Mid-range hesitation problem

Hi guys. I haven't posted much on here because just about every question I can find the answer to by searching through google. I've done that this time for hours, tried all kinds of interesting fixes and, still no luck.

Backstory:

After blasting through the desert for an hour or so, we usually stop for a beverage and take in the sights. Every time I would start the truck to leave, it would run on 2 cylinders and eventually pick up to run "normal". Normal is idle that likes to hang for a while before coming down. 4-5 4.0 rangers I've had drove like this.

As I got ready for a recent desert trip I drove it 40 miles to a gas station near my buddies shop. Filled up about 30 gallons of fuel (42ish gallon tank). Of course when I started it, ran on 2 cylinders for 30 seconds, picked up and I was on my way. After being at my buddies shop for 30 minutes I went to move the truck. Would only run on 2 cylinders and wouldn't pick up. Reset the computer, and still nothing. After about 10 minutes of playing with it, it picked up some more cylinders but not all of them. Decided to leave it at home and hitch rides all weekend.

Once I got home I started to do the usually spraying brake clean everywhere, pull plug wires and see if that cylinder is dead or not, ect. Was fed up with the brake clean so I sprayed a ton down in intake to see if it would change the idle. To my surprise the stuff we were using did not. Anyways, pulled the upper intake manifold off and found that all cylinders BUT #5 were wet still with the brake clean. Weird.

Decided to pull the motor because I'd rather work on it on the stand, and had solid motor mounts to install. Once I pulled the lower intake off, I was confused. Both the intake manifolds had carbon build up in ALL the cylinders. However the head had carbon build up in every cylinder but #5 as you can see in the picture below.

Here is what has been replaced during this ordeal:
Intake Manifold Gaskets (felpro)
Valve Cover Gaskets (felpro)
Spark Plugs gaped at .054 (motorcraft)
Wires (motorcraft)
PCV valve (motorcraft)
Coolant temp sensor for the computer (motorcraft)
Fuel pump was swapped for a new one (duralast)
Fuel Injectors, re-manufactured
Fuel Filter (motorcraft)
Oil Pressure Sensor (still pegs the gauge) (motorcraft)
EGR DPFE sensor, had a code for excessive flow
EGR solenoid sensor, not sure the actual name
MAF sensor is 500 miles old, behind a UMP filter, and it was cleaned (duralast)

As of right now it has a minor miss through the mid-range free reving it. Under a load it's a considerable miss until about 3,500 rpms. Appears to have lost power after that.

Tested:
Fuel pressure holds steady at 30psi and does not fluctuate under load. Goes up with throttle position
TPS appears to be linear but occasionally did weird stuff. I couldn't tell if it was my movements though.
Swapped a brand new coil, no change. Cleaned the old coil, and added an extra ground to one of the bolts with change.
Long Term Fuel Trims show 25%.
After about a dozen test drives (maybe 5 total miles) it popped a cylinder #5 misfire.

I'm stumped at this. Any suggestions? Going to try a good TPS in the morning when I return the new coil.

Picture of the odd cylinder 5 cleanliness



I live on backroads, it was safe



and the truck you're helping me fix

Have you done compression tests on all the cylinders?


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Diesel Mechanic said:

Have you done compression tests on all the cylinders?


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Click to expand...

I have not unfortunately. I did check the problem cylinder 5 before I pulled the motor and it registered at 180 and somehow with the upper intake manifold off it started, and jumped up to 210 psi. If I can find time I'll get a compression test done on the rest of the cylinders, it is a real PITA with the cage setup though.

Yesterday I plugged every vacuum line and that did not have a change. Found I had my o2 sensor bank 2 and the post cat (mil code eliminator) o2 sensor swapped. Figured that would fix the problem, but again no change.

What I did notice on more test drives is the problem arises when I accelerate more. So lets say I'm at 5/16 throttle position and I press it down to 7/16 throttle position. It will misfire for about 2 seconds then be fine as long as I keep my foot perfectly steady at that throttle. It SEEMS to be independent of rpms but is more noticeable at lower rpms.

In the video below right at the 23 second mark I accelerate but you can hear how the motor struggles. It might take a couple times listening to it with the volume turned up, but it's there lol.

I spent hours playing with the cam position sensor until I finally got that right, and once again, no change.

I blocked the egr with a makeshift cork gasket gasket block off plate. That also did not fix the problem and no it did not blow the gasket apart.

Tried to check timing but failed at that with an old school timing light my father has had for decades.

I have come to realize the problem exists only when you change throttle position. It appears to only happen at less than 1/2 throttle and also less than 3000 rpm. The thought is a vacuum leak somewhere because after 1/2 throttle or 3000 rpm the motor is pulling enough air that the vacuum leak is within trim-able values.

Getting a new MAS that I know is for my motor (it's possible autozone sold me the wrong model number) and we'll go from there. Getting real annoyed so I'm driving the truck around Hoping it shits out so I can put an SOHC motor in or a 5.3 and 4l80e...

What year computer are you running?

You were monitoring fuel pressure, what was it?
Engine running
Engine and key off
Key on first time engine off

Coil pack does have odd wiring
3 4
2 6
1 5
front

I still mess up the 5 6 4 side, even though I KNOW it is correct.