So, for a while now my car will intermittently suddenly start running like crap... buck hard under throttle of any kind, reduce boost to between 0-5psi max, and occasionally backfire.

I first noticed it shortly after making some modifications... I installed a K&N SRI, Forge VTA BPV, and did the vacuum tank bypass. I also had my Trifecta tune updated for the new bolt ons. In addition, I already had a Catless DP and GMS1 sensors. The symptoms were very bad during this time, the car would frequently lose boost and buck violently if you tried to accelerate.

After a lot of attempts to datalog and troubleshoot the problem, I decided to return the Forge BOV, take the K&N intake off, and go back to GMS1 tune. So, I went back to GMS1 and the car ran good for a week or so. Eventually the symptoms started again and became more persistent. I reflashed the car back to my original Trifecta tune for just the catless DP with no change.

Where I'm at now is the car will randomly loose boost, intermittently run terrible at light throttle and idle, and throw a CEL for P0101 (MAF sensor performance) and P2188 (Too rich at idle).

Anybody have any ideas as to the cause? Could it be a bad or dirty MAF sensor? I do have a K&N drop-in which has been in there for about a year now, maybe the oil got to it? Or is it more likely to be something like a boost leak.

Any help is appreciated!

 

Cleaning a maf is easy. So id start there. Just buy the right cleaner. Maf/sensor cleaner spray

 

Sounds like intake valve gunk to me. You'll have to clean the valves off.

 

borescope valves/ engine leak down test/ditch the k&n

 

how much mileage do you have? keep us updated. hopefully it's not the valves. i worry that will happen to me one day. Damn direct injection valve killer. so good it's bad :/

 

I had the same issue twice.
First time my maf sensor was shot (possibly from running k&n filters) sensor was shot. Second time my intake vaccume line broke off (stock crap intake)

I think it's your forge VTA that was originally causing your issues though unless you have a maf relocate it will screw with your fuel trims heavily. Since normally the bpv vents measured air back into your intake. You are successfully dumping measured air into the atmosphere and not telling your car it's gone so fuel trims try to do the impossible and compensate for being extra rich but without a measure of how much fuel to take away. It makes the car run rough.

Start with your maf. It's likely the issue regardless of what's causing it. Clean it and you may solve the problem either way. But the tvs won't play friendly with the maf unless you relocate it to post turbo.

 

Thanks for the info guys. I'm gonna start by getting a stock air filter and cleaning the MAF sensor. Hopefully it's not the valves. As far as the MAF relocate, it's not, but when I had the VTA I was on Trifectas new Tune (ECP?) which is supposed to allow you to run it. I datalogged several times, including when the car was acting up, but Vince said everything looked fine.

Mileage is 58k give or take.

Only other thing is my PCV nipple on the stock intake broke a while back, so the PCV line isn't connected to the intake, but I can't imagine that causing it. Not sure if maybe the vacuum tank bypass could either?

 

Gunked valves would not cause intermittent loss of boost. Stumbling, running like crap, and misfires yes.

Just put everything back to stock and fix the pcv nipple and go from there

 

Also if you're still rocking the spark plugs that came with the car from the factory I'd be replacing those with a new set.

 

Any good way to fix that nipple without buying a new factory intake?

Could this be a boost leak? The only reason I didn't think it was is because it's intermittent, although more and more regular now, and I figured a boost leak would be constant. When the car is running smooth and I accelerate hard and boosts and holds 24-25psi like it should.

 

You could epoxy it. The dealership broke mine on there different occasions. Epoxied it twice and replaced it afterword.

 

broken nipple is no bueno...but valve gunk unless you upgrade the pcv will be an issue. if nothing is done EVERY DI motor will coke the valves. eventually. using good tier 1 gasoline, low ash motor oil and a good driving cycle will postpone it. UPgrade the PCV when the valves are clean and then you have a chance of not having to clean them again.

 

Looks like the final diagnosis is gonna be just a dirty MAF sensor.

I finally got around to cleaning it, and after 3 days of driving the symptoms haven't come back. I also switched back to a stock paper air filter to avoid future oil contamination. I didn't really believe the K&N could have oiled up the sensor that bad, but it looks like it did.

 

Maybe having my k&n sit in my closet for a year before putting it on helped haven't had issues yet. What about switching to an AEM dryflow type of fitler that doesn't use oil?

 

Keep in mind it took at least a year for me to have issues.

I used to have a Dejon SRI with an AEM dry flow filter. That filter never gave me problems.... The intake itself was another story.

Honestly, I'm going to stick with the stock paper filter. For the "gains" you supposedly get from an aftermarket filter it's really not worth the trouble.

 

The fix for a broken nipple on the stock intake is posted in the how to. It takes about 5 minutes.

 

Maybe the gains aren't huge but you have to love the K&N SRI sound.

 

I'll take look, but I forgot I had already kind of Mickey moused a fix.

 

https://www.cobaltss.net/forums/how-...r-hose-273968/

 

I have had this very issue for years. It comes and goes for me. Sox-fan noticed that I had the wrong o-rings on my GSM1 sensors, which have been replaced. That had the car running better for a bit, but I still need to get Powell's air-to-oil seperator to keep the oil off the sensors (and out of my damn intercooler). Everytime I tried to get the stealership to fix the issue, they would test the MAF sensor and say it was bad. I have had 4 MAF sensors in my car in like 5 years of owning it. When my car acts up, I usually just pull the battery for a bit and its back to normal. If it keeps coming back I pull the MAP sensors and clean the oil off of them with MAF cleaner as well. HOT AND HUMID air are my cars worst nightmare...

 

To revive this thread, my car has occasionally continued the original symptoms. Since getting GMS1 years ago Ive had the lower MAP replaced twice by the dealer because it blew. I'm getting similiar symptoms again now except worse. On a couple of occasions the car has stalled and wouldnt restart. I was continually getting MAF codes, so after cleaning it a few times I finally replaced it. The driving has improved, but it has had the stalling episode again and refused to start for about 5mins. Now I'm getting the MAP symptoms, erratic Vac/Boost at idle in neutral, poor boost (used to be 25psi on Trifecta, now its 15-20).

Rather than take it to the dealer I finally got around to checking it myself, seeing its out of warranty. The top MAP sensor (in the intake manifold) was a little oily, so I cleaned it. The bottom MAP was clean, but it seemed very loose compared to the top when I undid the bolt. The top MAP after removing its bolt was still snug and needed some force to be removed from the intake. On the other hand the lower MAP was flopping around after removing its bolt. I noticed the top MAP has a blue O-ring whereas the lower MAP has a green O-ring.

TommyK is that the wrong O-ring? I know you said you had that issue...? I remember there was a thread a while back about this but I cant find it. Im wondering if this was my problem all along.....? Im going out now, we'll see if cleaning the top MAP helped at all, if anyone can answer the O-ring question or direct me to that thread thatd be great.

Thanks!

 

I had the same problem with the wrong o-rings on both of my map sensor after my gms1. The green o-rings are the wrong ones for sure. They should either be blue or black. I ordered a few new black ones from tom at ced. And after install the sensor was good and tight in the lower charge pipe. As well I picked up a few extra pounds of boost. Due to the fact that both of my sensors were leaking boost with the green o-rings on the gms1 sensors. I would change the seal on the lower sensor and see how that goes from there.

 

Thanks! It's running better after cleaning that top MAP sensor, back to full boost. I'll definitely change that bottom o-ring though because it's definitely way too loose.

 

The green is okay for stock sensors. Not good for 3bars.

 

My 2006 Cobalt SS Supercharged is idling like **** from time to time and as im driving my car is bucking ! and today it stalled ! Already changed my Map Sensor & Maf sensor ! Has anybody else found the cure for this issue ? it's becoming a real pain ughh
I am a new member trying to figure out this site so i can get someone's help the garage has drained me lol