2008' / 3.0L / V-6 engine stumbling/mis

tom thanks for your reply!
Most times hard for me to relay all I need to say here, once again...
Also will try to get the phone logged in today for faster reply, (desktop login only for years now).

K & N permanent filter is kept clean just like the oil, (unrelated tranny fluid change done once also overdue to change with fluid here).

The stumble happens/happened at 55-60 MPH normal cruising RPM around 2000-2200 RPM, (I drove it to get a few groceries on Saturday and it performed perfectly-even the last 2 miles home when I romped on it). Thanks for info on rev limiter-had no idea they would put it into the program.
Fuel pump replaced 3 times, (took OEM to clear the code-2 diff aftermarket failed to communicate with the ECM) last year.

Would I see the fuel pressure output on my code scanner live data?

I'll go over MAF wiring but I keep the underside of the hood pretty clean, (fanatical about that-other than lower engine oil leak).
And I'll check the PCV valve.

Will have to budget 5 more coils, (I have the new plugs) before I go through the task of pulling the upper intake to change the plugs.
Not gonna pull the intake for plugs now-leaving the original 154K mile coils there to give me issues in the near future, (and I've also had the new upper intake gasket/O-rings for that job for a while now).

Thanks again.

When you do pull the upper intake, I suggest disconnecting the throttle body from the intake(4 bolts) and moving it out of the way rather than draining the coolant and disconnecting the coolant from the throttle body. You have just as good access and don't have to drain/refill/spill the coolant. All the assemblies on the rear of the intake can be disconnected and 'left standing' by them self for the most part. IOW, they do not need special support nor to be removed completely.
I am not a fan of K&N filters as keeping them cleaned and properly oiled seems to be an 'art' that I do not claim to have. There is also a good possibility the oil can form a film on the MAF heated wires, causing mis-read of the actual airflow. The heated elements need to be perfectly clean and a little oil in the airflow is not a good recipe. Your choice.
Worn plugs can give stumble and hesitation and 'trailer hitching' when driving and would be most noted on acceleration up a slight hill where you do not get a shiftdown, but are working the engine harder than on flat ground, cruising. The plug breaks down(phrase) and misfires as the spark cannot cross the gap when the cylinder pressure is highest(under load, working hard...). Replacing worn plugs restores the spark ability to jump the gap successfully.
tom

"tomw,
When you do pull the upper intake, I suggest disconnecting the throttle body from the intake(4 bolts) and moving it out of the way rather than draining the coolant and disconnecting the coolant from the throttle body. You have just as good access and don't have to drain/refill/spill the coolant. All the assemblies on the rear of the intake can be disconnected and 'left standing' by them self for the most part. IOW, they do not need special support nor to be removed completely.
I am not a fan of K&N filters as keeping them cleaned and properly oiled seems to be an 'art' that I do not claim to have. There is also a good possibility the oil can form a film on the MAF heated wires, causing mis-read of the actual airflow. The heated elements need to be perfectly clean and a little oil in the airflow is not a good recipe. Your choice.
Worn plugs can give stumble and hesitation and 'trailer hitching' when driving and would be most noted on acceleration up a slight hill where you do not get a shiftdown, but are working the engine harder than on flat ground, cruising. The plug breaks down(phrase) and misfires as the spark cannot cross the gap when the cylinder pressure is highest(under load, working hard...). Replacing worn plugs restores the spark ability to jump the gap successfully.
tom

Click to expand...

Tom,
Will I need a gasket to unhook the throttle body, (agreed on unhooking the coolant lines as I could also see it making a bigger mess).
I've always stayed on top of my K & N, (owned several on my airboat and 4 wheelers in the past so it's a given to me to maintain).
So far the oil leak is only on the bottom portion of the engine, (upper and bottom side of hood etc all dry).
Just got the other coils ordered yesterday, (alligator trying to crawl under my fence to get dogs took priority away from me-even though he is only a 4 footer I have an older dog that wouldn't escape him). Coils coming from here in Florida, (I opted for Bosch versus Motorcraft due to budget) so I should see them Tuesday latest to start the upper intake.
The learning curve here, (turned 62 last week) is a necissity though as my plans are to build a Ford powered airboat in the near future, and my engine of choice to run on pump gas will be either the Ecoboost from a Lincoln or a Stang' Coyote that'll silence the Chebby LS powered airboat crowds LOL.

And I have put another 100 or so miles in it, (less than 1/4 tank of fuel trying to run out, (even after putting two bottles of fuel treatment and injector cleaner in it). Yesterday was just as you described "trailer hitching" as it seems it's just under load, (and did it even when I shifted out of OD into drive).
Thanks again for your reply.

I have done the R&R twice, using the same gasket over again. Once for plugs and the second time for cam cover gaskets & plugs. I was just careful removing, and fitting it back to the manifold. I kind of 'feel' how the throttle body sidles up the the intake and move it around until it feels as if it is in its spot, then run in a couple bolts finger tight to hold it in place. So far so good. If the O-ring style gasket has taken a set, and has no spring left to it, hardened, replacement is not a lot of dough. You can also wipe RTV onto the O-ring, no blobs, no daubs, just a 'finger wipe' to 'wet' the surface of the O-ring gasket. The RTV will set after while and more or less adhere to the O-ring and fill any tiny gaps. Some use white lithium on O-ring gaskets for the same purpose. There is zero RTV left to get squished out and be visible anywhere if you keep the application to a minimum. It really is just a wipe. But not absolutely necessary, and I have not used it on this application, nor the cam covers.
If/when you do the job, I would suggest replacing the PCV valve as it is difficult to get to, and likely has not been replaced. I have read that a failred PCV can pull a lot of oil out of the crankcase in short while, at least some report that. OTOH, it could be they thought they checked the oil regularly, and actually did not. I cannot say. I did replace mine. With Motorcraft, theFoMoCo OEM.
tom

I don't know about gas supply in your locale, but historically I do not replace fuel filters on any sort of regular basis. If you have fuel supply problems, the symptoms can vary based upon the problem. Climbing a long hill would place the most demand on a pump, driver and filter to produce enough flow over time to supply the engine. Accelerating as in merging onto a freeway would demand supply right now, but the demand would slack in a short while to cruise speed demand. A failing electronic driver would vary the pressure and delivered volume depending upon electron flow... it could change as quickly as throwing a switch, from normal do decreased flow/pressure.
In a closed fluid system, pressure depends upon restriction. If the fuel can flow freely, it will not develop any pressure. Once flow is restricted, pressure will build quickly, and drop just as quickly if the restriction is removed.
Checking the volume the pump can deliver is in some respects a better test than pressure alone. A pump can build pressure, but fail to deliver enough for an engine to run properly.
tom

Put many hours on it this weekend, (due to Murphy's law). SO FAR TWO OF THE THREE FRONT CYLINDER BANK SPARK PLUGS HAVE STRIPPED THE THREADS JUST REMOVING THE EXISTING PLUGS ARGH!!!
So I started with a 14 mm thread chaser hoping to retap/cleanup the threads enough to get the bugs back in, (parts counter "this is an everyday issue with Ford's Triton engines 16 plugs that Ford got sued over as the "repair plugs" cost $30 each")!
The thread chaser proved worthless as the plugs left no threads as they came out, (confirmed with the horoscope I had to go buy-worth every penny of $89-paid for itself very first day I used it).
So...let's go buy 14 mm heli-coil kits for the plug bores. Threaded my first hole yesterday(after welding a 9 mm metric socket to the tap so I could use a 3/8" extension to turn the tap/he bore too small for a socket to fit over the 9/16" hex head tool). Then Iet the red locktite set up last night to unthread the tool out of the insert, (tool was pulling insert back out as I unscrewed it yesterday). Hopefully an hour from now I'll get the #5 plug back in, (I did not realize yesterday I also needed to weld an extension onto the tool that you Hammer the top of the insert onto flare it out). So maybe by tomorrow I'm actually back to trying to find my engine miss instead of backtracking with the oh crap stuff!
I will go ahead and make sure that I have new heater core inserts for all three back cylinders before I even start that!
Tom I did change the fuel filter and like you said it was not an issue I just knew it was a cheap part I could throw at it to rule that out, I could blow through it easily once I pulled it out. And I did get the tranny fluid changed finally Saturday, (4 hours using the 3.5/7/6 pan drain / front hose drain flush method) as I wanted to make dang sure that this was not a transmission issue, (trying to slip) even though I'm pretty sure it was not the fluid change was overdue and I've had the fluid here for a year.
So I have my fuel pump module driver in route and two more coils I should receive by tomorrow. Hopefully I will finally finish replacing all the coils and plugs tomorrow.

Well, look at it this way. You are not lying in a mud puddle. It is not snowing or raining on you. The floor surface looks dry and almost level, and you can close the doors if the wind comes up.
I have heard that some people use an impact and run spark plugs out of the cylinder head threads as fast as they can. Also they get the engine warned up first. I have read that timesert may be a better thread repair than heli-coil. I have done a drain plug in an aluminum case, and used a heli-coil wannabe. It was not very successful as the plug screwed in at an angle when done and did not want to seal. The pan 'boss' was very think, which I did not know, and apparently I got it drilled poorly. The original had been kind of butchered when I bought the bike, so that likely got me off to an angled start. The metal was likely too thin for a heli-coil to work properly and I should have drilled & tapped from the get go.
It makes sense that an impact tool would tend to break the threads free of each other, but it just seems wrong to use one. I will have to think if it is a good way to go for me should I have sticky plug threads.
I should mention about RTV... There are brands that are "O2 sensor safe" that apparently will not kill the O2 sensors, so be aware that generic RTV can damage the sensors. I think a byproduct coats the sensor so it no longer has 'touch access' to the gases flowing past.
tom