So I keep getting a P0300 Engine Misfire Detected. I replaced all the plugs and coils with original AC Delco ones. I'm also getting a P0455 Gross EVAP Leak but I believe that was fixed by replacing the purge solenoid. Now when I removed the air cleaner resonator to replace the plugs and coils I noticed that the PCV hose was cracked and split so that has been replaced. So after all that I hooked up my handy Tech 2 to look at the misfire data. It's mostly #2 that is misfiring but all of them misfire at some point but it only misfires when idling. I drove down the road and the engine was at 2000 RPMs and it didn't hiccup but as soon as I stopped at a light it's misfiring. What else could be causing it?

 

P0300 + P0455=

 

A rusty fuel pump is the answer?

 

When rusted through! Do you have a gas/fume odor? Check the top of the FPM.

 

I checked and it shows a little sign of wear but not much. I'm not smelling any gas fumes at all when running. Even if that was the problem why would it only occur at idle?