Recently my truck has been sitting a lot more than normal and the other day i jumped in it to head to a buddys house when the check engine light came on. P0300 random and multiple misfires. as well as p0455 large evap leak. well ive tried everyhting i can think of and still no luck fixing this problem. Runs righ at idle and as soo as you rev up engine like starts flashing. Any help would be appreciated

 

the large evap leak has nothing to do with the misfire condition so ignore it for now.


even though random misfires dtc are set, if you have access to a scan tool with misfire data...view the data to see which cylinders are misfiring.


misfiring at high rpm can be from:
-bad coils, plugs, plug wires
-low fuel pressure
-exhaust restriction/clogged cats


I would start by checking fuel pressure.

 

Flashing light indicates misfire, I'd also suggest the same troubleshooting tech 2 is. Find the misfire. Evap codes usually end up being loose gas cap or cracked line.