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Discussion Starter #1 (Edited)
Good evening all. I have an 09 G8GT that only has solo axle backs. When i bought the car it had a missfire when stopped at a light. Especially after running down the interstate. I have taken to dealership multiple times but am told there's nothing wrong. I know these engines have a slight shake at idle its the nature of the beast but this missfire is much worse. I hooked a scan tool to it and had the lead-footed wife drive. Running down the interstate all was good, merge off and stop at light missfire counter started to go up dramaticlly as you could feel in the car shake then it smooths out to the normal idle.

I have replaced the spark plugs with NGK BPR6EFS gapped at .040 and wires. The car has had the cam and lifters replaced under warranty due to the lovely AFM lifters bleeding down.

Anyone have ideas to share?
 

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Maybe injectors need a cleaning? Run some good injector cleaner through the gas tank. Can't hurt trying it.

Might also try cleaning the MAF with the special spray MAF cleaner.

Doesn't the scanner say which cylinders are misfiring?
 

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Discussion Starter #3
I tried the chevron techron (black bottle) in the tank and took a long drive down the interstate no difference I've also cleaned the MAF.

The scan tool showed misfire counts on all cylinders.

Wasn't there a TSB released for the cam or crank sensor connection that caused missfires?
 

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I would check the cam position sensor.
 

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Go back in the scanner and see what cyls. misfire more than others, it will always read on most if not all on residual misfires.the trick is to identify the couple with the most misfires,also look at the fuel trims on both banks,if one bank is adding fuel and misfires on most on that side,you may have contaminated fuel or water in that side of the fuel rail.Remember these have non fuel returns to the tank,so whatever gets in the fuel rail,stays.try that first and let us know
 

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Discussion Starter #8
Yes, on second replacement engine. Original engine had bad cam bearings, replaced with built LS3 that lasted 6400 miles and failed thrust bearing, iron block 408 on engine stand now awaiting installation.
 
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