[Solved] P0172 and P0300 at the same time

[AndyA]

Today, out of the blue I had a rough idle, CEL and these two pending error codes:

P0172 = system too rich bank 1
P0300 = random/multiple misfire detected

I probably have the original O2 sensors and I am at 99,500 miles so I have ordered all four (plus the socket, the thread chaser, etc.) as they probably need to be replaced anyway.

Anything else I should be considering if the O2 sensors don't fix it? Could broken pre-cats cause these codes for example?

Thanks, Andy

 

[AndyA]

Solved both codes by replacing the O2 sensors. Andy