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I bought a used 05 cobalt 2.0 sc around 3 months ago, from the beginning I've constantly been replacing parts to get the car up to par. My current battle is agents normal operating temp range misfires and slight engine vibration. You can hear the miss from the exhaust and I've about fully extended my wallet. The cars bone stock except for a typhoon cold air intake. Parts I've replaced would be maf, upstream o2, camshaft position, cleaned throttle body, new head gasket and intake, new timing chain, fuel filter, new plugs gap .32 nkg, new air filter, cleaned grounds, new battery, I've about given the car the whole once over. The only thing I've been able to do that seemed to even it out was to disconnect the pcv hose from the valve cover which connects to the cai and suck air from it. In my opinion I find that quite odd but I'm in uncharted territory for my knowledge. Any help would be greatly appreciated, I also have a snap on diagnostic scanner so I can provide sensor data, I'm just unable to Interpet it.
 

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List the codes for us.
 

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So far I've only had a p0300, it causes a check engine every once and a while, as for when it's off I can watch the missfire data, once it warms up cylinder 2,3,4 go to missing. I've changed the coil packs and injectors around with no change in the misfire pattern. I also did a compression check left to right it's 150,145,125,150.

---------- Post added at 01:05 PM ---------- Previous post was at 01:03 PM ----------

Also once around 1,000 rpm and up it stops missing?
 

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Almost sounds like its way to rich. That would explain the unmetered air helping it. Have you watched your a/f ratios?

Did you get the head checked over when you did the gasket? Also I've seen coolant temp sensors act up and not set off a code. They can make a vehicle flood itself
 

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No stupidly I didn't have the head checked, but on the good side I haven't lost any oil or coolant. It's not soo much unmetered air as it is taking metered air away if that makes sense lol afr seems to stay at 14.7, I also noticed my lower bank o2 sensor doesn't fluctuate really, it stays about 788
 

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The rear o2 should move. It might be getting bad. My car lost 7mpg when it failed
If you're pulling a hose off the intake and it smooths out its usually because the vacuum in the intake sucks in the air it wants.
 

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It's the hose the runs to the back of the valve cover that acts like a pcv, when I unplug it from the valve cover there is no change, but with the hose still connected to my cold air intake piping If I suck a curtain amount of air from the cai tube the motor evens out.
 

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Is there a pcv valve there? I'm not super familiar with the supercharged cars
 

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No it's just a tube that goes from the air intake piping to the valve cover, the air moves through passages in the head and block, that's all I know haha. Oddly enough I can have the hose hooked up to the valve cover, unhook it from the cai "without the car running" and hear an air sound when I blow air into the crankcase? I pulled the fuel injectors out and did it again, the air I blew into the valvecover seems to be traveling into the intake. If that's normal I haven't a clue lol
 

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I agree with the temp sensor comment,maybe even a semi clogged converter? Check exhaust temp with your scanner and see how hot its getting.
 

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Did you get the right plugs for your car?
 

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Levee
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Yes I did, what I'm in need of now is live data from a scanner to compare mine to
Where are you located? Also, is the car tuned? I know you said it's stock, but most ss balts are not stock when sold. And 99% of the time, just by putting on a CAI onto the FI'd ss's, you need to re-tune. Right now what is happening is the car is getting TOO much free air into the engine for the maf calibration settings in the tune (one of the reasons why you need to retune with an intake). What you need to do is have someone either look at the tune to see if it's stock/tuned before, and re-calibrate your MAF and MAP sensors to accomidate your CAI, or you will forever spend everything you have trying to replace parts to figure out what is going on.
 
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