Looking at this car for someone else and it has these two codes. I know the p300 is for multiple cylinder misfires and the p1174 is a fuel trim balance issue. Car has new Delco iridium plugs in it. Car runs fine going down the road with good power and it doesn't feel like it's missing.
When you come to a stop, the car will start running real rough and the CEL starts flashing showing it's misfiring. You can also watch the misfires on my scanner. It shows thousands of misfires in cylinders 2 and 3 and about 260 in cylinder 1 and none in cylinder 4.
When the car is idling and running rough, the pre-cat o2 sensor will only switch back and forth in the 700-800 range. When you give it gas and rev it up, it will switch back and forth normally from the top of the range to the bottom.
Does anyone know what else I should be looking at or has anyone had these codes before and got them fixed? Thanks.
Wayne
When you come to a stop, the car will start running real rough and the CEL starts flashing showing it's misfiring. You can also watch the misfires on my scanner. It shows thousands of misfires in cylinders 2 and 3 and about 260 in cylinder 1 and none in cylinder 4.
When the car is idling and running rough, the pre-cat o2 sensor will only switch back and forth in the 700-800 range. When you give it gas and rev it up, it will switch back and forth normally from the top of the range to the bottom.
Does anyone know what else I should be looking at or has anyone had these codes before and got them fixed? Thanks.
Wayne