Misfire p0300 possibly resolved gas 4 weeks pregnant


I was driving my truck down the highway today and after I punched it to accelerate around a car to take my exit I noticed that my check engine light was flashing. Knowing that the flashing check engine light means stop and since I was taking that exit anyhow I exited and turned off my radio so I could hear how the truck was running. Everything sounded fine and the light went out. I kept driving to the store that I was going to and on the way home I punched it again to see what happens. Again radio off from 55 to 70+ and the check engine light starts to flash. I got off the gas and it flashed for 5 sec shell gas credit card 5 and went out. The DIC was displaying no message. When I got home I connected my scan tool to see what what was stored. Under pending codes it reported P0300 Missfire Multiple Cylinders. I then started the truck and when though the computer to look at the data that has been logged. Here is what I found:

I bought it used in Jan. It has 62xxx miles. 2003 Z71. No Aftermarket Alarm. Everything stock except the KN Filter. I did just do my first oil change on the truck and used Mobile 1 5w-30. I don’t know what it had before but I would think dino oil. This oil change was a little over 3 weeks ago but this oil change was done electricity physics khan academy right before I left for Japan. So the truck has been sitting in my driveway for the most of that time. I did tell my wife to drive it every now and then. I think she drove it about 3 times when I was gone on short trips to the store and what not. Also she drove it to work the day I came back so she could pick me and all my luggage up in the truck that has more room than the Audi and she reported no issues. This didn’t surprise me as it only seems to happen at WOT. It currently has 1/4 tank of fuel.

I was thinking that it might be fuel as it has been sitting. But I would think gas pain in shoulder it would take longer than 3 weeks for gas to go bad. I also read that contaminated fuel can cause this code but the primary cylinder that will have a missfire is Cylinder 7 and then 2 and 8. It was explained that these cylinders suffer from this because of how the fuel rail works. I do show misfires on 2 and 8 but 6 is my biggest offender not 7. So I’m not sure this is my problem. Another mention was injectors. I’m not sure about that though. As the light goes out I might keep an eye on it and see what happens after I refuel. I’m not going to clear the codes just yet in the event that gas quality I’m off to the dealer. It’s a good thing that I insisted that the dealer included a drivetrain warranty because of the miles on the truck.

This was my thought exacly. What is over oiled??? It’s not very clear. Maybe I should post a question in the intake mods section. There are plenty of people running the KN filters. I would also think that the initial oil applied by the factory would be correct. They would be wasting money by over oiling them. Again I don’t really think this is the cause of my problem. It is just one of the known issues that I came across that could be the cause. I still have my OEM paper filter that I could drop in to see if there is any change.

Also in the latest TechLink (May gsa 2016 05) that you posted the 5th item states a problem with the Upper Manifold Gasket Leak it would cause a P0300 to set. This is where I really think the problem is. This would make the most sence as far as what I’m seeing. The vacuume created at high RPM could cause enough of a leak to cause my issue. It states that this applies to the 5.3L L59 (E85 capable), as well as the other Gen electricity 4th grade powerpoint 3 and Gen 4 engines. I know I don’t have the L59 but I would think we have either the Gen 3 or Gen 4 engines. I’m not sure what years were Gen 3 Gen 4.

As a side note does the 03 AV use a fuel pressure regulator. If so is it for the entire system or does each bank have it’s own? I know they are totally different powerplants but the 4.3l has a fuel pressure regulator that is known to fail and cause a random missfire. I know this as my Blazer had this problem grade 6 electricity experiments. If I remember correctly this caused the engine to run too rich. I’m not seeing a too rich condition in any of my OBDII values so I’m thinking it’s not this.

Well I had to fly to Louisville on a business trip so I dropped off the AV at the dealer and had them take a look at this as I am covered under a Drive Train Extended Warranty. I called and made an appt for today and had dropped the truck off over the weekend. I had to pull the Blazer back out and drive that. Wow I got spoiled in the AV. Anyhow, the dealer called and left me a voicemail to call them when I was on the flight to Louisville. Once I got settled here I gave them a ring and here is what they said…

1. Misfire has been caused by a blocked Cat. He stated that even though the truck is over 36,000 miles (62,xxx miles) this will be coved under the 8 year what ever mile warranty I think he said 80,000 miles. Anyhow what ever the year/mileage warranty on emissions is. I had printed out a laundry list of TSBs and detailed descriptions gas variables pogil extension questions as to what it was doing to help the mechanic diag this quickly. I also listed some of the more common TSBs that refered to a P0300 code and why they didn’t apply in this situation to help eliminate a few possibilities.