First Time Poster - 2009 S5 Misfire(s)
 

Hello,

Just joined the forums today as I'm stuck with my S5.

I have the 4.2l V8 and I am getting a check engine light on occasion. I've been pulling codes and clearing the light for a few months now but I'd like to get to the bottom of this as performance seems to be effected and idle is slightly bumpy.

Almost since I bought it, the car stutters a bit on start. When cold, the idle can be a bit erratic, nothing major but it jumps around a few hundred RPM before settling between 700-800 (on the dashboard, no external gauge).

There is a bit of hesitation on accelaration, and the engine seems to stumble a bit.

I replaced all 8 coilpacks and sparkplugs a few months ago but this made little difference. The car seems to be VERY sensitive to fuel grade.

The codes I've pulled are: P0300, P0301, P0303, P0305, and P0306. I am aware that these are misfires on those cylinders.

Any ideas of what might be wrong given that I've already replaced ignition components? That fact and the sensitivity to poor fuel lead me to believe there is a problem with the fuel system somewhere. Injectors? And what aren't 2,4,7,8 effected?

Thanks in advance for any input.

Cheers,

JB