Ok i have looked and searched and came up with alot of answers but none of them in the posts have ever really been resolved.. So here goes

2002 f150 5.4 130,000 k&n intake and throttle body spacer all 4 cats no muffler always run 91 octane gas and change oil every 2800 miles along with a bottle of lucas injector cleaner

a couple weeks ago i had a miss,buck,shudder it took like 30 miles for the cel to pop on it was cyl #4 misfire pulled the cop and it was covered in water.

The boot had went bad so i changed the coil miss and buck went away.

Well now between 1800 and 2200 rpms my truck is real sluggish and it has the infamous od shake at low highway speeds but mash it on down and it takes off just like it should mpg has decreased from 17-18 to 14-15 city.

About 10,000 miles ago i replaced the plugs went with motorcraft sp479 (factory plugs) and also replaced the fuel pump.

The fuel pump was my fault tho when i fill up i always fill it to the brim lol.

But anyway i had my cats checked by local muffler shop they are good new fuel filter still no resolve

I know that its more than likely a cop problem but is there any way to pinpoint which one it is ? Can you use an ohmmeter and check the resistance ?

Just any help would be appreciated

Thanks Smokey

 

There was just a thread like this. Bluegrass explained the whole deal about how lean the mixture goes when the EGR opens, like that 40 mph OD scenario. The spark has to be optimal or get that buck and shudder under those situations. But you are right, I think what was concluded was to change all of them or change one at a time and do the process of elimination. Problem seems to be it won't toss a CEL unless it continued, but clears up when the RPM's increase. Your not getting a hose drip down into #4 keeping things wet, or a cowl seal, or even the squirter like mine was doing? There must be something a dealership tech. can hook up to pinpoint it...I would think.

I'm just curious, but why does filling the tank to the top ruin the fuel pump?

 

When you (top off ) the tank or round it up to the next dollar it pretty much air locks the system where the return lines in the top of the tank can't breath and that puts the fuel pump in a air tight system causing it to work against itself causing it to fail prematurely that's what the Airtex vendor rep told me anyway. And I'm going to have it scanned by a mechanic friend Thursday and see if he can pinpoint anything. I sold him a genesis scanner a while back for cost so he better hook me up lol.

 

Oh smoky,

Have him use that Scanner in it's trap mode if it has one.
Go out for drive with it connnected.
When the missfire happens it will trap the cylinder causing it by freezing the data.
Now that's not so hard is it?
BTW, 2800 mile oil changes is just burning your money away unless the oil and filter is free.
What you Airtex rep told you is not very good.
The fuel system is indeed a two pipe system but the complex testing the PCM does with the hardware draws a vacuum in the tank testing for leaks thus no air can cause a lock.
Your more apt to soak the Charcoal EVAP filter than create an air situation.
I have topped my tank countless times over 184,000 miles and still have the original fuel pump.
Good luck.