

I'm interested to see how this one turns out..

 

I am curious to see what they find, but the above is exactly how I feel when the GMS1 goes into "wig" mode.


I've gotten pretty good and unplugging and reconnecting that bottom sensor now - always seems to solve the problem - well, short term, anyhoo.

Good Luck w/ your problem !


Britt

 

It's safe to say that the low boost condition is the result of an over-boost code being set. It is most likely limiting throttle opening as well as keeping the bypass valve open. These are safety measure to keep you from boosting to 26psi because something else is broke and not controlling boost properly.

 

What Matt said. You should not be spiking that high. The spike is what's causing the ECU to put you into limp mode. Don't reset your ECU, and see if you can get them to give you every code that's stored. You should have the overboost code along with some other codes to give you a clue what's broken.

 

Hope your dealer has half a brain or they might just say you must have had it in competition mode. Jk


Definatley some component they control boost isn't funtioning properly.

 

That's the IAT2 sensor (TMAP.) That is likely what the problem is if it not something to do with the waste gate actuator.

 

Wastegate issue... i'll have more details on monday when it's fixed
They lended me a 2010 1500 crewcab 4x4 sierra which could not be more convenient; I have a shitload of crap in my yard I need to get to the dumpster lol

 

Lol funny

 

Had the same problem since day 1 of GM dealer installing Stage 1....

They cannot seem to find the problem, they just keep giving me the car back with nothing done to it..

I hate GM..

I always loose boost when on the highway with minimal throttle in 4 or 5'th gear. Wastegate goes crazy and opens and close and etc... already changed my turbo but did not solve the problem.

Yay for ultra intermittent problem (maybe once a month).

 

Yours is the IAT2 sensor. There are a bunch of threads with the same issue.

 

hmm. i wonder if the forge bvp will solve all those problems.

 

Got the car back... not sure it's ok, it still boosts more than before (up to 140kpa), just not as much as it did and it doesn't go into that sissy automatic aveo tune mode anymore.

Wastegate sensor isssue or whatever i dunno, i need to look at the invoice for the specifics, i'm still rather noob with turbos.
The technician noted in my file I had a "intake modification"... they argue they found water on the sensor. I have a freakin K&N, they call that an intake alteration to the airbox.

I was quick to reply that with the filter box is not modified in any way, it's adequatly closed and sealed and if it makes them happy, I'll switch to an oem filter. I made a point of saying that when I got the car back, it was still boosting high from the gitgo and that it was now a new sensor. No water could've then gotten in it because the intake was taken apart, dry and it was totally dry outside

Anyhow, now when temps reach -10 & the car is cold, I can't get the gears out. That, to me, is far worse. I practically have to knock the gears in & out, then try to run them each one after the other... like there was ice in the transmission or something.

I am getting extremely annoyed.

 

The transmission cables on these cars ice over during the night.

 

It's been down to 15F here already, and I have yet to have any gearbox issues.

 

How so ? I'd like to understand how it happens so I can back up my claim.
It never did this before & it's the car's 3rd winter

 

Someone on here last year posted a pic of their linkage in the morning and it was iced over right where the cables meet the transmission. I don't live in a cold area, so I am only passing on information.

Here's another thread on it: https://www.cobaltss.net/forums/2-0l...-issue-235913/