Okay so at the title says its a 5.4L '00 F150 with around 230k miles. The truck is in great shape and for the most part runs good... I towed a car with it from FL to Kansas recently without issue - BUT it has some problems that I need to fix.

Tonight it threw a P0300 code on me after shuddering on the highway at around 50mph.

Now I know what sort of things can cause this code, but let me give you some other details that may help you guys narrow it down because I sure as hell can't.

- replaced all COPs and plugs with motorcraft about 10k miles ago after getting misfire codes for cyl 3,6, and one other..

- Replaced fuel filter about 6k miles ago

- Sometimes when I turn the key in the ignition to start the truck it will crank but won't start untill I let go and then turn it again a second time, then it fires right up.. (someone told me this is a fuel pump issue?)

- I've had a BAD rattling on the driver side that I narrowed down to the cat, recently this rattling has almost gone away completely and I'm thinking maybe it clogged the cat?

- A few weeks ago i went to pass a car on the highway and the truck would not downshift or rev over 4-5k ... but this happened only once and the only sign I notice of a clogged cat.. it otherwise feels strong as usual.

So basically I'm at a point where I don't know where to look or what to try to help me pin down some of these issues... any input would be great.

 

You are trying to include to many other items causing you confusion.
Go with the code 300 first.
Random missfire.
Do not assume that any previous repairs have no issues.
Look for low fuel pressure, low fuel level,
defective EGR valve, cam position sensor, crank position sensor plug, vacuum leak in the intake tract, water in the fuel, plug up connectors etc.
Anything that would affect all cylinders such as the fuel system.
Clear this issue first then address what is left, otherwise you will just go round and round.
Good luck.

 

I agree with bluegrass you are making it to complicated for yourself sometimes the simple thing or even the sure things arent what they seem and can give you bigger problems than you realize i would check your plugs again because if it is a cloged cat like you suspect you may have carbon buildup on your plugs on that side of the block or the other for that matter it wouldnt suprise me seeing how many miles you have on it. and i would also consider getting your fuel pump tested because if someone else bothered to bring it up its worth checking.

 

Well I am leaning away from a fuel issue... I plugged my diablo predator up to it in diagnostic mode and have been watching the fuel pressure and everything seems to be alright, always stays around 40psi.

 

What's the pump sound like -koeo ? Do you hear it charge the lines ? Any deflection going on ? Yea, rule out all possible fuel issues first. I would start by replacing the filter - even though you did it recently. I change mine every 6k , but it isn't required. I think they say to change it every 15k.

Also, check the pressure at the rail vrs the tuner.

If all checks out - Sounds like it got wet.

The rattle - Ford has a TSB about cat shield rattle. The TSB states to use band clamps and wrap them (6 -7" clamps).

 

Do not be mislead by pressure. If the volume is not there you still have fuel issues.

Also when it has to be started a second time do the gauges sweep on the first try?

 

Never paid attention to that... will look next time I have that issue.

 

When you reset the codes by disconnecting the battery the PCM sweeps the gauges. If the gauges sweep when you start the engine the power to the PCM was interrupted. That would give me a clue as to where to look.

Regards

Jean Marc Chartier