2001 4.6 65k

It idles fine and cruises fine, for the most part. It's only under torque that I feel it. It's the same stumble I felt when I had an EGR sensor code. Replaced it and all was fine. So I unplugged the new sensor, which is only two months old and it ran fine for several miles then the ses light came on of course and the stumble returned. I changed that sensor again under warranty and cleared the ses but didn't fix the problem. Last year when I had this problem I thought it was the tranny slipping so I did a drain and filter which did not fix it. that was before knowing it was the egr sensor.
So I have an engine problem and no ses light, so far, to give me any clue.

thoughts?

 

Crosspost.

https://www.f150online.com/forums/v8...stumbling.html

 

jd, you likely have one bad coil.
Not what you are trying to work with.
A coil with lowered output will missfire that cylinder under certain driving conditions and still not set a code because it's not a hard fault.
Good luck.

 

good luck as in, good luck figuring out which one it is? thanks! lol
I replaced a coil a few years ago. Pretty sure the ses light came on and it gave me a code to tell me which cylinder it was.

 

Low grade misfires don't necessarily set codes.

 

You have three choices, replace all with known good coils, buy one new and keep moving it and test drive or a dealer stress test to pick out the coil/s..
lol. Good luck.

 

i only drive this truck on weekends usually. after sitting for a week it's running fine. can a failing coil go in and out?

 

Yes it can.
For example, a coil that is heat sensitive with a shorted turns condition expands and contracts internally from engine bay heat vairations and aging.
The wire is fine 'enamel' covered and wound on each other per turn on a bobbin form and magnetic materal core.
If the enamel wears through, shorted turns results.
You cannot pick this up with a meter test because the change in DC resistance is too small to measure with a normal meter and it's accuracy unless you knew what 'that coil' measured as good and what it measures in fault with a sensitive bridge type test set. However the effect on the magnetic flux around the core it's wound on is to lower the total voltage output by reducing the the flux across 'all' of the total turns on the core.
The other extreme result is wire breakage at one of the terminals internally but that is a hard fault and sets a code to ID the cylinder.
The shorted turn condition "is" detected by the computer when it happens by measureing the crank rotation time of that and all cylinder, compairs it to the normal average of all the rest of the cylinders and stores it in a temporary memory as a fault count.
** by the way, this is how the computer self adjusts as the engine ages and cylinder pressure begin to drop/vary by re-adjusting the "average readings" in the compare table for each cylinder.***
Pretty clever software!
If the coil clears the condition, the count is cancelled and no code is set if the count stays under a certain total, (per occurance).
This condition can repeat on a drive cycle basis or whenever the conditions are present.
I have trapped this type of fault on a real time basis a number of times with a good scanner and IDed the cylinder everytime.
With a monitor on board you can see the radical retard in ignition timing that happens when a coil can't fire a cylinder. This adds to the 'intensity' of the way it feels when missfire occurrs.
If you have a good spare coil and tools it can be changed along the road if you get stuck especially if towing and the power drops too much.
There you have it, the mechanics of the fault to help understand what happens.
Only here will you get this info in related depth.
Good luck.

 

I think it's the fuel pump guys. Today the truck just died on me. Felt like running out of gas. putting some gas right into the throttle body would fire up just while that burned. I had forgotten I suspected a fuel pump problem months ago. After installing a new alternator and battery, for another issue, the fuel pump problem seemed to go away as well. I banged on the tank with a hammer and it started right up, but, I have that skip in the engine back. Could a bad fuel pump starve the engine causing what feels like the engine skipping?

 

If you are thinking it is fuel related, it might also be your FPDM Fuel Pump Driver Module. It is up in the spare wheel recess. These seem to corrode and fail. Had mine do it where it worked intermittently and finally died. Easy replace if your spare tire come down easily.

https://www.f150online.com/forums/v8...er-module.html

 

2001's don't have a FPDM, it's a constant pressure return system.

When was the last time you changed the fuel filter?

 

fuel filter is less than 3 years old, which for me is about 3k miles for this truck.
again, banging on the tank, the truck fired right up so i'm really thinking the pump.\
would explain the skipping under torque if the engine is starving for lack of pressure.
i've never dropped a tank to change one out.

 

Well that certainly rules that out then LOL

 

I just let a local mech. change my bad one. Coils were $45 at the parts store plus I still had to figure out which one it was then change that one...

little over $100 & one day at the stop and she's back to running good now. Glad I just let them deal with it. Will most likely be going back there next year after tax returns come in, to get all new plugs/coils & whatever else she might need. Just hope this 1 can get me by till then.