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Discussion Starter · #1 ·

03 Silverado 2500hd 6.0 5speed 4x4.

Within days of buying it I had the PCM tuned by blackbear to try to help the horrific throttle response. It helped some, but is still insane.
Ive ignored it for over a year now, but today decided to actually watch the throttle and see how slow it actualy is.

This might not be a huge issue on an automatic, but on a steep hill, with a trailer, and manual trans, this is a pain in my ass lol. Ive gotten used to it, but it bugs me every time i drive it.
Feathering the throttle, such as taking off under load or on a hill, the throttle just twitches, doesnt even try to open at all.

Everyone tells me i shouldnt be able to tell the difference between DBW and a Cable Tb, but I dont see how thats possible.

Does this video look about normal for you guys or is it indeed slow? Takes nearly 2 seconds to open when the pedal is put to the floor.
Thanks
 

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I don't know about GM or 2003 models but other drive by wire models have what some call 0 to 60 limiter built in the tune. It's part of the torque control so you when you gas it, there is a built in delay. Do a search on it. Some tuners can remove that.
 

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Discussion Starter · #4 ·
All torque management is turned off. Everything in the tune Iam told should be set for instant response.
Ive tried 2 other throttlebodies, ive swapped the TAC Module with another known-good one, ive VERY thoroughly cleaned both throttlebody and MAF sensors, truck has fresh tuneup, no intake gasket leaks that I can find.
Throttle response seems to be ok once the RPMs are over 3k. Anything under, and your talking a few seconds before the idle changes AFTER you have made input on the fuel pedal.

Now, in addition to being painfully slow to respond, the truck randomly dies when coming to a stop, or between slow gear changes but ONLY when its very cold out.
Any ideas now? No codes that I can see with my scanner. No CES light. Related issue?
 

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2004 Sierra 3500 6.0L, auto, extended cab, cab&chassis, upgraded to 4wd
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You may want to check that you are getting steady fuel pressure at the rail, both at idle and when you rev the motor.

I believe it should be about 55 psi (not 100% sure, as I believe the '03 has a different setup with a fuel pressure regulator at the rail with a return line, my '04 the fuel pump in the tank is responsible for keeping the pressure correct with no fuel return line).
 

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Discussion Starter · #8 ·
Ok I will check into getting a fuel pressure gauge on it.
Iam not sure if the pump or regulator has ever been replaced, I just know the lines and filter are all new.
 

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In neutral if I stomp it, there is a slight delay. I would say its less than half a second from the time I stomp the gas till the time rpms increase. While driving down the road I cant really tell. My truck is an auto though but I don't see how that should matter. However the Nv4500 in your truck is weaker than the 4L80E so I guess its possible theres something built into the programming that prevents rapid rpm increases and an issue is exacerbating that. Hope that clarifies my last statement a bit.
 

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Discussion Starter · #10 ·
I understood. It is possible there maybe some hidden torque management type setting we can't find it guess.

A coworker found an identical truck to mine except I think his is an 04, less miles, bone stock, and he claims his response is instant like any other vehicle. Maybe the 03s are tricky for some reason ?
I have to figure it out sooner or later.
If I can't, might have to do something drastic and stupid like convert bsck to cable. It's THAT annoying.
 

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2001 GMC Sierra 2500HD CCSB
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Throttle response with DBW is a pretty common complaint. I think most people who get a custom tune have it "fixed" enough to not notice it or it didn't bother them to start with, but then most people are behind autos which is probably a big factor here. Since you have a more direct control of your power all the time the throttle delay is probably really noticeable.

Someone just posted a thread of a device that tricks the throttle into reacting faster. I'm not sure if it would work on your model year but may be worth looking up.

I found an old thread mentioning it, product by Sprint Booster. Sprint Booster

There was a recent one I just read about someone installing it and really liking it and now I can't find it. May have been a different brand?
 

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hahaha there it is, the dumbest non helpful comment you have made to date!

OP- I know what you mean, when I drive my fathers OBS its amazing the instant throttle response, then I get in mine and its just bleh.
 

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Discussion Starter · #14 ·
Holy useless reply batman! I was waiting for such a reply. Every DBW thread out there has one.
Some wanna be comedian has to chime in and either claim DBW is faster and the OP is just confused or hallucinating, or some other useless statement like the one shown here.
Run along, troll :mrgreen:

There is a reason my throttlebody takes several seconds to go from closed to open, but closes instantly when the pedal is released. It should open as instantly, PERIOD. I have seen numerous videos of DBW's reacting just as fast as cable, so it IS POSSIBLE.
Watch this video
(first part of video is with a tune, last part is stock settings)
My throttlebody AFTER a tune is barely any better than that.

The is a reason why throttle body responds as normal above 3k RPM, but with a several second delay below that. It is NOT functioning correctly, the truck is nearly undrivable by anyone else untill they have had several failed starts (if you try to leave a stoplight like a normal vehicle, you will stall EVERY TIME. The engine will not leave idle if you try to drive like normal.)

I agree Silentbravo, having a manual does make it worse. But as stated, there is no reason it should be any different than a cable AFTER being tuned. None at all.
The sprint booster, from what ive gathered, makes it open further (ex. you give 10% throttle, it jumps to %20 instead to give the feeling of faster response). Magnifies the pedal position i guess. I have researched it before, and it appears a good tune will (in most cases) take care of this issue without needing any piggy back electronics like that. (also not available for 2003)

Thanks for the ideas and suggestions though so far (except GR2017 of course)

Iam sure some would learn to deal with it, but this is horribly irritating to me :evil: :evil:
 

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Discussion Starter · #16 ·
Yeah the tuner has been helpful in trying to diagnose this as well. He is the one who suggested the TAC Module.
The TAC Module is a little silver box on the firewall on the driver side with 2 plugs going to it. Looks like a smaller PCM.

As for the video not working, Iam not sure how to make it work lol. My throttle blade reacts nearly as slow as the youtube video I posted from the trailblazer, if that helps any.

Try this

 

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So yesterday I decided to replace my idler pulley because of a squeak that has developed. In doing that, I had to pull the intake tube off, which is no big deal. After I replaced the pulley, I decided to have the wife work the gas pedal and I watched the plate open and close. I could hear her foot apply the pedal as I directed her to do so, and the plate would move immediately. When I directed her to go from no throttle to wide open, the plate would flip open very fast.
Its possible the motor that moves that plate could be tired on your truck.
 

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Discussion Starter · #18 ·
Bootstrap is your truck all stock as well?
That was my first assumption that the motor was giving out, so I tried another throttlebody on it (although it was another used one) only to see it work just as slow.
The throttlebody I tried seemed to work fine on the other truck it came from, but perhaps it was weak as well.
Thanks for checking that out on yours! I don't know many folks with 03-07 6.0 trucks to compare to here, even being as common as they are.
 

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Discussion Starter · #19 ·
Hooked my scanner up today and slowly applied throttle to make sure the TPS was showing and rising accordingly - it is.
Also, to my supprise, found 3 codes that were not there a few weeks ago.
System Too Lean Bank 1, System too Lean bank 2, and Clutch input Circuit.

The system lean codes make me think intake leak, even though I cant detect one by spraying carb cleaner/brake clean around anything.
Still would not explain the sluggish throttle, but may explain the rough idle when its bitter cold (below 15deg F).
 

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2004 Sierra 3500 6.0L, auto, extended cab, cab&chassis, upgraded to 4wd
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also check your exhaust manifold for missing/broken off bolts. it's common for them to break and air leaking into the exhaust screws up the O2 sensor readings...
 
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