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So i Have an 06 2.2l 2dr automatic trans cobalt. All stock except k&n filter. Car has 193000 on it. Great car! I am a some what competent diy er with all hand tools but thats about it. Currently having issues with #1 cylinder miss fire, and catalyst system below threshold. started with plugs cause it needed it no help read up on here other stuff to try-cleaned throttle body(was very dirty but cleaned up easy),checked compression 165,170,170,165, no vacuum leaks or intake leaks, found cracked stock exhaust manifold. Also o2 sensor #1 is an odd looking shape like it has gotten way too hot! So my questions are #1 does anyone have a stock 2.2l exhaust manifold w/o a crack in it they want to get rid of? #2 is this whats causing #1 to miss fire? #3 did crack in manifold melt front o2 sensor or do i have other issues? Car is running good slight decrease in mpg no overheating or any other problems that i can tell. i have a scan tool and can watch my o2 sensors live data. Both front and back sensors are jumpy (indicative of a bad cat) but am wondering if all is from the cracked exhaust manifold and bad o2 sensor(the one that looks kinda melted) throwing everything off? Any help is greatly appreciated. Hope its not a bad cat too im in Ca. and dont even want to know how much new cat is.
 

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Yes, if the crack is close to the block the knock sensor can detect the noise and change timing which might account for lower mpg. This will also give you cat inefficiency codes if not all the exhaust flows through the HO2's
 

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Up in the mountains kinda by Lake Tahoe off of hwy. 395 little town called walker CA. Thanks Coby7 I forgot to mention it is a noticeable miss at idle when cold. After 45 min drive it goes away. Won't always throw a code though.backfires when it misses. My take is ecm getting lean signal from ho2 in turn dumping too much gas for #1. Maybe #1 injector has something stuck in it cause its at end of fuel rail w/no return?
 

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I'm going to be getting a lsj header and zzp dp but I want to keep the stock dp for smog but if the stock dp will bolt up to the lsj header and pass smog I can get rid of the l61 header. Any thoughts?????
 

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yes it can be tuned out will it pass idk iv been asking the same queston for a while now but i think it will fit fine you prolly wont see any gains over stock though. they also have an h02
bung on the header if i remember right. with it passing maybe some one else can chime in with that
 

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secondary air injection its a emissions thing. it blows filtered air into the exhaust on cold starts it can be deleted pritty easly on the l61 but on the LAP which is what i have its harder to get rid of
 

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Don't mean to be rude fellas but ya crashing the "I need help with something thread" take the discussion to random or 09 cobalt thread good info in there!

Sent from my EVO
 

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Any way ace once I get this figured out if you haven't found a header and I have mine out and if I don't need it ill hit you up I know you are in a hurry though.
 

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Cool. Thank u guys for all the info! gypsy ya kinda in hurry. just want it fixed ya know. ill keep u guys posted on my status. bronxknight thanks for the tip for a newbie.

---------- Post added at 07:54 PM ---------- Previous post was at 06:42 PM ----------

secondary air injection its a emissions thing. it blows filtered air into the exhaust on cold starts it can be deleted pritty easly on the l61 but on the LAP which is what i have its harder to get rid of
thank u read newbee needs help with abbreviations that helped alot. now i know i have an l61. does the 06 even have sai. from what i see nothing to get filtered air to the exhaust.
 

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You shouldn't have SAI that was like a 07 and above thing. You can easily tell by looking at your air box in the engine bay. If you have a small tube on it you have it, if not then no

Sent from my EVO
 

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Crack in exhaust manifold can cause the o2 sensor to think the car is running lean and it will add fuel. I dont know if it can melt the sensor but excess fuel can burn in cat and destroy it relatively quickly.
 
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