99 6.0 spontaneously cutting out under WOT??? Help please.

[BRONCMAN]

My truck is in my sig and also has a diablosport predator tuner. Every once in awhile when I romp on it the truck acts like it is getting no fuel & does it for about 20-30 seconds then starts running fine again. At first I thought that this may be the fuel pump so I replaced my fuel pump & filter. The fuel pressure regulator was replaced about 30,000 miles ago. I have monitored Real Time Data in the Predator while this was happening & noticed my LTFTs (Long term fuel trim) are in a normal range under WOT (2-5%+) & that there is no knock retard. All cylinders misfire though when this happens. Someone said that it is probably my coils, but why would all cylinders go out at once?? I have another complete 01 6.0 LQ4 but it has the square coils & mine are the round style. Will the square ones work in replace of my round ones if that is the case? Any help would be greatly appreciated as I have to move in a week & will be towing a trailer over steep grades & im not looking forward to it cutting out again. Could it possibly be the tuner or maybe that autozone FPR with about 30k on it??

[BRONCMAN]

Anybody???

[oleshifty]

I'd probably lean towards a cam/crank sensor type thing. Possibly loose TPS or MAF connection.... no SES light?

[BRONCMAN]

No. No SES light. Im thinking its something to do with my fuel pressure regulator. Yesterday I towed my trailer over 500 miles and when going up steep grades (7%) it would run awesome then just start losing power off and on. 1 time I was down to 20 mph under WOT. I started pulling over whenever it would do it & with the truck idling I would pull the vacuum line off the FPR then rev the motor plug it back in & it would run fine for about 50 miles before doing it again. I noticed when I pulled the vacuum line it would start idling faster by maybe 50 RPM. I have heard before that if you pull the vacuum line on the FPR that your truck should start idling crappy, but mine seems to run better. Like I said earlier it was replaced before, but by one from Auto Zone so I think im going to run to town here in a little while & go to NAPA auto parts & get another one. Hopefully that will solve the issue... I will keep you guys posted.

[pl4yboy]

Check the injectors. They may be clogged.

[BRONCMAN]

Whats weird is that the truck runs awesome most of the time, then this happens & it losses almost all its power. I did get a P300 (misfire) code but thats it. It might possibly be a tps as while this was happening yesterday when I was data logging I noticed my engine load was only between 40-50%. I also noticed it did take about 5 seconds for my arbitrated throttle position to show 100% after it was at WOT. I held off on getting a new FPR at the moment and just popped mine off earlier & made sure there was nothing in the screen. I also got a bottle of sea foam ill run through tomorrow. I figured i'll suck about 1/2 the bottle in a vacuum line & pour the other half in the tank after I get down to about a 1/4 tank.

[RedHeartbeat]

sounds more like the fuel pump is petering out to me.

[BRONCMAN]

Fuel pump was ruled out the hard (expensive way). It was replaced 2 weeks ago along with a new filter ofcourse. These same issues also occured before then. I figured it was the pump cutting out every once in awhile & replaced it.

[SCIV]

Check your grounds.

[BRONCMAN]

Checked grounds this am. All good there. Im going to drive it more here today & see if it will still do it.