C-15 6NZ stumbles / pops / power drops

My 2003 Pete 379X , CAT C-15 / 6NZ has been driving me bonkers and i need help.
12 months ago i bought this beautiful Pete. Fresh paint, 1 year into a 4 year CAT platinum warranty, tranny just rebuilt, new diffs and the list goes on.

I drove it like i stole it before writting the cheque, loaded trailer in tow, and it drove tip top.
Before putting it on the road, i left it at the shop it was regularly serviced at as they knew its history, and the techs there are all licensed, CAT specialists old school farming community kind of guys. They installed awet line for me, serviced it, and a week later i picked it up (that was about 12 months ago, Sept. 2016)

Ever since i picked it up, the engine has what seems like half a injector misfire. Pops/stumbles/ shakes and power drop off. CAT did cut out tests 3x. Fuel pressure has always been tip-top at 80 psi on idle, 100 at 1500 RPM. Entire fuel system has been redone, New fuel lines (supply and return) new divider valve, divertor valve, fuel pressure regulator, primer pump, primary fuel filter head, fuel pump, even a "Air Dog" fuel air seperator system was installed even though no air was found in the fuel. All new engine wiring harness, injector wiring harness, and CAT had the truck 3 times, once for a entire week. CAT flipped a coin and installed 2 new injectors even though they couldnt isolate the problem.

Lots of top-sets done, cam sensor, crank sensor, fuel temp sensor, barometric pressure sensor, air intake sensor and much more. Fuel tanks were both dropped and pick-up tubes checked for cracks, all good. Intercooler was pressure tested, fuel supplier was changed for a month, speed sensor and wiring to it, was changed. I check regularly for electrolysis in the entire engine, all fluids etc, no problem there.

In a few days, the entire exhaust system is being dismantled to check for restriction(s) as im on my 4th exhaust manifold because the slip joint seals and manifold mounting seals keep blowing out ( Thank goodness CAT warranty covers it every time, mind you i was told CAT has had many such issues, as it is somewhat common)

The strange thing is my problem comes and goes all day long.

From a stand-still, (traffic light or similar) engine pulls and feels great through all bottom gears. Soon as up shifting gets further apart (time wise) the stumbling / popping starts and only gets worse.

No longer am i focusing on fuel supply or return, both seem to be functioning as should, more so now that the entire fuel delivery and return are new. (i even built a fuel hose , stuck it in the drivers side tank, drapped it along side the top of the fuel tank, under drivers door, and right into the primary fuel filter head. Still it stumbled and popped. Then did the same with the passenger side fuel tank, no change)

Anyway, now im focussing on the ECM, the batteries (broken cell causing voltage issues ?) and the alternator. All this week (its only Tuesday) ive been turning on every electrical draw on the system, then everything completely turned off. Keeping a close eye on the volt meter, the AMP meter and so on.

And as i sit in my Pete having finished my day and type this asking for help, all my lights are on, my A/C is on, the blower (in cab air flow) is on, my fridge is on and finally, my in cab ceiling etc lights are on and 3 times i thought a huge bug or whatever must have flown on my dome light as the light keeps dimming down, and back up again. Maybe im onto something here !!

12 months back my stumbling was violent, and i mean nasty violent, to the point i booked the next day off thinking i was close to breaking the crank !!! thats how bad the engine ran. Today, 12 months later as i keep chasing the problem, the stumbling / popping and power loss is much less, but still there.

IS THERE ANYONE OUT THERE WHO CAN OFFER SOME SUPPORT ? Ive spoken to "CAT Man" on that pay for help app "Just Answers" but he couldnt help at all either. If i lived in the U.S. , id be at "Pittsbugh Power", as they advertise being able to "fix the problems the other guys cant" (and XM Radio / "Road Dog Radio" show Kevin Rutherford endorses them, and Kevin doesnt do that with just anyone / any company)

Again, i would be very grateful for any help you may be able to offer.

(Appologies for the length of this thread. Just trying to fully convey my problem and need for support)

Thanks again.

 

Thanks for you help and support.
All injectors have been taken out twice, once by CAT once by a CAT tech who is retired and very knowledgeable.
If theres air in my fuel i will be shocked as to where its coming from, as its there, and then not, If i roll down a grade, stop at a light, or any sort of backing out of the throttle, all runs tip top, but only for minutes, or if im foot to floor for a hill climb or high torque is needed after a stop (and i mean hefty power dose for prolonged period of time) she pulls great. But the slightest backing out of the throttle and its back...popping and stumbling.
Thanks again for you support.
I will keep you all posted, as this one is a challenge !!!

 

Thanks agin for everyones replies in effort to help resolve my one year (and counting) problem.
Many times i changed all fuel filters, dumping each into a seperate ziploc bag and hanging it on the wall in my shop to see if anything, any sediment at all settles in bottom of these clear ziploc bags, but nope.
One time when this all first started, i built a fuel line, stuck one end in the fill cap on drivers side tank, and the other end directly connected to the primary fuel filter housing so all fuel would be properly filtered. Went truckin with this hose drapped on the top of drivers side tank, over my drivers step and to filter head. No difference. CAT even changed the primary fuel filter head on one of my visits there, and checked everywhere for air, but no air was getting to the head at all.
Another thing i forgot to mention. I hear "TICK...TICK...TICK...TICK" coming from engine compartment when it gets to popping and stumbling really bad. The same kind of ticking you get from a bad injector. Strange is that if i get on a highway from a ramp, foot to floor to get speed up to highway speed (i pull 5 axle trailers, 140,000 LBS all day long) engine pops and stumbles through 1400 rpm, but therafter (1500 to 1650 rpm) it clears up, and purrs as it should. When i engage my PTO to dump, i rev engine to 1300 ( + - ) and engine runs great, as it always has when not under load. Id swear its sucking air and then, due to faster engine and sucking more fuel from tanks, the faster fuel travelling slams the door on the opening where it sucks air through, i dont know, it sure computes that way when i think what the hell is going on. All i do is think,,,think,,,think, is it the ECM,,,,is it sucking air....is it my alternator not converting the A/C power (which is what alternators initially create before converting to D/C current) to D/C power.
Any ideas anyone may have please please forward them, its all so greatly appreciated guys.