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I have a 09 Pontiac G8 3.6l with 227,000 miles that recently started throwing a misfire code for cylinders 1,3,5 and the scanner at autozone says bad injectors but I doubt that since i’ve never replaced a single injector in anything i’ve owned. I started with the maf sensor which wasn’t the problem, then went with the cam sensor but I didn’t put on because I leaned towards injectors, should I replace the injectors or what? I’m really lost at this point and can’t find anything on what might be my problem. It’s not all the time but when it does happen the car shakes at low acceleration and when i floor it, it goes away. any advice?
 

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Unlikely all three injectors failed simultaneously. Most recent spark plug change? Ground for the ignition coils checked? Engine scanned for codes? F35 fuse for odd coils/injectors checked?
 

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The fuse that powers up those 3 injectors, also is the power source for the 3 coils on those cylinders. To me, a 1-3-5 misfire condition could just as easily be caused by those coils loosing their ability to fire off. If your sure that fuse F35-20A ,labeled (ODD COILS) an located in the under hood fuse panel is "not" the problem, I think you should take a good look at this >>>>> There is a master disconnect connector located at the rear of the drivers side upper intake manifold. It is black in color an contains 10 pins an mounted in a horizontal orientation. Pin #1 is that supply voltage to the 3 injectors. If it were to develop an intermittent condition, maybe a wot throttle action has an effect on that pin/socket junction. As a reach (in my mind), if the upstream H02 sensor started loosing its ability to produce the required variable voltage signal back to the ECM (but not bad enough to fault itself), it too might be interpreted as creating a misfire condition.
 

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Either there is something in the fuel rail to affect the one side, or full voltage is not going to the injectors or coils. Swapping the injectors to the other sides would give you the opportunity to check the rail for blockage and see if the codes move to the even cylinders.
 

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^^^ Bear in mind this is a V6 thread.
 

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bad upper intake gasket
So I just had my G8 in for service for something kinda unrelated. I had a coolant leak so had the thermostat and thermostat housing replaced. Which means taking off the intake and replacing the gaskets.
I get the car back and it's throwing the misfire code on cyl 6 now and dealer says it is unrelated and they could not have caused it. I find it a little odd as I have never had a misfire and as soon as I get it back its throwing codes. Funny thing is I gave the dealer new felpro upper and lower intact gaskets to install as well.

Can you please verify that your p0306 was caused by the bad intake gasket ??

Thanks.
 

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I was 100% upper intake gasket as I removed the intake i came to find out that half of it was suck in. replaced it haven’t had a problem since
 

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Brutus
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I was 100% upper intake gasket as I removed the intake i came to find out that half of it was suck in. replaced it haven’t had a problem since
Cool.. Funny thing was I gave the shop a new gasket to install, I'm sure now I have to check to see if they didn't pinch the gasket or something causing my misfire now.
 

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Alternatively, take a can of carburetor cleaner and spray it around the base of the intake manifold while the vehicle is running. Oftentimes, if a gasket leak is present the vehicle's revolutions per minute will surge when the cleaner is pulled into the intake.
 

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Also check for vacuum leaks.
 
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