I have been noticing, especially on colder mornings, that when I start my car, after about 3-5 seconds, the engine sputters, makes an unusual noise, drops RPMs, and then revs back up to normal. It seems as if the the car almost loses power, then gets it back again? Any ideas?

NO mods except K&N filter.

 

Sure the maf isn't fouled by the K&N filter oil?

 

hah...i wish that was the only issue my car has at idle!

 

k&n filter shouldnt cause issues with the mass air flow sensor, unless it was over oiled.

 

SEE THIS THREAD: https://www.cobaltss.net/forums/show...hlight=strange

As a victim of this issue myself I'm pretty sure that it's oil starvation at the Cam Phasers.
It's still a theory technically as I don't know for sure but mine went away after changing the oil. Now it's back a little bit now that the oil has some miles on it.
Change your oil and filter and let us know if the problem goes away. If your oil is *new* - as in 85% or higher on the life monitor then my theory is shot. Pay particular attention to the filter. See if it looks unusually dirty or even if some pleats were crushed in like they were on mine.

FYI: I cleaned my MAF before changing my oil with no effect. It's not the MAF.

 

It has been doing it for quite a while now, like this morning. it only does it once. i can shut it off then recrank and it does fine. i changed my oil, cleaned the maf, and just put the k&n in about a week ago, and it still does it. could it be plugs, even though i'm untuned, and at less than 30k miles?

 

I know this, thus, "sure the maf isn't fouled by the K&N filter oil?"
I'll try to be more specific next time

FYI, some people have received over oiled K&N's before from the factory.

Pull the plugs and see or take it to the dealer and let them tinker with it (if you have a trustworthy service dept).

 

There's 48 posts on this thread with all kinds of ideas and NO definitive answers. I think the best advice is learn to live with it till the car goes out of warranty.

https://www.cobaltss.net/forums/showt...hlight=strange

 

How many miles on the car? I see just K&N, no tune then correct??

 

mine does that sometimes...

 

Mine has had a rough cold idle and cold start studder for a couple months now. O2 sensor going bad might be your issue.

 

^This is getting to be an insane amount of people with a relatively new car and bad front O2, isnt it?

 

Yep, it might be a heat issue from its location on the exhaust housing of the turbo. It might be faulty sensors, or it might be something else entirely. We do not know yet. Hopefully there will be an open recall for this if it starts getting out of hand.

 

Not so sure mine is as bad as others yet, but it's likely going that way. Fuel trims have been strange for a while now. LTFT's dead on one day, +5 the next, -2 the day after. Same commute. Could be the intake and the humidity (rain or snow) but gotta rule out some things since the K&N SRI hasn't been released yet to try.

 

We all seem to be geting that same O2 code though.

 

Huh? Linky broke.

 

My car does this sometimes, and one time it did it and totally died WTF?

 

There has to be a common link, besides "It's a cobalt, or its a LNF". It does seem to do it more when colder, and the colder it is, the more obnoxious sounding and acting it is. Today my car sat at work for nearly 9 hours, and it didnt do it when I cranked it. It was mid-high 50F. Once I got home, I washed my car, cleaned my engine bay, and rechecked all my brakes, which all in all took around 2-3 hours. I cranked my car to let the engine dry, and what do you know, it does it, but it's not nearly as loud. At this time it was high 30's to low 40's. In the morning, it gets down to low 20's or so, and it's much louder. I cant imagine what it does when it gets to be the teens, and lower for some people.

I'm curious, RYRO how cold was it when it died on you?

 

http://www.youtube.com/watch?v=6gQjHSPqJWg

Is that what your referencing as the noise? If so. Look at this thread

https://www.cobaltss.net/forums/2-0l-lnf-performance-tech-153/strange-issue-cold-start-up-194165/ but i think someone already posted a link to this, if so, im sorry in advance

 

Yep, that's the link I left earlier and the other guy tried to. That's exactly the issue in that video.

I know for me... ok... it went away for a solid 4 weeks after changing my oil. The oil filter didn't look too good at that time. But the poster of this thread says the oil is new along with the filter and his still does it. So now I don't know what to make of that.
Mine started doing it again recently. I'm going to change the filter here soon and see if it goes away.

But the OTHER thing I wanted to mention about getting worse when it's cold, etc. That is very true. Maybe others will find the following to be true for them also. When it gets colder it doesn't mean my car will do it more often. It means that if it does it, it's more severe. For example, it did it earlier last week when it was in the 30's. It's done it this week too when it's in the 20's and teens. Tonight it was only 9*F when I started it after sitting for 9 hours and it didn't do it at all.

It's really bizarre. I'm sure it's not a MAF issue do to oil contamination. I've had my K&N nearly since the day I got the car and I'm at 37K miles now. I cleaned the MAF (used MAF cleaner and let it dry) about a month ago. Which by the way, was about a week before the oil change. It still acted up during that week following the MAF cleaning. I checked the filter but it looked good yet so that hasn't been messed with.
I'm not ruling out an O2 sensor but if it were that skewed wouldn't it throw a code? And why only for a few seconds after a cold start? What's different about it at THAT time? Unless like we were thinking about oil suddenly engaging the cam phasers. Maybe after a few seconds the exhaust gases hit the primary O2 sensor and it makes a sudden adjustment away from the baseline.... ? Sound possible to anyone?

I'm addressing everyone, just trying to generate some ideas.
I did take mine to the dealer. Miraculously the car never had a dip in idle while they had the car for nearly a week. They tried it each morning and late in the afternoon. That really frustrated me because it had been doing it to me pretty much every day! They did hear the noise (without a rough idle) and said it was the high pressure fuel pump. They said it was normal and not to worry about it.
I still have a problem with that because of how random it is and how much the severity of it varies. If it were normal wouldn't it at least be consistent?

It's a very confusing situation that affects a lot more of us, tuned and stock both, than I thought.

 

See your just as curious as me, since mine does the same exact things when its below 32 degrees out, I had the dealership look at mine, Saying the same that it was my "high pressure fuel rail" and nothing they could do about it.

 

Ok, I am going to add to this. I have a brand new 2010 Cobalt SS with ONLY 300 Kms on it.

It does exactly the same thing in the morning. It does not take it long to settle down, but for about 8 to 10 seconds, the RPM's are searching and the tach needle definitely goes up and down. My solution.....Plug in the block heater overnight to keep the block warm, then you have good starts in the morning!

LOL

 

The block heater option is mostly for the owners up in canada, most of us in the states do not have a block heater

 

Cold Quebec winter and starts no problemo with stable idle

 

Actually, the Block heater option is NOT an option at all for any turbo cobalts....I just had one added after the fact.

They definitely help on cold mornings thats for sure!