Rogan

sub 10k miles on new Bosch OE injectors RaceMe Pro tuned (60hp setting, #3), deleted. 5" FloPro exhaust For a long time, now, I've been getting a fuel derate under heavy throttle loads (like climbing a 4-5% grade in 5th or 6th) at like 40% or more throttle percentage. As an example, logging with my XTOOL A30D scanner: 60% throttle 5th gear about 55mph loaded or empty, doesn't matter Fuel pressure requested set point: 21000psi Fuel pressure Sensor: 15000psi (more throttle decreases this pressure, I've seen it as low as like 8000psi) HPCR Fuel Pressure: follows fuel pressure sensor After about 5-8 secs of this gap in requested pressure, the Derate Counter increments by 1, the engine gets flat (100% throttle makes no change) and the overhead console dings "See Dealer". no codes are stored... Things I've done: I've updated the tuner's firmware re-flashed the truck replaced fuel filters replaced the Fuel Pressure Sensor Replaced Fuel Pressure Relief Valve with a Plug Re-shimmed OE FPRV Replaced with Bosch new FPRV Changed to a lesser tune, as well as a higher tune tried stepping up the rail fuel presser no change, set back to stock Last thing, I've ordered a FLEECE 170 lift pump, that will be here tomorrow.. The 'NO CODE' part is a MFer, since that gives me absolutely no direction. Thoughts? I'm at a loss, and I've been chasing this issue for a very long time.

Wondering if it isn't the EGR cooler. Started the truck up the other day, park brake on, hit the cruise, then set.. idled up to 1200, EB on, I let it warm about 5 mins (was 19F out). Came out to get in it, and saw a puddle of coolant toward the RR of the engine... chased it down, it appeared to be the fitting where the EGR cooler hose hooks to the vertical steel nipple out of the head (just forward of the heater port).. Drove down to Auto Zone for a jug of coolant, left it running, no high idle, no EB on.. came out, no drips. Topped off the overflow jug and monitored the truck the rest of the day for leaks; none found. The next morning, I did the same thing. Came out to leave, 3 puddles: same as before at RR of engine, but also one at LF and one at RF of engine. Further inspections found the upper coolant hose at radiator leaking, as well as pushing coolant at the cap/overflow hose connection.. Turned off EB, dropped idle, let it idle for another 5 mins. Leaks stopped.. Think this is back pressure pushing through the EGR cooler or something? Engine has about 1500 miles on a full rebuild. Never leaks or loses coolant unless I force the above scenario. Thx

That's wonky! lol Guess I'll have a poke around to see, then. Thx

It's a VNT....

I'll take a look, but I doubt there are any. On that note, I've only ever seen a max of about 21psi, but I'm not sure what the 6spd max boost is, anyway.

21SEP, as stated a few posts back, I replaced the air filter. Injectors are new Bosch with < 2000 mi on em. Matter of fact, the entire engine is < 2000 mi. I was surprised, too, with the fuel economy (or lack of) that low. I miss the days of my '96 12V 5spd getting 27mpg @ 68mph lol

265-70-17. rolls free.

Week later, still good.. 70mph, 750-775F, 13ishK rail pressure, zero boost. 14.5mpg.. UGH.

cool cool. thanks for checking! Question: with that high of rail pressure and EGTs, would that contribute to less MPG? I was getting 15-16 on a highway trip 200mi, at 70 on cruise.

much appreciated, sir.

Hey, John.. So.. UPDATE.. My OEM intake tube was all cracked and full of holes in the rubber pieces, so I bought a "cold air intake w/filter" for an interim fix. I threw my GoPro under the hood for S&Gs and pointed it to the air filter.. Low and behold, the filter was sucking closed rapidly.. So I ran down and grabbed a 4" inlet K&N (again, this is a temp solution, as I'm trying to source an oem intake pipe so I can reinstall the stock airbox) and swapped the filter.. the truck seemed a tad more responsive, throttle-wise. Took it back out onto the same stretch of road I was on when I went to pick up the new filter... Mind you, on the way back from getting the new filter, with the old one still in place.. 60mph, 0psi boost, 1100F, 15k rail.. After the filter swap, same section, 60mph, 6th gear as before.. 0psi boost, 700F EGT, ~12k rail pressure.

This is just cruising @70mph fairly flat interstate.

I just stuck gauges in my 07.5 DRW. I noticed on flattish ground at 70mph, 6th gear (G56) I'm at 2150-2200 (3.73) RPM, 900-1100*F, and about 16-18k RP. Boost is zero.. In my old '96, it'd carry about 6-8psi, and about 750-900F EGTs.. Is this normal for a 6.7? No boost, and EGTs that high? It's all stock. Thanks.

Good luck finding a 'deletable tuner'.. I almost did mine, but waited too long. Now all the local/semi-local shops are being eat up with EPA fines and have stopped even selling them.. sucks.. I have 'fixed' my EGR, but I am on stock, OEM everything, including tune... it's still lethargic and I despise the G56. lol

I checked 'em out, but the smallest in the kit was 5mm, which is too big. Advance had 3 o-ring that were the right size, but that's it. I'll try Lowes tomorrow I suppose.