Alright so I have my 4.8L running and every now and again it gives a flashing SES light which is P0303 "Random Multiple Engine Cylinder Misfire" and the possible causes of this code are: Bad spark plug wires, bad spark plugs, bad coil, leaky injector, and vacuum leak. Now the spark plugs and wires are all new, I checked all the coils and they are fine, can't find anything wrong with any of the vacuum lines, and the injectors looked good when I looked at them last.

I can be just driving right down the highway no problem running in overdrive, and then all of a sudden the transmission pops out of overdrive and then the SES light starts to flash again and continues to do so for about a minute or so and then goes away. After a few minutes of running in 4th on the highway, the transmission will magically go back into overdrive when it does this. I don't understand why, my only guess is that the engine thinks that something is wrong that the engine is misfiring and thus it thinks that its running on decreased engine power and takes the transmission out of overdrive because of the decreased power.

All I can think else to do is to replace the O2 sensors and maybe the knock sensors, but other than that I have no idea what its doing or even why its doing it....

Does anyone have any ideas?

EDIT: Sorry typed P0303, its really P0300 so it doesn't even know what cylinder is misfiring...

 

Any ideas?...

 

You will need a good scanner to look at the misfire graph and that will tell you what cylinder is misfiring.