Misfire problem and fuel pump!
Thread Starter
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Junior Member
Joined: May 2009
Posts: 4
Likes: 0
From: alaska
Misfire problem and fuel pump!
Hello all,
To shorten my story a bit, I had a problem with a #4 misfire on my 2006 F150 5.4 with 136,000 mi on the clock.
I started changing out the plugs, cops,fuel sending unit, and a injector with no avail. As a last ditch effort i decided to replace the fuel pump which did the trick
. My question is why would I get only a #4 misfire? I'm an aircraft mech by trade, it doesn't seem to make much sense why a fuel pump going out only throw a p0304 code and not making the whole damn engine misfire. Thanks in advance for any enlightenment y'all might give me.
To shorten my story a bit, I had a problem with a #4 misfire on my 2006 F150 5.4 with 136,000 mi on the clock.
I started changing out the plugs, cops,fuel sending unit, and a injector with no avail. As a last ditch effort i decided to replace the fuel pump which did the trick. My question is why would I get only a #4 misfire? I'm an aircraft mech by trade, it doesn't seem to make much sense why a fuel pump going out only throw a p0304 code and not making the whole damn engine misfire. Thanks in advance for any enlightenment y'all might give me.
Senior Member
Joined: Jun 2011
Posts: 140
Likes: 1
From: Dallas
This doesn't make much sense. I suspect that you had more than 1 issue as is often the case when your troubleshooting something and it's not making any sense. People always assume there is only 1 issue to be corrected. I troubleshoot for a living everyday and I learned this lesson again and again.
Did you still have the code for misfire on #4 after the COP/Plug/Injector change on that cylinder?
You should have gotten a code from the fuel rail pressure sensor if the pump was bad and as you stated it should have impacted all the cylinders not just #4. On the COP harness connector there is a little rubber seal inside the connector that can get torn and prevent the connector from latching onto the COP completely. I had this same issue on #4 cause a misfire on mine. I had it one and off several times chasing the issue and didn't notice it because it's sofar back there I couldn't tell it wasn't going onto the COP all the way. I suspect your issue will show up again. It's probably a coincidence that it started working after changing the pump. If it shows up again check the rubber seal in the COP connector to make sure it's not torn or already pushed into the bottom of the connector. When I had this problem the misfire would come and go until I found the root cause.
Did you still have the code for misfire on #4 after the COP/Plug/Injector change on that cylinder?
You should have gotten a code from the fuel rail pressure sensor if the pump was bad and as you stated it should have impacted all the cylinders not just #4. On the COP harness connector there is a little rubber seal inside the connector that can get torn and prevent the connector from latching onto the COP completely. I had this same issue on #4 cause a misfire on mine. I had it one and off several times chasing the issue and didn't notice it because it's sofar back there I couldn't tell it wasn't going onto the COP all the way. I suspect your issue will show up again. It's probably a coincidence that it started working after changing the pump. If it shows up again check the rubber seal in the COP connector to make sure it's not torn or already pushed into the bottom of the connector. When I had this problem the misfire would come and go until I found the root cause.
Thread Starter
|
Junior Member
Joined: May 2009
Posts: 4
Likes: 0
From: alaska
This doesn't make much sense. I suspect that you had more than 1 issue as is often the case when your troubleshooting something and it's not making any sense. People always assume there is only 1 issue to be corrected. I troubleshoot for a living everyday and I learned this lesson again and again.
Did you still have the code for misfire on #4 after the COP/Plug/Injector change on that cylinder?
You should have gotten a code from the fuel rail pressure sensor if the pump was bad and as you stated it should have impacted all the cylinders not just #4. On the COP harness connector there is a little rubber seal inside the connector that can get torn and prevent the connector from latching onto the COP completely. I had this same issue on #4 cause a misfire on mine. I had it one and off several times chasing the issue and didn't notice it because it's sofar back there I couldn't tell it wasn't going onto the COP all the way. I suspect your issue will show up again. It's probably a coincidence that it started working after changing the pump. If it shows up again check the rubber seal in the COP connector to make sure it's not torn or already pushed into the bottom of the connector. When I had this problem the misfire would come and go until I found the root cause.
Did you still have the code for misfire on #4 after the COP/Plug/Injector change on that cylinder?
You should have gotten a code from the fuel rail pressure sensor if the pump was bad and as you stated it should have impacted all the cylinders not just #4. On the COP harness connector there is a little rubber seal inside the connector that can get torn and prevent the connector from latching onto the COP completely. I had this same issue on #4 cause a misfire on mine. I had it one and off several times chasing the issue and didn't notice it because it's sofar back there I couldn't tell it wasn't going onto the COP all the way. I suspect your issue will show up again. It's probably a coincidence that it started working after changing the pump. If it shows up again check the rubber seal in the COP connector to make sure it's not torn or already pushed into the bottom of the connector. When I had this problem the misfire would come and go until I found the root cause.
The only code that poped up was the P0304 and yes after i changed the plug, cop and the injector i still got the code. Maybe it was a concidence but my truck is running fine at the present moment... Ill check it out in the morning as a precaution or wait till it gets a little warmer out.