AG305

hey there.

im having an issue that seems to be pretty common from what ive seen by searching around on here but i havent been able to find a concrete answer.

whenever i first start my car (be it in the morning or later) it starts right up very quickly but then immediately bogs down and wants to shut off for about a good 5 seconds and sometimes it does but then it settles down and does its whole warm up cycle and its all fine and dandy from there. no CEL or anything.

today what i noticed differently from other times is that as it was finished bogging down a large puff of white smoke came out for a second and thats it. no more smoke after that. it WILL smoke alot on colder days only at start up and then completely go away by the time i get to my destination. it has been a bit on the cooler side recently but nothing like freezing or anything like that. just 40s maybe. once the car is fully warmed up it pulls hard as ever and idles fine. afr and coolant temps are perfect too. theres absolutely no problem other than the first like 5 seconds of an initial start up.

so my question is, what are the known culprits that cause this issue and what can i do to fix it? no vaccuum leaks (that i know of) all connectors are connected. good gas. im at a loss here and cant figure this out

jdbaugh1

iTrader: (1)

Have you noticed a drop in your engine coolant level? If you have a supercharged Cobalt have you noticed a drop in the heat exchanger fluid level?

AG305

no not really any change but ill look again. its an SS turbo. imma try to get a video of it also. might just go do that now.

jdbaugh1

iTrader: (1)

Is the smoke vibrant white or more bluish grey? One thing that would make sense in your situation is worn valve guides/seals. When they are cold they will not seal as well. It should also cause more smoke when you downshift to decelerate and then get back on it. Have you noticed any oil consumption?

AG305

its on the whiter side. not really blue but the smoke goes away completely after its warm. the smoke is only on colder days or when it just rained so im guessing its just moisture or something. no oil consumption or smoke once im driving around.

i also noticed a gurgle from under my dash that im guessing is my heater. its the first time ive heard it and i just so happen to have started driving before it was fully warmed up which i never do. i noticed my temps were like 115F when i heard the gurgle.

jdbaugh1

iTrader: (1)

Whenever I had heard gurgles from the heater core it was in a vehicle that needed the coolant system flushed and the gurgle was from buildup causing a restriction. Wouldn't think that has anything to do with your particular issue though.

AG305

heres a video of startup. recorded with snapchat so towards the end the audio kinda goes quiet for some reason


the car will do that everyday whenever i first start it up. sometimes the car completely dies and i have to start it back up and sometimes there will be some smoke too in which this case there wasnt any. temperature was in the mid 50s when this video was filmed.

the "change oil soon" just so happen to come on right now also which has me wondering if the problem has to do with oil.

jdbaugh1

iTrader: (1)

Sounds like you just have a miss briefly at startup. Shouldn't have anything to do with your "change oil soon" indicator as that should only come up when your oil life monitor exceeds calculated service life of oil. Do you actually reset the oil life indicator each oil change? I have never actually ran my oil life even close to 0% because it seems like way too long to go without at least changing the filter. If you did reset the oil life indicator on the last oil change I would definitely go ahead and change your oil even though I don't think it has anything to do with this issue.

Have you pulled out your spark plugs and inspected them? They could be slightly fouled causing misfires at startup. If you compare them side by side they may also indicate a problem in a specific cylinder.

AG305

yes i always reset the oil indicator. the reason i brought it up is because people were saying something about the oil being too thin or something when its cold.

i havent checked my plugs but im gonna go ahead and do that and change the oil.

how about something electrical or something to do with my tune? this morning it was dark out and i noticed the dash dimming as it bogged down.

jdbaugh1

iTrader: (1)

That's most likely just because your alternator doesn't have good output at really low rpms and possibly you have a weak battery. I'd just check your plugs are clean and properly gapped and go from there.

AG305

so i was able to get to the spark plugs. they definitely look like they need to be changed (brown but not too brown) but i also saw they had a small amount of oil on them. the oil was inbetween the white part and where the threads begin. like a little ring of oil.

AG305

brand new ngk plugs gapped at 32 just went into the car and the problem is fixed! car started right up with absolutely no bog down from a full cold start at like 40 degrees.

i still gotta figure out the underlying issue with the bit of oil on the plugs. my guess is the valve cover and spark plug seals.

AG305

dammit! i spoke too soon. the problem is still there even with brand new plugs.

can a coil be the issue? i noticed when reinstalling my coils one of them doesnt click into the connector like the others.

jdbaugh1

iTrader: (1)

Sounds like if the oil is above the threads it is your valve cover gasket leaking a bit like you said. But as far as what is causing your startup stumbling/misfires I don't have any more good guesses. It'd be interesting to find out what causes the puff of white smoke and if the problems are related.

AG305

yeah im stumped. that puff of smoke was a one time thing that never happen again. no clue what that was about.

since the car runs perfectly fine after that little miss im going to guess theres probably an issue with my ecu not getting correct readings for that split second on startup and it has to relearn the values of my tune or something.

im gonna check my new plugs for oil again and if there is imma replace the valve cover gasket to see if maybe that bit of oil that sits on the plug causes a miss until its burned off. could be the smoke thing too. who knows

jdbaugh1

iTrader: (1)

What tune do you have? There's a possibility it could be a little funky on startup.

AG305

so the previous owner had taken it to Backyard Turbo a couple times to perfectly dial in the tune thats on it now. runs real smooth and real strong at 23psi. when i bought the car it didnt startup like that though.

AG305

this afternoon i started it up and it bogged for longer and worse than ever but what i noticed that i never did before was a very strong fuel smell once the car turned off. i suspect that the car is drowning itself in gas for a few seconds cause it believes its getting more air than it actually is. im gonna have to recheck every connector and sensor including the o2.

AG305

so ive come up with a list of sensors i believe could be causing my issue but since the problem only happens at cold startup and does not affect the drivability or performance in any way some of these suspected sensors might not be a problem. what do you think??

MAF
TPS
both cam sensors on the valve cover.
the throttle body and IAC
coolant temp??

these are all little guys i know can affect idle and like i said, since its only for a few seconds on startup i really dont know if most of these can be the problem because i would think there would be alot more issues while driving and stuff.

AG305

checked my maf, checked my intake, put in brand new stock plugs cause the last ones i put in were a step colder, replaced valve cover gasket. problem is still happening!

ive done alot more research and have decided that theres definitely a problem with my tunes fuel trims during cold loop warm up. i read all about the evap purge and vent valves causing similar issues so i went ahead and ordered new ones along with a gas cap. hopefully thats all the problem was! fingers crossed...

AG305

replaced evap purge and vent solenoids. problem is still present. today i decided to give it some gas while it was trying to shut off and i had to almost floor it to move the needle a hair. it was not responding to my input which i found to be real strange. it did however finally move and along with that came popping and backfiring then all was fixed and car warmed up and i was on my merry way.

i have no more ideas of what can possibly be the issue. it would be great if i had some kind of problem while driving so i can easily pinpoint the issue but nothing! im about to just say screw it and live with it because everything else is perfect.

anyone have ANY ideas at all?? i give up

AG305

so i decided to bring this thread back because similar symptoms have returned but now with other probable causes.

what should the fuel pressure on the rpd read with key on engine off? im getting 12psi and the car wont start and im assuming its because of low fuel pressure.