P0306 & P0315 Misfire on 2004 4.6L Triton
06-17-2016, 08:49 PM
#1
P0306 & P0315 Misfire on 2004 4.6L Triton
Hello,
My 2004 F150 (154K miles) started to run rough a few weeks ago. The issue was noticeable at idle and the truck lacked power on acceleration. The CEL light finally came on and I found P0306, later that day it also had a PO315.
I did some research (and a lot of YouTube searches -
) and see that its a misfire on No. 6 cylinder as well as a misfire with the first 1000 rpms at startup.
The obvious candidates came to mind:
I attempted to remove No. 5 to compare it to 6. It creaked and felt like it was going to strip or break, so I tightened it back up. I checked resistance on coil pack 5 & 6 and they were the same. Not wanting to dig deeper due to fear I may strip or break off a plug, I swapped coil pack 5 & 6 and put it all back together. THE ISSUE WENT AWAY COMPLETELY. I cleared the codes, in hoping that if it did come back I would know if it followed the cylinder location or the coil pack. I thought maybe intermittent connection to the injector or coil pack.
A few weeks later, on the interstate (I don't hardly ever drive on them or at those speeds with this truck) the CEL came on again and this time the vibration was much worse. The CEL flashes for a short while before coming on and staying on solid.
Another code check showed the exact same codes.
Since I was concerned about breaking the plugs off I opted to take it to the dealer.
Here is what they did for me:
The only thing they turned up was "Evidence of coolant and oil on plug 6 and 7"
Now I know that if the plug hole is filling with coolant, this CAN short out the plug and cause a misfire. But here is the weird part: I reset the codes at the dealer and started it up. I noticed a slight vibration. The truck accelerates fine (I didn't go faster than 40 mph as I was not on any highways). I have driven over 20 miles today just to see if I can get the CEL to come on and it has not. Although the engine stumbles just a bit, it accelerates normally and no CEL.
What are the forums experience with this? The dealer was amazingly supportive and the adviser seemed to want to help me, but they quoted me about $680 for that repair. I almost got a feeling he was seriously hinting this was the issue, but didn't come right out and say it.
Sorry to be so long winded, but I need to decide what else it may be and if I am going to pay them or tackle this repair myself. I'm alco concerned that it may be something else, such as a stuck valve or something..
Any input is welcome.
My 2004 F150 (154K miles) started to run rough a few weeks ago. The issue was noticeable at idle and the truck lacked power on acceleration. The CEL light finally came on and I found P0306, later that day it also had a PO315.
I did some research (and a lot of YouTube searches -
) and see that its a misfire on No. 6 cylinder as well as a misfire with the first 1000 rpms at startup.The obvious candidates came to mind:
- Spark plugs
- Coil pack
- injector
- Compression
- Voltage or ECU issue
I attempted to remove No. 5 to compare it to 6. It creaked and felt like it was going to strip or break, so I tightened it back up. I checked resistance on coil pack 5 & 6 and they were the same. Not wanting to dig deeper due to fear I may strip or break off a plug, I swapped coil pack 5 & 6 and put it all back together. THE ISSUE WENT AWAY COMPLETELY. I cleared the codes, in hoping that if it did come back I would know if it followed the cylinder location or the coil pack. I thought maybe intermittent connection to the injector or coil pack.
A few weeks later, on the interstate (I don't hardly ever drive on them or at those speeds with this truck) the CEL came on again and this time the vibration was much worse. The CEL flashes for a short while before coming on and staying on solid.
Another code check showed the exact same codes.
Since I was concerned about breaking the plugs off I opted to take it to the dealer.
Here is what they did for me:
- Replaced all 8 plugs (one was broken, but not on no. 6)
- Relative compression test - No loss of coprtession on any cylinder
- Inspect fuel rail and test injector - all was normal
- Checked for proper firing of coils and injector - normal
The only thing they turned up was "Evidence of coolant and oil on plug 6 and 7"
Now I know that if the plug hole is filling with coolant, this CAN short out the plug and cause a misfire. But here is the weird part: I reset the codes at the dealer and started it up. I noticed a slight vibration. The truck accelerates fine (I didn't go faster than 40 mph as I was not on any highways). I have driven over 20 miles today just to see if I can get the CEL to come on and it has not. Although the engine stumbles just a bit, it accelerates normally and no CEL.
What are the forums experience with this? The dealer was amazingly supportive and the adviser seemed to want to help me, but they quoted me about $680 for that repair. I almost got a feeling he was seriously hinting this was the issue, but didn't come right out and say it.
Sorry to be so long winded, but I need to decide what else it may be and if I am going to pay them or tackle this repair myself. I'm alco concerned that it may be something else, such as a stuck valve or something..
Any input is welcome.
