I have a 2002 Ford F-150 with a 5.4 Triton. 212,xxx miles. I replaced the cops and the plugs about 6 months ago. I was pulling a trailer up hill last week and the engine was under a load doing about 3000rpm. It began to misfire and give me a flashing mil. However, before I went very far the engine began to run fine. It happened 3-4 different times. Hoewever, there is no code recorded. I've driven the truck nearly 100 miles with no problems, but I'm going to be pulling that trailer uphill again next week. Any suggestions?

 

Fuel pressure could be low due to a worn fuel pump. Low fuel pressure is most notable under a load such as when accelerating, hill climbing, or towing.

 

A flashing CEL tells you that fuel was being passed through to possibly melt the cats in that bank or banks from lack of ignition.
So lack of fuel would not be the problem.
Under load at 3000 rpm and outright misfire that apparently is intermittent.
If the misfire clears long enough the code and CEL would be cancelled.
A way to find which cylinder was the cause is to look at mode 6, test 53 witt a Scanner.
At that location is the misfire record for all 8 cylinders.
This memory does not have an ability to set a code and is not cleared any way but with a power down of the PCM.
One or more should have high counts as the suspect.
It could be the coil, the boot, the connector a plug or even a Cat already causing blockage along with the cylinder misfire.
After all at 3000 on a hill under load, there is less air flowing in the engine bay do to the lower road speed and higher heat produced by the engine.
Good luck.

 

My first guess would be along the lines of alloro's.

A flashing CEL indicates a Class A misfire. PCM doesn't know if it's from a secondary ignition break down or from a lack of fuel or from lack of compression.
It just picks up on rotational delays.

Has the fuel filter ever been changed?

Was the fuel level low when going up this hill?

Is it the original fuel pump?

Why were the COPs and plugs changed 6 months ago.

Might want to tape a fuel pressure gauge to the windshield to check pressure under load.

Otherwise, follow bluegrass's lead for identifying which cylinder is misfiring.

 

The fuel filter was changed about a year ago, but the fuel pump has never been changed. There was probably 3/4 of a tank of fuel at the time of the misfires.

The COPs were changed because I had two go bad inside of 6 weeks and since they all had more than 200k on them I figured it was time to change them. I changed them all at the same time. While I was doing it I changed all the plugs.

I have a scanner but I don't think it does mode 6. I'll chase this with someone who has one. Thanks for the input.

 

Does anyone know where I will find someone who will run a mode 6 scan on my truck without charging me and arm and a leg to do it? I have tried a couple of places but none of them have a scanner capable of running that test. I have a great scanner that I love, but it will not do a mode 6 detailed scan for misfire data.

 

Not that this will help you much but on page 9 of the OBDII overview, third paragraph under misfire algorithm describes the conditions that will cause the CEL to flash.
Its a loss of ignition not fuel the first time around.
There is a condition that will shut off the injector if the issue is detected a second time to try and prevent melting the cat if it is not already melted by repeatedly driving the truck with the fault..
I have long ago had experience with this kind of fault.
Finding a source with a Scanner to look at this misfire is likely more about not knowing how because they are not competent to go that far in diagnostics.
Good luck.

 

...Great Question....Who make a scanner that has mode 6 ability, thats reasonably priced?

 

https://play.google.com/store/apps/d...l.torque&hl=en

https://torque-bhp.com/wiki/Bluetooth_Adapters