P300 Random Misfire

[Timmah108]

Hi All,

Hoping someone here may have an answer for me. Basically what is happening is when I start my s80 I have a solid CEL and when my RPMs is over 2000 I receive a flashing CEL. The only ODB II Code I get is the P300. I have changed all my spark plugs and ignition coils with no change.

It all started when my Harmonic Balancer broke and I needed to replace it. Once I got the car back from the mechanic after driving it for half a block the CEL came up.

What else can I check to try to resolve this issue? Any ideas what can be causing it?

Thanks,
Tim