Thanks for the input. The offending plug looked like new - in fact the entire set has around 3k, the number six gap was .044, my underhood label shows .042-.046. The Seafoam was just a though to clean the intake tract from all the soot that is sure to be there from 245K miles, not necessarily to clean the injectors. I have over the five months of ownership ran several cans of techron through the tank just as a precaution. The number six injector has poor access, I will get stethoscope with a long prob and have a listen. Bratko.

 

Ok, good feedback on the #6 plug condition & spark gap.

On the Seafoam ingestion, I assume you want to inject it via a vacuum line, so choose one that connects to the throttle body & follow Seafoams instructions, so as not to inject too much too quickly & hydrolock the engine & bend up something important. Maybe consider using a metal sports needle like the kind used to inflate foot & basketballs, attached to the vacuum tubing end that's inserted into the Seafoam container, as that's less likely to have the engine suck in too much too quickly & hydrolock it.
I'd consider waiting until oil & filter change time & do it immediately after that kind of service, so you drain any residuals & muck its loosened & made it past the rings into the oil sump.
Seeing as how you've used several Techron treatments, the injectors, intake valves & combustion chambers are likely as clean as your going to get them with aftermarket treatments. Did you use the 20oz size & do the high rpm part of Fords 4.0L decarb TSB during the Techron in the gas treatments????

We can fashion a stethoscope listening device from a wooden dowel, tubing, hose, screwdriver, broom handle, ect, one end on the subject, the other to our ear.

Will be interesting to hear how fuel trim & the #6 miss react after replacing the other O2 sensor, so you have matched O2 sensor switching range & speed on Both cyl banks.

 

Good evening, just some more feedback. I got my hands on a spark tester, and the offending #6 cylinder has a nice consistent spark, even when the scan tool was showing a miss fire, there were no changes to the spark in the tester. I tired listening with a stethoscope, but as many of you know access to the #6 injector is miserable. Honestly I could not be certain that I was listening to the #6 injector. I heard nothing unusual - or different in the vicinity of cylinder #6.
So I went ahead and pulled the upper intake, and checked resistance of all injectors, and all including #6 showed 14.6-14.8 ohms. The intake tract looked typical and full of black soot. I DYI cleaned all injectors and swapped the # 4 and #6 injectors, and put it all back together. Currently running the same- not bad, and not showing any miss fire, let the truck idle for about 30-40 minutes and no miss fires. Time will tell if the miss fire moves to #4, I will try to drive the truck as much as I can this weekend, and I log as I drive. Take care Bratko

 

Ok, good trouble shooting & feedback. Looks like the fuel injector resistance is within range & well matched. Will be interesting to hear if the misfire returns.

 

These Ranger Forum sites seem "OK" but suggesting all this random testing and replacing of parts is ridiculous and seems to me that Ford's designs and design team is "boo boo". All this is well meaning, but the shear volume and lack of problem resolution shows either the people posting don't know what they are doing or I am correct about FoMoCo. This baloney doesn't deserve any mustard and I am selling my piece of Ford doo doo next week. What a sketchy care company; sell now because you will be haunted by constant repairs and no answers from Ford or any of their so-called "master mechanics". I call them "master mechwreckers", they rip-off women and unsuspecting buyers and I for one will never buy another Ford. What dog do-do Henry......

 

Thank you for that wealth of information. You joined in 2011 and it took you that long to compose your first post? Better stick with trying to get them to supersize their order....

 

My apologies for the long delay- to much work not much time.
I wish I could report back something like the miss went away or it moved as I moved the injectors on bank 2. I do have the P0306 back, and it's the same song second verse - idle. I wish I had the money to just buy a new injector when I had the intake off.
I did replace the up stream B2 O2 sensor with a new Bosch unit like I did with B1 in September. I am still convinced the ignition system is sound, I will now take a closer look at the fuel system. I have been logging some trips, and both banks fuel trims seem higher than desired. After a drive cycle the LTFT on B1 is in the negative teens, and B2 sometimes approaches - 25 at idle. Still around- 10 at normal highway cruise for B2 with B1 usually around -5. This does not seam correct although I have never got any rich codes, only the P0306. I am going to measure the fuel pressure in a bit and repost the values.
With this many miles I guess the injectors could all be bad on that bank even though they passed resistance and are clicking- maybe a runny nose? I am looking for the company that rebuilt the injectors for my 95 F-150 w/ the 4.9L big six I had a few years ago. A reman head from LKQ is $200, does that seem reasonable.
Once I have my tax refund in hand I will have more options.
Thanks for reading. Respectfully Bratko .

 

Lets see I like to read, investigate, research and inquire before I speak; it is obvious from your poor use of the English language that either you couldn't complete high school or your another south of the border mexi-mechanic. The truth hurts homeboy, suck it up and don't act like a b*$#@.

 

Just re- checked the fuel pressure. KOEO 50 psi, it took two primes to get there. Engine at idle 50psi, after shutting off the engine, held the pressure for 30 minutes. That to me seems to rule out a runny nose on the injectors. As of right now at idle the B2 LTFT was about -17, but the STFT for bank one was about +8, the B2 numbers we just slight lower. Starting to run out of ideas, and circling back to a bad valve or seat on #6.

I was able to get it through inspection. It honestly runs and drive just fine, if I sit at idle and it is mis firing am I doing any damage to the cats?

Thanks for looking Bratko.

 

OK, more good trouble shooting feedback. So, lets think about this some more. Seeing as how the miss on cyl-6 didn't follow the fuel injector swap to cyl-4. it would suggest that the #6 cyl miss trouble code problem doesn't have anything to do with the fuel injector.

With the spark plugs, wires & coil pack having been replaced with OEM/Motorcraft parts without a change, it would suggest that ignition isn't the problem.

Kinda leaves you looking at the cyl-6 valves, or maybe a sticking piston ring. With the #6 cyl pressure varying between 115-120 & all passenger side cyls reading a little low, maybe consider a over night cyl piston soak to see if it'll respond.

Seeing as how fuel trim is still mucked up after replacing Both upstream O2 sensors, when you had the upper intake manifold off, could you get a good look at the back side of the intake valves for deposit loading??? Thinking maybe with all the mileage on this puppy, heavy intake valve deposits could be absorbing fuel & corrupting fuel trim.

How does the top end of engine under the valve covers look for deposit type & loading???? Wondering about valve stem deposits like varnish, causing #6 to intermittently hang up a little & not seal.