I have a 2001 chevy silverado 3500 6L gasoline engine. I have been getting a P0307 random multiple misfire #7 on and off for a few months now, occasionally the P0300. Check engine light comes on when I am going up hills, often under heavy load and sometimes when the truck is cold in the morning and the truck starts to run rough until the code clears, which it does pretty quickly usually. I have replaced coil, crank sensor, cam sensor, fuel injectors. Can't figure out what is causing this problem. If I unplug the battery over night the code will be cleared and the truck will be running just fine the next day.

Any suggestions would be appreciated.

Anything in the ign system can also cause this a full scan under the misfire conditions will point to which cylinder actually shows the miss use misfire counts.. wires, plugs are the usual suspects. I have had coil wires fail on these engine this can cause 0300, not usually one cylinder. Make sure you have proper fuel pressure also, 58-62 psi.

Check for vacuum leaks and around the intake gasket area too.The 6.0s including the 4.8 and 5.3s do have problems with intake gaskets which are made out of plastic.They blow out and sucking in air causing a miss.Spray cab cleaner around the intake gasket area and if you notice a change,they are bad