Temperature drop does have an affect, I've had to do some tweaking on mine. That drastic though I'd suspect a fuel delivery issue, if it is the pump the Walbro 255 is a popular drop in replacement. I want to say the part number is 340GSS but I'm probably wrong.
2006 SilveradoLittle Black Bitch
It has done it since Sept. so the cold has not changed it. I am definately guessing fuel issue since I replaced a lot of these pumps when I was a GM tech. Any good sponsors on here to buy from? Hopefully it gets nice soon so I can check it out. Too bad I can't take it with me to Texas next week!! I am sure the weather there will be much better.
tanz45 - At least my Trans Am sits on the ground. I love them lifted or slammed as long as they are done right!
Rubie
Last edited by iowackers; 12-08-2010 at 04:43 PM.
2006 GMC Sierra 1500 HD Crew Cab 4X4, 6.0L, 12" CST lift, 37" tires, CAI. Vinci cam 210*/218* LIFT .587 / .595 LSA 114*4A, Power Slot rotors all around with ceramic pads, Rebuilt 4L80E with shift kit and billet converter.
Rubie
Nelson sells the drop in GSS340 Walbro 255 you need.
1969 Chevy RCLB C10 350/TH400 SOLD
2007 Chevy RCSB 4.8 4x4 LS SOLD
2008 Chevy RCSB 5.3 4x4 LT SOLD
2010 Chevy CCSB 6.2 4x4 LT SOLD
2005 GMC CCLB DRW 6.6 Duramax 4x4 191,000 and counting
2013 FORD CCSB F350 6.7 Powerstroke 4x4
Only two things it could be IMHO and both pertain to fuel.
1) Injector size
2) Fuel pump not keeping up
You need to check to see what your injectors are doing and make sure you haven't maxed them out (I doubt you have). Secondly, check to make sure you have the fuel pressure you need at WOT. You can check this by attaching a fuel pressure gauge at the Schraeder valve and placing it in a position OUTSIDE OF THE CAB where you can see it while driving. Check to see if you start losing fuel pressure at WOT. If so, I bet it's your pump.
Just some suggestions, but do as much diagnostics as you can do before you start replacing parts. Gunna save you a bunch of money in the long run.
- Paul J.
2006 Silverado LT3 L33 Z71 - Mods: K&N Air Filter; Taylor Wires
2008 Azera Limited - Mods: (Yah, wife's car ... not happening)
(SOLD) 1994 Camaro Z28 - Mods: (Too many to mention)
(SOLD) 2004 Suburban 5.3L Z71 - Mods: Flex-a-Lite 292 Monster Fan
(SOLD) 2000 Silverado 5.3L Z71 - Mods: (NTIKO)
(SOLD) 1991 Suburban 350 2WD - Mods: (NTIKO)
a friend of mine has a stock fuel pump and 28lb (maybe 32, cant remember) injectors supporting well over 500whp FWIW...Originally Posted by Paulster2
01 Silverado
hook the fuel pressure gauge up and run it up to the windshield and shut the hood till it latches but not all the way. that way you can see the fuel pressure at WOT while your goin down the road. And if your running that lean be careful at high rpm its not good on the motor
2008 GMC Sierra SLE....370ci LY6 with some goodiesSOLD
1995 C2500- LS1 swap with a mp112
build thread- http://www.ls1truck.com/forums/lsx-t...-ls1-swap.html
Finally went for a ride today with the fuel pressure gauge. 50 psi at idle. Very responsive with throttle movement. WOT was 58 psi. Truck still feels weak and at 5000rpm it dropped out and went really lean again (19.2 AFR) No codes. I have gotten 1 or 2 O2 codes in the last couple years, but that is all. Any ideas? Check injector duty cycle next?
2006 GMC Sierra 1500 HD Crew Cab 4X4, 6.0L, 12" CST lift, 37" tires, CAI. Vinci cam 210*/218* LIFT .587 / .595 LSA 114*4A, Power Slot rotors all around with ceramic pads, Rebuilt 4L80E with shift kit and billet converter.
Rubie
Yes. IDC next. It may not show a clogged one though.
1969 Chevy RCLB C10 350/TH400 SOLD
2007 Chevy RCSB 4.8 4x4 LS SOLD
2008 Chevy RCSB 5.3 4x4 LT SOLD
2010 Chevy CCSB 6.2 4x4 LT SOLD
2005 GMC CCLB DRW 6.6 Duramax 4x4 191,000 and counting
2013 FORD CCSB F350 6.7 Powerstroke 4x4
statements like that are so misleading, a cam and headers will max out the stock setup on 6L's.
we do fbodys all the time here, a big cam and headers maxes out the stock 28lb injectors.
doesn't sound like a safe setup, at well over 500hp...
To the OP, if there's anyway to get logging going, send it on over, that'll help quite a bit.
Typically, with a cam like that in a that engine, with longtubes, we can keep a/f ratio in check.
Maybe the injectors are a little dirty/slow and you need bigger ones, or maybe we just need to add more fuel to the engine.
If it is out of injector, trying to add more fuel from a retune isn't going to work.
lmk,
allen
Nelson Performance
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