po300 is a multi missfire code, so you are runnign too rich foiling out the plugs.

 

Upadate on my P0300 woes.

The light came back on. I compression tested and I wouldnt say it passed with flying colors but it's in spec. 143, 150, 155, 145 warm - I'm a little concerned about the variance as it's not supposed to be more than 15 and mine are at 12. I then took it to the dealer and they did a full top engine clean and injector clean service because my fuel trims were fluctuating quite a bit and when they would get too far out the car would get a P0303. The issue finally got to where they could get it to trigger the code in their service bay.

I picked up my car on Monday from the dealer, they finally replaced all 4 injectors. The car is idling smoother and appears to be running better as well. The mechanic told me he has never had to replace a faulty injector but he's run accross lots of dirty ones but he thought mine looked great. No P030x as of yet (4 days and counting, the longest in a long time). Crossing my fingers. I've noticed that my A/F ratios are much more consistant especially at idle (this is where the P030x error normally occurs). They used to wander out as lean as 15.6 and now they are 14.9 - 15.0 at idle and hold steady at 14.7 cruising. I've noticed my fuel trims dont stay at 100 in evoscan though so they are still fluctuating some, especially if it's raining and I am in traffic (Accessories running, fan, headlights, wipers etc), this seems to aggravate the P030x issue for some reason.