I decided to check the condition of my spark plugs today, (96,000 miles) and took out #5 and #6 plugs and they looked great. Very clean.

I put them back in, made sure the coil packs were well seated and upon startup, a very bad misfire occurs.

Took it to Autozone for a OBDII scan and came back with thee codes:

P0300
P0301
P0302
P0303
P0304
P0305
P0306
P050b

Any idea what would cause a misfire code on all cylinders?

 

An update:

I disconnected the wiring from the coil packs on #5 and #6, and the engine runs the same. So I guess both cylinders are not firing.

2008 XC90 3.2

 

It turned out that I was numbering the cylinders wrong, it was #1 and #2 cylinders, not #5 and #6. Anyway, I had the coil pack wires crossed and that was the problem.

 

damn if i wouldve seen this post earlier i couldve told you what that problem was in the first post. ive taken those engines apart many many times and the coils get switched because of the way they route.

 

damien360

I wish you would have seen it earlier too. It was a depressing few hours until I figured it out. You are right about the wiring route, I could have sworn on a Bible I had them on right because of the way the wires had taken a set. Live and learn. Thanks