White smoke

2013 GMC TERRAIN
70,000 MILES • 3.6L • 6 CYL • 4WD • AUTOMATIC
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MUHAMMAD ADNAN
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I have terrain 2013
when i start it ok.after 4 to 5 mint its start white smoke with engine miffiring detected p0300.
i replaced piston ring .injector ,spark plug ,new complete cylinder head with new gaskit new exhaust valve and intake valve with valve seal but its also same no any changes what can i do.when remove oxygen sensor it black carbon.
Apr 19, 2017 at 8:13 AM
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HMAC300
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the o2 looks like that because 0300 is a random misfire. have a mechanic scan it and freeze frame it so he can check sensors and other stuff you can check for a vacuum leak and fuel pressure as both will cause your problem see link for fuel pressure. a mechanic should do this on misfires so you don't waste your money on good parts like you have already as well as the time spent.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
Apr 19, 2017 at 9:56 AM
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MUHAMMAD ADNAN
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I replaced also fuel pump assy and regulater but still to much white smoke after 4 ,5 mint while engine start
Apr 19, 2017 at 10:19 AM
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HMAC300
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pressure check coolant system and see if it's an internal leak like a head gasket or cracked head. the white smoke cold be from random misfire as well do like I said in first reply
Apr 19, 2017 at 12:09 PM