I have been working on my father's 2000 F150 5.4L for months and have yet to solve this problem. Maybe someone here can shed some light on what is going on. The truck has a cylinder 1 misfire and has an EXTREMELY rough idle after a cold soak of a couple days. Sometimes this will throw a MIL, sometimes not. The code given every time is P0301 with no other codes in memory. I have the Ford Factory Service Manual to verify specs are within tolerance. To trouble shoot this problem I have done the following:

1. Replaced 8 spark plugs with motorcraft plugs. Code P0301C reappears.
2. Swapped coils between #1 and #3. Code P0301C reappears.
3. Swapped injectors between #1 and #5. Code P0301C reappears.
4. Compression checked all cylinders. All are within factory specs and within 3% of each other.
5. Tested fuel pressure. Within factory specification, replaced fuel filter anyway. Code P0301C reappears.
6. Tested the EGR valve, no issues found but replaced it anyway. Code P0301C reappears.
7. Checked MAF sensor, within factory specs.
8. No long-term loss of coolant and after 8 hours of pressure testing no loss of pressure detected. Leads me to believe the head gasket is fine.
9. Shoved a borescope down the plug hole of Cylinder 1. No issues seen, everything looks normal for an engine with 115K on it.

I'm at a loss here. Is it possible the OBD is telling me it is cylinder 1 when it could be a different cylinder? Or is it possible the Crankshaft position sensor is giving a false reading? Or is this possibly a valve issue? I don't see any codes indicating a problem with another system which is making me wonder where the ghost is inside this machine. Any ideas would be greatly appreciated.

I have attached a FORScan graphic showing the problem. the green line 2nd from the top labeled "NM" is the number of misfires detected.

 

I think it may be an electrical issue to either the injector or coil. However, could it be a sticky valve that is working properly when you do the compression test?

The rough idle after a cold soak could possibly be dirty or sticky injectors - I'd throw some Techron in the gas and see if that helps. However, it could be related to a wiring issue to coils or injectors too.

 

We ran three tanks of injector-cleaner-heavy fuel through, two were Seafoam and one was Techron, clearing the MIL each time and it kept coming back as P0301C. That was the last thing I did was move the injector from #1 to #5. The MIL came back P0301.

Is it possible I am dealing with a misidentified cylinder misfire? That perhaps the miss is coming from a cylinder other than #1?

 

No, I think there is something wrong with the control to either the injector or coil. They are both electronically triggered.

This test equipment may help:


This will test both the coils and the injectors to see if they are firing.

 

I attempted to rule out the coil by swapping coils between cylinders #1 and #2 and the problem kept coming back in cylinder #1. I placed a multimeter on both the coil and injector and set it to measure the frequency of each. Both gave regular results with very little variance in frequency. But I will try ordering that test set and see if I can isolate the issue. If you are confident the problem lies with cylinder #1 I will keep hunting there.

 

OBD2 won't lie. If it says there is a miss in cylinder #1, it's missing. You can confirm with a scanner using real time data.

 

Leave engin running and unplug the number one injector and see if it bogs the engine down in a little bit

 

I have found that this usually occurs after an oil change. They always seen to spill a little and it goes down into the gap around the plug causing the missfire. My E250 van, F150 pickup and the neighbors Crown Vic all had this after the oild change. Took the van to Ford and they wanted to charge me $450 for diagnosis and they could fix. Waved them off took it home and pulled the plug. In doing so, found the bottom of the plug drenched in oil. It was the first thing I checked on the rest.

 

After over 4 years I assume the issue is fixed or the person got rid of the truck. No way to know because this person never reported back.