LS3 Random Misfire
 

Have an 08 LS3 A6 with 14,000 miles that is throwing a random misfire code. It only does it at 100% throttle anywhere between 75-100+ mph. Seems to be on cyl 1 more so than any others. Switched plugs, wires, injectors around with other cyl's and still have the exact same problem. Any ideas? Not to often but it will finally throw a 0420 code. Never had the problem all year. It sat for over a month without being run and now have the problem out of the blue. Dumped injector cleaner in the tank also.

Valve spring, push-rod, compression???? The ONLY thing left. Tough one. If you have access to tuning software, do a cylinder balance test and see if that shows anything.

BC

Did the battery die or was it disconnected while sitting?

Also if its throwing a 420, Catalytic Converters are covered by federal 8yr 80k, have it replaced...

If it was something bent wouldnt it do it all the time, not just under full throttle. I can ease into throttle all the way up to redline and not have the problem, it is just under full throttle at high speeds. Just basically does it under alot of load.

A blocked cat can cause miss fires under load.

Can this damage a motor ??

:cheers:
DH

Yes

Hello,

Replace the coil pack on that cylinder, sometimes they go intermittent.

Douglas in Green Bay :D