As a disclaimer this post is going to go deeper then just talking about a tune. Just so no wrong category stuff pops up. Hey guys im making this post in regards to my 06 sierra. Besides all the cosmetic crap. 31” tires on 20” stock rims. etc etc. It does still have 342 rear. Which I know is a grandpa rear end (spare me). the only mod besides a canned tune is a cat back exhaust. I loaded the canned diablo 93 tune in this truck about 4 months ago give or take. it seemed that it took a couple hundred miles until i started noticing a difference. Even though it was a canned tune it still made that truck run good. shifts firmed up. sped up. Acceleration was better. etc etc. about a month ago I noticed that if i was at 2100 rpms and in second gear that my truck would no longer take off. It more or less just sluggishly climbs. Almost like a truck with no back pressure. Anything below 2000 the truck is still able to gain the power it needs to take off. If im cruising at 60mph And drop the old hammer, the truck shifts to 2nd and once again takes off. Its just that for some reason all of a sudden ive lost my torquey, downshift acceleration during one particular rpm range. and in one particular gear. I dont think its a torque converter issue. Because at certain ranges I can still take off. Also, The truck shifts through all gears fine. I have noticed a slight power loss/torque loss overall here lately. Through all gears. which is understandable being a 120000 mile truck that ive been hot rodding around in for 3 years. Ive cleaned the maf. Changed plugs and wires. ran injector cleaner through it. Ran an entire fuel system cleaner through it. Seafoamed the top end. This truck is fly by wire btw. It has two different throttle positioning sensors. One by the TB and one under the gas pedal (I think). I have not done these yet. 60 psi at the fuel rail during idle. I have not done a compression test on it yet. It has heavier duty calipers on it with ceramic pads. I do get a lot of brake dust from them but I truly do not think they are dragging. Tranny fluid is fine. Tranny temp is fine. This loss of power seems like a program issue but i dont understand how a tune could magically change. If I go into datalog mode and watch my throttle both percentages on my tuner show normal increases and decreases all the way from 100% to 11% or whatever number its supposed to be at idle. Which i assume means my tps is operating fine? Im not for sure. I have no clue what im doing. its why im here. I tried reinstalling the tune. Which was scary because i encountered some strange electrical glitches. The tuner didnt wanna load the tune. It took a few tries and im probably lucky that I didnt brick my damn computer. Ive installed new window switches. Although aftermarket they still run all the OE configurations. I had my remote start unplugged. The only other electrical anything ive put on this truck is an led light strip. Could be the cause? Maybe. For some reason my truck doesnt want to shift firm now like it did upon the first tune loading. This is an predator 2 platinum (i know, spare me). But i still never had issues with it. And when i say glitches im talking my windows wouldnt row down normally. My satelite radio was glitching. it was wierd. Maybe this should be a posted in a tuning category. I dont know im covering a broad spectrum here. sorry in advance. Im just totally lost at this point. Is my butt dyno just used to the truck? Am i imagining things? Who knows. Any input is appreciated.

 

Can you log fuel pressure during a pull? I bet she is starving of fuel and the pump needs to be replaced

 

I cannot log fuel pressure with the p2. Atleast I dont think so. The only thing i could do is check it with a gauge while in park and somebody giving it gas. Unless you guys know another way. I just replaced that fuel pump last year while I had the bed off doing the suspension. I replaced it with a delphi pump. If that pump went bad again it would have had
to either been defective, or its from running 93 through her. Ive thought ive taken good care of it. Not letting it get below a quarter tank etc. Thanks for the response ill look into it more. But if im taking that bed back off i might as well find a new bed while im at. Also I gave her some gas going around a curve tonight. We are getting pounded with rain. Still had enough *** to hydroplane and send her sideways at 35mph. I dont recommend it.

 

You state that it magically changed for the better when you installed it, but can't believe that it magically changed for the worse?
I'm not saying that because I think that is your problem, I just said it to make fun of you.

 

Lol no I see your point. I really do. Thats why I reinstalled it. I just would love to know how it would change. My driving habits certainly havent changed. Nothing internal within my truck has been modified. There was a shortage of 93 last month. Alot of stations didnt have any at all. Maybe im being ripped off with shitty gas. I dont know. Maybe i need throw a cam in it. Get a custom tune.

 

See now you are identifying the issue!

 

You need to check if you're getting fuel pressure as mentioned and if you are getting knock (false or real).