P0304 is driving me nuts!
P0304 is driving me nuts! Its a 2014 5.3L (Gen 4 not Gen 5) that I just bought with 150K on it with a Cyl #4 misfire. I swapped coils, new spark plug and wire on that cyl and no change. It still has AFM and I am using a Range style disabler (I know its not really a fox)
When it was idling, I can smell raw fuel and it had a little white smoke, but smelled no coolant or oil. I looked and noticed the air filter was FILTHY and the MAF wire inside was black. I pulled it and cleaned it, put a new air filter in. Still smells a little like raw fuel but not as bad. I'm guessing the #4 lifter is bad and thats why the code is there. The odd thing is, when you rev it up, the idle hangs bad. It goes to 3K RPM and when you let off, it takes a good 3-4 seconds to come back down to idle RPM. I changed the oil filter and added a quart of Marvel mystery oil.
Today I ran a compression test with the plugs removed from 2 and 4. Both of those came back at around 166-168. After compression test, I observed the intake and exhaust rockers while cranking and both are opening and closing like normal. I swapped to a known good flex fuel injector and deleted the P0304. I started it and it seems better and no CEL currently but still idles rough and has a miss and smokes pretty bad. I decided to drive it around the neighborhood and it smogged the streets out. It now smells almost like burning oil/burnt clutch (Its an automatic) but that smell might be the Marvel mystery oil burning so I am lost.
When it was idling, I can smell raw fuel and it had a little white smoke, but smelled no coolant or oil. I looked and noticed the air filter was FILTHY and the MAF wire inside was black. I pulled it and cleaned it, put a new air filter in. Still smells a little like raw fuel but not as bad. I'm guessing the #4 lifter is bad and thats why the code is there. The odd thing is, when you rev it up, the idle hangs bad. It goes to 3K RPM and when you let off, it takes a good 3-4 seconds to come back down to idle RPM. I changed the oil filter and added a quart of Marvel mystery oil.
Today I ran a compression test with the plugs removed from 2 and 4. Both of those came back at around 166-168. After compression test, I observed the intake and exhaust rockers while cranking and both are opening and closing like normal. I swapped to a known good flex fuel injector and deleted the P0304. I started it and it seems better and no CEL currently but still idles rough and has a miss and smokes pretty bad. I decided to drive it around the neighborhood and it smogged the streets out. It now smells almost like burning oil/burnt clutch (Its an automatic) but that smell might be the Marvel mystery oil burning so I am lost.
If you have a misfire, the o2 sensor reads the unburned oxygen and the pcm corrects by dumping fuel into that bank. Without a way to do any live scanning, it is a shot in the dark, but try swapping injectors and see if the problem follows the injector. That will at least eliminate one more potential suspect.
