Poor Throttle response

[alpapale]

Hi Guys,

My first post. I have a new '05 Silverado LS extended cab with the 5.3L (aluminum block) motor, supposed to produce 310HP. The truck came with the 3:46 differential, which I thought would help with the gas mileage and with the 310 HP, I figured it would still be OK as far as acceleration.

Most of the time, the truck moves OK, especially if I'm already doing 25-35 mph when I hit the gas. However, there are times when the throttle response sucks! It seems especially bad when I'm starting at a light behind several cars so I have to go slow (the truck just drops casually into 2nd gear) then when I hit the gas, the truck doesn't know what to do. If I press the throttle a little harder, nothing happens, a little harder, still nothing, a little more, and then it kits down, and takes off like a bat out of hell. If it's wet out, it'll spin the tires (both w/ the locking rear). This also happens if I start out slowly onto a hill, going slowly through first, again after it just shifts into second, if I call for gas to hit the hill, it seems like the truck falls on it's face until I hit it hard enough and then, again, it kicks down and goes like hell. Seems to me in general it should be a lot more responsive than it is. BTW, no check engine lights, idles perfect and again if I'm already on the highway tooling along it seems ok. Any ideas? I already spoke to the dealer and he said no engine light, no codes, and no fix. Is that true?

The only other hint is that it just seems to be worse on hot days (in the 88 degrees +) , and it also seems to happen a lot after I come off the main road and after turning onto a side road ...when I Hit the gas it goes through this "lethargic thing".

Thanks for any ideas or comments,

Al

[jethro_3]

Welcome to the world of "PCM programmed for the mass market of SUV/Truck buyers." GM starts with a soft shift, abuse mode on, no response program. Until you get a custom tune, Nelson, you will not know what responsive means. Allen can customize your PCM for your needs, MPG, Tow/Haul, or Performance and make the shifts like you want while changing the torque management program to let you get the HP out of the truck that you ask for. What you have now is a truck to fit the average driver, get the PCM to match you with a personal tune. Email me if you want to know more.

[BlenderWizard]

These trucks have what's called "abuse mode" in the computer, which KILLS your timing if you give it hard throttle from a dead stop. http://www.gmfullsize.com/forum/showthread.php?t=29148
Scroll down to the 4th post on the page to see a nice graphic of what abuse mode does, but go ahead and read the whole post there. The only cure for this is to get your pcm retuned by someone reputable, Allen Nelson http://www.nelsonperformance.com

[alpapale]

Hey- Thanks for the input. The problem I have is that this truck has been obtained via a "smart buy" and I will potentially have to return at the end of the term, unless I buy it then. Is the re-tuning reversable ? Can the dealer tell and if so does it effect the warrantee ?

What about the hypertech tuners I've read about ?

Thanks !

[jethro_3]

The tune can be undone and does not affect the warrenty.

Hypercr@# only goes so far, Nelson goes all the way....

[BlenderWizard]

Yeah, all that has to be done is for the dealer to re-flash the PCM, and it is totally back to stock. Hypertech costs nearly as much as a Nelson tune, but doesn't do nearly as much. Jethro, you and I should be on Allen's payroll

[jethro_3]

Consulting fees??? People have no idea what that tune can do and still be within the manufacturers parameters.

[alpapale]

Blenderwizard,

Thanks for the reference. The graph in the post you referred me to really hit home. I like graphs, data, etc. (I'm an engineer) but one thing that was mentioned was that the "abuse control" occurs in first gear only, my problem seems to be mostly in low RPM's in second gear. Granted if I floor it from a stop, it doesn't light up the tires, but the thing that really bothers me is the throttle response when I'm just trying to climb a hill with moderate speed. As mentioned it seems I have to keep pushing down the throttle more and more until something happens, and when it does, it's a hard shift down and the truck takes off. I just want a little kick, seems I have nothing or a violent acceleration, nothing in between. I would totally buy this "abuse control" thing if it wasn't limited to first gear.

[jethro_3]

What Nelson also does is change the shift points and the time it takes to shift up or down. The PCM is programmed for a 1 second shift and that equals friction and heat. Nelson changes that to .1 second and that keeps the trans alive longer and gets down to business not a vacation waiting for it. Also the line pressures in the trans get a change so the shift gets done faster firmer. Not a slam but not that long delay you currently experience. My truck came alive in the shifting alone due to the shift timing change. I gained almost 2 mpg and now the truck shifts when I want how I want with no delay. I asked for mpg first and performance second and got a big helping of both. Blenderwizard got his tune after mine and we both can't say enough about the customer service and the results of the tune. Well worth the money for me.

[alpapale]

Jethro 3,

What you said about shifting would certainally help. It seems if my truck would downshift to first normally without me having to floor the throttle it would help in my particular situation. It seems once it shifts into second, it doesn't like going back down to first even if I approcah a hill, push the thottle or what ever, unless I nearly floor it.

So this PCM alters the up-shift points, I gather you're saying it also changes the down shift points....so now all I need is an extra few hundred bucks!

Thanks for the response guys!

[BlenderWizard]

Originally Posted by alpapale

Jethro 3,

What you said about shifting would certainally help. It seems if my truck would downshift to first normally without me having to floor the throttle it would help in my particular situation. It seems once it shifts into second, it doesn't like going back down to first even if I approcah a hill, push the thottle or what ever, unless I nearly floor it.

So this PCM alters the up-shift points, I gather you're saying it also changes the down shift points....so now all I need is an extra few hundred bucks!

Thanks for the response guys!

Yeah, that was another problem of mine that I brought to Allen's attention: there was a horrible "lag" if I was out cruising between when I would step on the gas and when the truck actually did something. He told me that for whatever reason, GM puts a .7 second (I know that doesn't sound like much) downshift delay on the tranny. That means there is .7 seconds between when you step on the gas and when your truck responds to it. What he told me he suggests is removing .5 seconds off of that delay time, which leaves it set at .2 seconds. Again, I know that doesn't sound like much, but it makes a world of difference as far as driveability goes.

[sportin83]

how can you get this tune if you cant take your truck to him? does he send you a new pcm? what all is involved in installing this? does any one rememeber ruff price? i know these ?'s are asked daily but i forgot and am to lazy to go through all the threads about this. thanks guys

[jeverett]

You tell him what mods you currently have, and the the performance you want (higher mileage, or haul ass) and he sends you a programmed PCM based on what you and him decided on. If you change something in the fiture, holler at him and he'll send you another tune, you just pay shipping. My 93 octane tune is just ungodly awsome. I just can't afford to fill up at 2.60/gal anymore, so I'm lowering mine to an 87 octane for now. Im more concerned about mileage for the time being.

[alpapale]

So do you simply keep then keep the original PCM (I assume its a chip) and switch back if you want to, or if you want to trade/ sell the car or turn in back in as in a lease ?

[bigbadram51]

Originally Posted by alpapale

So do you simply keep then keep the original PCM (I assume its a chip) and switch back if you want to, or if you want to trade/ sell the car or turn in back in as in a lease ?

No he will send you a pcm in the mail, tuned to your specs. You install the new one mail the old one to him. there is a core charge that is returned to you when he gets your old one back. I suppose you could switch it back, but i dont see why you would bother, the dealer wouldnt know. They would just sell it as a extra fast silvy.

Blender, jethro, jeverett and myself are obviously nuts about our tune and cant imagine anything else. You will drive that tuned truck for the first time and wonder where all that power came from. And after about 500 miles where the timing table figures out the new parameters you pickup will be rocket