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Discussion Starter #1
Hey guys, new to the forum and need some help.
I just picked up a 06 GTO and the CEL came on before I could get her home.
P0300 random/ multiple cylinder misfire and a
P0151 bank 2 sensor 1 circuit low voltage
The car has a 408 build on factory block with 15k miles, small ls6 cam, dual springs, factory heads, intake, TB and injectors. Long tubes, catless.

I am not feeling a misfire when the light flashes.. also when the motor is dead cold it will not start and stay running unless I blip the throttle to get it up to 2k rpm for a second. Could this just be a tuning issue?
I allready changed both upstream 02s and new spark plugs but still getting the multiple cylinder misfire.
any ideas would be greatly appreciated.
 

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If it is tuning, i would be worried that the previous owner ran it 15k miles like that.

I also would think the o2 CEL would be a seperate issue.
 

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agreed, id be concerned too, but it wouldn't hurt to have a tuner that you trust look things over in it. Other things you could check would be compression, pull the valve covers and check the springs out make sure one didn't break.
 

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Discussion Starter #5
So the car was from. North Carolina and its winter in Massachusetts here. Maybe that could make a difference?
The springs are good as far as I can tell. They are a dual spring.
02 sensor fault has not come back since replacing them.

I think I'm just going to throw a bigger cam and injectors in it and send it to my local tuner.
Any suggestions?
Thinking fast 46lbs injectors and maybe a BTR4 or texas speed ls1 stage 4 cam? Heads will be ported later
 

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if it's in the lower rpm ranges, like teens and lower 2000ish, it could very well just be the cam. you just need your misfire tables desensitized in a few cells. pretty normal for any cam to to that.

the ECM detects misfires using the crank sensor. it basically expects the crank speed to vary by a certain amount due to the power stroke accelerating it a little bit. an aftermarket cam changes that dynamic, and the ECM's ability to detect small variations in crank acceleration is pretty sensitive.

either the bloke who had it before never had that tuned out, or maybe it is a little different now that you have denser air. not sure. i would take it to tuner and see what he says.
 
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