spikeTC2

Hi,
It's GM Stage 2 kit...dealer installed it co'z of the power train warranty...
thanks for the tip and I will go to performance shop and have them check it and let will feed the outcome..thx again..

Stamina

Not to be a troll, but please post information about the Stage 2 kit you have, because GM doesn't list it, nor does anybody on this forum know anything about it. This is the GM Stage 1 kit: 19212670 Cobalt, Solstice, HHR Stage Kit 19212670

The Stage 2 kit for the SS/TC was originally supposed to be the Stage 1 kit (sensors and tune basically) and include a new GM-designed intake. It was never released though, so I have no idea what you have that was marketed as a Stage 2 kit.

spikeTC2

Well they put my car on chassis dyno,,as usual, the problem didn't happen,just told me never to use traction in summer time....da...the car did very well, the results are: 316 crank hp on 21 lb boost...
A/F @ 11.75...those guys couldn't believe it...told me how'd they done that.....beats me.

All I know is, before I bought the car, the guy who works @ chevy dealership told me and showed me on the internet the GM Stage 2 kit worth $1,998 and told me thats what he got installed in the car....that's all I know.,,sorry I wish i could talk to the guy again..

Stamina

Just another update:

Did another boost leak test and didn't really find anything. Rerouted and inspected some vacuum hoses and worked on redoing the coupler on the throttle body to make me feel a little better.

The car is still doing the random low load / idle stumble. I may try borrowing a new coil pack (and since I'm not getting a misfire code) try swapping it in the various cylinders in case I've maybe got a coil pack getting weak.

I've got no new ideas right now. No boost leaks, does it with a swapped MAF, new O2, fuel system cleaned, no obvious wire frays, and plugs/pistons seem fine... No codes for fuel system, misfire, MAF sensor, MAP sensors, O2 sensor, or anything. It also does it on the completely stock tune.

lockdownlegend

iTrader: (1)

hey...have you ever heard of the vacuum tank delete?
because i did that at the same time when i cleaned my throttle body and im still running good after having similar issues as you. i think i had a leak in the tank or a bad check valve in it because this mod sets the vacuum lines up like the solstice and sky motors which doesnt have the tank. when i did this the car was much smoother in the lower rpms when lightly accelerating

Stamina

Thanks for the thought. Yeah the thought crossed my mind when I was examining and rerouting some of the vacuum lines. I've heard of people doing the delete, and have a friend that did it when he did his turbo swap. I just got my hands on a borrowed new coil pack tonight, so if this doesn't do the trick then the vacuum tank may be my next thing to check.

My thought was that the tank was maybe set up there to provide more vacuum buffer to assist NLSs. The Solstice/Sky didn't have NLS from the factory, and it was added through the tune with their GMS1 equivalent upgrade. The SS/TC came with it stock. It's my only idea on why it's there.

DPveritasGold

I'm having major issues with this. My car will stumble so bad sometimes that I can press the throttle pretty hard and it will just keep stumbling and not accelerate.

I did a boost leak test last weekend to 25 psi and I couldn't hear any sort of hissing except coming from that black hose going to the intake manifold that's about 3/4" in diameter.

I'm throwing P0101, P0106, and P0236 codes which are for the MAF and both TMAP sensors.

Is it possible this is occuring because of the fuel filter 'sock' needing to be changed? I still don't know how you're actually supposed to change it though. If I knew I would totally change it.

lockdownlegend

iTrader: (1)

gold...u probably blew your map sensor on the intake manifold.

Stamina

Alright, so I had some time to devote to troubleshooting today, and while the car is cooling down before I mess with it again I'm going to post up an update..

So my friend's fresh loaner coil pack didn't do the job. It seemed to make things a bit smoother on the #1, but didn't fix the problem at hand. I also pulled, inspected, and regapped (.030) the spark plugs. They otherwise seem quite normal, with no signs of issue.

I removed and inspected the stock BPV. It wasn't dirty in the least, had no oil on it, and didn't look a week old from the factory. No rips, tears, discoloration, unusual signs of wear, etc. I was surprised how fresh it looked.

I pulled one of the hoses off the vacuum tank and routed the air directly between the IM and bypass solenoid, effectively disconnecting/bypassing the vacuum tank. Although it didn't fix the problem, I really liked the difference in driveability and response. It helped with the first gear rubber-banding it's always done, improved throttle/turbo/bpv response, and made the car feel more solid and attentive. I may keep that mod despite it not fixing what I'm looking for.

While on my last drive I noticed that when the car is acting up, the stumbles I hear at idle are associated with a split-second timing advance jump of several degrees. I later also noticed that when the car stumbles during cruising, that it is associated with a brief, split-second timing pull of ~3-7°. I monitored the timing getting pulled while monitoring detected knock and KR, and there was no relation. There was 0 knock and 0° KR when it pulls timing during cruising.

This leads me back to thinking it's something throttle pedal sensor or airload related. I tested the throttle pedal sensor input to the ECU and the ECU showed no "jumps" in the signal at steady state or slow transitions, so that brings me back to a vacuum leak again.

I've done two boost leak tests over the weeks and haven't come up with anything of substance. My only thought at this point is that either something is leaking only in vacuum or the issue doesn't show up at higher throttle (near or in boost) due to the small leak not being that big of a deal anymore with the increased airflow quantity during those times. I'm going to check the IM gasket area and coldside TMAP sensor to see if there are any signs of air leaks despite not showing up on a boost leak test.

rukkee

iTrader: (3)

Any chance that the intake valves are gummed up and need to be cleaned ? Maybe try seafoaming it or your chemical of choice .......or pop off the IM and get a set of picks? Just a thought ..GL with it , hope you find the issue .

Stamina

Well, the engine has about 7,000 miles or so on it I think since being built/installed brand new. I'd sure hope not... :/

Thanks man! This has been proving to be a headache to track down.

rukkee

iTrader: (3)

oh...... sorry man ....I missed the new motor part . Things like this drive me crazy so I know the feeling .

lockdownlegend

iTrader: (1)

well since its new you should seafoam regularly and your valves with be clean like rukkees.
he just posted pics at 47k and im happy with his results since i do the same thing and im at 48k haha.

but goodluck finding issue and please post when you do.

FRQ FLYR

iTrader: (1)

Might sound strange but your issue mirrors the "Stage 1" hiccups I was having for some time; intermittent and no cel's. Nothing made the hiccups go away permanently until I "aggressively" tied the tmap wiring away from the a/c line.
Your garage doesn't mention 3-bars but I'm curious if the CIA piping relocates the sensor /wiring to any degree that might cause interference. If not you still may have a wiring issue down there .

Stamina

Yes sir... https://www.cobaltss.net/forums/08-1...e-swap-271371/

Well, I'll double check the wiring. I made sure yesterday to check that the coldside sensor was tight, but I'll double check the wiring.


Update:

I did a couple logs today and I was able to catch it doing it on the log. The car will be cruising at say 41° of timing we'll say, and then suddenly briefly drop to 26°, and then return right back to 41°... all within a split second. During that time period and just before/after, I saw no noteworthy changes in the MAP reading, MAF reading, Load/Calculated Load, Throttle Position, any temps, STFT, AFR, etc. No registered knock on any cylinder and no KR during the times it does it. I'm like right now. I'm going to try busting another log for myself including a few other parameters to see if I catch any pattern, trend, or connections. I'm going to try catching Vince to bounce some ideas too.

SSlobalt

Maybe the cam position sensor, then?

Stamina

Yeah, I'm going to expand/change my logged PID list to include the cam position sensor and phasing on them for a few logs just to see if something funky may be happening with them that may be corresponding to the issue. Everything I've seen so far seems pretty normal, and nothing unusual or sudden corresponds to when the timing changes and stumbling occurs. I'm even still trying to understand if the timing thing is really a cause or effect to something else.

Still no codes.

Stamina

Just an update:

I noticed some weird exhaust cam phasing activity in some logs I did. During constant speed/throttle at lower RPM (say ~2K RPM), the exhaust cam would unphase either slowly or quickly (perhaps 20 degrees or so) and then suddenly jump back up to a higher phasing setting (while the intake cam wasn't doing this). I also verified it through the RPD (I am rarely on that page). I found that the stumbling occurred during the same times that this unphasing was happening.

I went to the dealer and bought new phaser solenoids (the phaser oil flow control solenoids that go in the top of the head, not the phasers themselves, that go on the end of the cams), installed them, and the unphasing and stumbling problem went away. They were the original ones since my car was new and I have almost 80K miles of use on them now, so I decided to just get both of them.

I never had any codes get thrown for the phasers. It would've made troubleshooting much easier.

turbosmart4

iTrader: (18)

Seriously man.... Same think I've been thinking....

footballplaya3k

iTrader: (1)

So you fixed it?

lockdownlegend

iTrader: (1)

thats good to hear...so all you did was replace those two sensors?

Stamina

Yep, it's fixed. Those two solenoids control the flow of oil to the phasers on the cams. The back one that controls the phasing of the exhaust cam was apparently acting up.

I was also told that the cam phasing was part of how the ECU calculates engine load, so it's possible that when the exhaust cam was unphasing, it caused the ECU to suddenly change the spark advance as well, thinking it was at a lower load, and causing that feeling of stumbling I was feeling.

The findings also make sense in a way, because when the engine is at low RPM and low load (in this case enough throttle to keep the car moving at a steady speed), this is typically when the most cam phasing is needed as well as the the oil pump not spinning as fast, so it put the biggest load on the solenoids and the exhaust one could no longer keep up.

Bleu

Good read. Im going to have to log my car and see if the cam phasing has anything to do with a similar problem of mine. Hopeflly I just need the fuel system cleaned at 55k miles...

SSlobalt

Awesome, Stamina. I can't imagine how hard this would have been to repair without the correct logging equipment. This is why everyone who owns one of these cars should have the ability to log.

lockdownlegend

iTrader: (1)

i know everyone says search but could you list the part number for the sensors?