Code P0300

My P0300 code came back. I’m starting to think it’s a fuel problem. Because the wires, coils and spark plugs were changed about 5k miles ago. And the injectors were changed about 30k miles ago. The only thing that I notice is that it has a rough idle 5-20 seconds after a cold start. If it was warmed up before and then I go drive it, it doesn’t do it. Oh and the fuel filter was changed about 30k miles ago also. Does anyone know what cause it just to have a roughy cold start. Thank you for any help guys!

 

This code indicates multiple cylinders are misfiring. How did you determine it was the 300 code as opposed the actual cylinder misfire codes like P0301 or P0302, etc? Do you have a code reader? One that will show pending codes and clear them?

 

Speaking from experience here in regard to the 300 code and rough idle immediately at startup then going away until the next cold start. Head gasket could be on it's way out and letting a small amount of coolant into the cylinders. Keep a careful eye on your coolant levels. Check the plugs right after another rough start. I chased my tail going through the fuel system, intake system, ignition system, at the bottom of the list was head gasket. Could be a number of things though! Have fun.

 

What parts were used for the coils/wires/plugs?

 

Should I do a compression test? The light has been going on and off for a year now. And when I change the plugs out the rough idle goes away for awhile. And the 1st time I changed the plugs, the cylinder 3 blue has some rust in the threads.

 

This ^^^
This is what happened to me just over a year ago. Coolant leaking into the cylinders due to either the head gasket or cracked head. So watch your coolant levels like a hawk. I did the head gasket job my self and installed two new heads which solved the problem.

 

Compression test/ leak down test/ block test wouldn’t hurt to do. Just beware, I did both a compression test and the block test which both came back with good results but it still ended up being the HG or the heads.
I think someone else could probably explain why that was better than me.

 

Well I just pulled my plugs and my cylinder 3 spark plug has some rust n the threads but doesn’t smell like anything. But I don’t see any moisture in the cylinder.