So over the last month or so when I start my car in the morning to head to work my car will fire up and instantly start to stumble and stalls out. It will stall normally TWICE in a row. Which reqally is very aggrivating. It only seems to do it every other day. And there is no check engine lights on and there are no vault codes when I check using torque for my phone. I'm really surprised that a car can choke it self out and stall twice in a row and not fire any check engine lights. Does anyone have any idea what the problem COULD be caused by ? I had thought a few weeks ago it was my kn sri causing the problem. So I took it off a week a go to clean the filter. And the car still stalls even with the stock air box and stock air filter. My car is gms1. But thats it really. It seems ever sense I blew my charge piping off a month ago I have had the cold start issue. I don't know if that can be realated at all. How ever the car works great besides the cold start stalling.

On another note that MAY be realated or may not be. With my stock air box in plave with the stock air filter. My fuel trims seem to be a bit unhappy. Or so i think. My stft bounces around from -7 ish to +3 or 4 ish. While my ltft stays a very steady -9.3 . And this is totally stock other then gms1. Every once i awhile if i am barely pushing on the pedal. Like maybe 1/8 of an inch or so. I can see my stft drop to -10.8 ish for just a split second . The car stumbles very lightly and then the stft settles and it acts normal. It only does it when I barely push the gas pedal. If I am at any other pedal position it doesnt happen like that at all...

I really need some help on the cold start issue !!

Thanks for any help you can give !!!

On a bright note torque is telling me my car has 271 hp and 288 trq.. !! If that is atll accurate !

 

My first thought was evap purge solenoid but most times it throws a code. You sure you dont have a leak still around a charge pipe?

WIth stock air intake you should see around 0 ltft or slightly negative I think

 

all points to a boost leak somewhere. when i had a massive leak my LTFT went -20+ and the car would stumble to the point I had to give it gas to stop from dieing. Check intercooler end tanks and do a boost leak test

 

I havn't checked for any boost leaks yet. But it seems to build about 18-20 psi and holds it fairly well. But I really don't know. I could have a leak. But I would guess if I do it would be fairly small. Just this Saturday whenit was really hot out my car was holding 21+ psi and blew my charge pipe off again. Would it do that if it has a boost leak ? And how would I check for a boost leak ? Could that really cause all of these issues ?

 

oh yeah, a nasty vacuum leak could possibly do all what you say. However you are holding boost pretty good.

To test for Boost you need to build a boost leak tester. its around 15 bucks in parts from Home depot. Look for SSlobalt on here, he has a link to it in his signature.

 

I will search his name and check for any leaks. But in all seriousness i'm leaning towards there not being any. If they were of fair size to cause I problem with start ups I would think that the perforamce of the car would be off also. But the car seems to work well. And it has reached levels just this saturday of 21-22 psi and blew my upper charge pipe off the intercooler for the second time. I would have thought any decent boost leak would not allow that kind of high boost.

Lets just say for a second that I don't have any boost leaks and that my intercooler end tanks are okay. What ELSE could possible cause my issue on cold start. Not to mention my ltft. I would really like to know what is up with that. I would like to see what term or someone else with some good tuning noledge thinks. Like that cobaltcss1 guy ! They both know ther stuff. And I am just begining to get into these cars.

 

Well it's really hard to say. Do you have any other symptoms? Misfires, knock retarding, etc

Vacuum leaks around intake or other vacuum lines. Has the evap purge valve on the intake manifold ever been checked? It's super easy to check.

You can still hold a lot of boost even if you have a small boost leak. If you keep blowing the charge pipe off that just tells me your clamping isn't doing its job which could mean boost leak or you are installing incorrectly.

 

Why does your charge pipe keep blowing off at 21 PSI? You running stock piping and clamps?

It's pretty likely that it's coming loose gradually, causing issues, until if finally just comes right off completely.

 

^^^^^ Exactly.

Sorry if I came off as rude in my last post, not my intention. My charge pipe came off in the first 6 months of having GMS1, but hasn't in 3 years.

 

I don't think I have too many misfires that I can see on torque. Maybe a few. But from what I understand that is fairly normal to have a few misfires as long as they arnt consistent. The stupid clamps on the injen upper chaarge pipe keep slipping out of the silicone coupler. I might try adding a second coupler to see if it helps any. At 21 psi it holds. Most of the time at 22 psi the injen charge peipe will blow out of the silicone coupler and the coupler stays on the intercooler.

I have tested the purge solinoid on the itnake manifold. And it seems to be good. I cant blow through it. And I can hear it working ! Im stomped about the car stalling and not setting an engine light !

What should my fuel rail pressure be at idle on cold start up ? I only took a qwick look at it on torque. It looked to be bouncing around 400-600 psi. But i will double check it next time I start it.


I am running the injen upper charge piping. And it has blown off twice at wot in the lqast month or so. I think it might be qworking loose over time like you said. Because when I loosen it too put it back on. It already feels fairly slack compared to when I put it on. Im going to try and put a second clamp on. I am just using the clamps ( worm gear ) that came with the injen. I have never had the other stock charge pipe blow off.

But my real issue is the cold start up and stall from time to time !

 

I had the same problem at 24 psi. buy some T-clamps from silconeintakes.com and be done with it. The ones they give you with the injen are crap

 

I'mm deffinitly going to be fixing that issue asap. As well as I will try to boost leak test the car. Does anyone know of any other reason that could cause the car tpo spit and spuuter and then stall out on cold starts ? And also , does anyone know the fuel rail pressure at both idle on cold start up and at wot ? I kind of want to look at that too trough torque.

 

So a little bit of an update. When I left work as usual lately my car stalled and kinda ran like crap for the first 5 seconds or so it started up. I still do not have a check engine light on. However I know ( which i did not for sure last night ) have a fault code I can see in torque that was not there last night for sure. It says it is a p0497 ?

 

Evap system.

Purge Valve
Purge Valve
Purge Valve.

or possible vent valve

I have had the same code. On my 3rd purge valve at 60k. Eventually you will get a CEL if you don't reset the codes. Takes a few drive cycles to set off the light.

 

Which one is which ? And which one does that code refer too ? It says when I google it emmisions system low flow ? Or something to that effect. I cant afford to replace both the one in the tank and the purge in the mani. I wonder which one is bad ? lso , when your purge valve went. Did your car give you problems on cold starts only like mine ? And lastly. COULD the bad whatever valve cause my ltfts to be at -9.4 ??

 

THere is a little black box on the front of your intake manifold. take it off and see if you can blow through it. if you can, your EVAP Purge solenoid is bad. Replace it



It is right next to the MAP sensor in this picture

 

I have a couple threads referring to the issues I had. They are the exact same as yours. Cold starts were a horrible thing. Large LTFT swings.

Evap purge valve is on the intake manifold and it's where I would start.

Here is my original thread. P0497 is the same I had.

Remember when you test it, if you blow through it it's bad, if you can't then it still has the possibility of being stuck close.

It takes about 5 min to replace and like 20-30 dollars

https://www.cobaltss.net/forums/prob...-p0497-238059/


To test and replace

If you want to see my stupid mug.

 

I tested it a month ago when my problem first started an I couldn't blow through it then. But I will double check again. If I can't blow through it. Would that mena it woul be the vent valve in the evap canister by the gas tank ? If o that sucks. GM changed the part and it requires a new pig tail to hook up to the old harnes with the new sensor. Plus I unhooked it one morning and I think the car still stalled out. But I can't remember ! Im hoping i can get this figured out and that it is the cause of my wacked out fuel trims .

 

Or even worse... Can the purge valve solinod work on and off ? Work one day and then not the next?

 

If the charge pipes are blowing off that tends to tear the rubber hoses which causes leaks and also means clamps are not tight enough to begin with which means leaks. Definitely do a boost leak test that -9% LTFT plus a -10% STFT (-19% total fuel trim) as you roll into the throttle points to a leak for sure. Stock airbox should be close to 0.0 LTFT. The car will still try hard to boost 21 psi or so like commanded which will over spin the turbo if you have a leak and do not fix it. A big leak will throw a P0101 code and an underboost code and a rich code but it takes a decent sized leak to do that. Purge solenoid could be bad but normally that causes the A/F to sine wave rich then lean. With GMS1 the MAPs are prone to leaks especially if the wrong sized O-Rings are used or if the O-Rings are damaged (cut or pinched due to not being lubed or being forced) during installation.

 

Cap off the nipple on the purge solenoid with a Vacuum cap and a clamp or zip tie (needs to be secure no leaks) and just let the plastic line breathe to atmosphere. Disconnect the battery to reset the fuel trims and then start the car and see how it runs for the next 4-5 days.

 

[QUOTE=Terminator2;7061052]If the charge pipes are blowing off that tends to tear the rubber hoses which causes leaks and also means clamps are not tight enough to begin with which means leaks. Definitely do a boost leak test that -9% LTFT plus a -10% STFT (-19% total fuel trim) as you roll into the throttle points to a leak for sure. Stock airbox should be close to 0.0 LTFT. The car will still try hard to boost 21 psi or so like commanded which will over spin the turbo if you have a leak and do not fix it. A big leak will throw a P0101 code and an underboost code and a rich code but it takes a decent sized leak to do that. Purge solenoid could be bad but normally that causes the A/F to sine wave rich then lean. With GMS1 the MAPs are prone to leaks especially if the wrong sized O-Rings are used or if the O-Rings are damaged (cut or pinched due to not being lubed or being forced) during installation.[/QUOTE

I know all about this lol

 

Well I just took the purge off and I CAN NOT blow through it at all. No matter how hard I try it holds pressure. And I was blowing with all I had !! On a serious not. It seems good. So where does that leave me ? The actual charcole canister being plugged ? A bad vent valve. Which might I add I have not heard the evil monkey in the trunck in a month or so. Which I always assumed was the vent valve opening and closing and cycling open and closed ?? My other issue ( TERM. ) sense you mention my super great fuel trims. My torque app on my phone tells me my cars commanded afr it wants is 14.7. But its measured afr is floats around 13.8 to 15.8 non stop. It just bounces all over the place. Or is that normal. Or am I going to blow this poor lnf up ? It really does work well. Most of the time. It seems like I have two issues here maybe ? I could get better fuel trims then -9.4 with my kn sri back on. I took your avise and took it off for a week or two and decided to clean my filter why I was at it. But now all of this.. FML !!!

 

Well the P0497 would not be anything else but an evap problem. And I still think it's the purge valve. I have had a bad one you can't blow through. Could be stuck closed.

You need to test with the evap unplugged or capped.

I'm guessing it fixes all of your issues. I would start there too because it's the easiest. At this point it would be preventative maintenance to replace anyway.

 

I would say may cold start issue for sure is caused by something in the evap system. But what part Idk. I can't blow through it. And I can still hear and feel the purge solenoid open and close very fast when I start the car. My concern is spending money on the wrong part. The message online for the DTC said evap LOW emmisions flow. of course that was a general description and not specific to our cars. I am still stumped which part to get first sense my purge valve APPEARS to work. And I really hope fixing the evap issue fixes my fuel trims. I will try to find something at my house to cover over the end of the purge . I don't have any vac caps.