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Sluggish Acceleration At Slow Speeds

B

Bruno

SM 2003
Full Member
Joined
Aug 14, 2002
Messages
951
Location
Katy, Texas
My Av drives nice except low speed acceleration. An example, tonight I was coming to a light slowing down applying a light brake. I notice that the right lane is clear so I veer right and press the accelerator 1/2 way to the floor. The response is almost a stall until the trans downshifts and then I am off at a normal acceleration, but the pause is scary. It reminds me of when you drive a manual transmission and try to accelerate from a near stop and the engine just lugs down. :9:

Now is this what you all experience with an unmodded engine? ???
 
I'm not really impressed with the response I get when I really set my foot down either. I've driven a Volvo 850 turbo for the last few years and when the foot went down, the head went back! I knew though that when I bought a truck I wasn't going to be getting that response unless I did some modding. I think after I get the majority of the superficial mods done (i.e. painting cladding, escalade gauges, ect.) then I'll try under the hood. I don't have alot of confidence when it comes to that yet ;)
 
It all depends on what you are looking for in a vehicle.

The Avalanche still has relatively snappy acceleration. Keep in mind you are dealing with a 6,000 lbs vehicle whereas two or three people can move an import around by hand. Yes, imports have smaller engines, but usually not relative to vehicle size and weight; their output power is usually more per pound than the Avalanche.

The Avalanche is good at what it is made to do. It is not trying to be a racecar.
 
I read an earlier post about putting the vehilce in Tow/Haul mode in order to get more bottom end out of it. I have done this a few times and do notice a difference in the shifting.
 
I have completed some peformance mods, and am still hoping that the Superchips mod will improve acceleration.... especially in the area which you are experience some disappointment. My take is that the shift points are not "performance friendly" which causes the engine to work real hard to get the beast moving without a downshift. There's also been some discussion about the power-robbing effect of the torque management system at lower speeds. Tow/Haul helps this... and being able to choose your shift points with a Hypertech or other performance tuner should help greatly as well. Here's hoping anyway!! ;)

-------Bow:B:tie
 
You should find in tow/haul that at speeds under 60, the throttle response feels better as you tend to run higher RPMs in each gear. For example, when I leave work in the afternoon, the highways aren't too backed up but you do go about 40-60 for the first couple miles before it really opens up. In TH mode, you press down and it really lunges. Heck, at 40-50 you might still be in 2nd gear!

Jamie
 
I have noticed the sluggishness at lower speeds as well. I am working with a company that makes custom chips and programs for vehciles. What they are saying may be happening is that the vehicle is getting too much gas at the lower speeds or at a dead stop, so the motor is not able to burn all of it efficiently. What they are proposing on doing is leaning out the air/fuel mixture in the appropriate low speed/rpm ranges. Essentially the end result is better gas mileage, more power and acceleration.

The cost for getting all of this done is about $1200, sooo...as this develops, I'll keep everyone posted. It all a matter of cash flow at this point.
 
Lightning said:
What they are saying may be happening is that the vehicle is getting too much gas at the lower speeds or at a dead stop, so the motor is not able to burn all of it efficiently.
Click to expand...

Yeah that is what it feels like almost like the engine is flooding out, then it shifts down and away we go...

I started this thread not to discuss Av acceleration vs other vehicles, but to see if my experience was common to the Av with the 5.3. It appears that it is and I will just have to do the FIPK and exhaust mods to see if this helps.
 
The lack of a punch when accelarating from 20 mph was the first thing that I noticed when we switched from our 99 Silverado to the AV. We had the same engine with 15hp less and it was a 4x4 ext cab. I was very dissapointed and I put that on the extra weight but the engineers have certainly played with the electronic box and it might be just a matter of using a 99 black box, this mod should not be too expensive.
 
Bruno said:
Yeah that is what it feels like almost like the engine is flooding out, then it shifts down and away we go...

I started this thread not to discuss Av acceleration vs other vehicles, but to see if my experience was common to the Av with the 5.3. ?It appears that it is and I will just have to do the FIPK and exhaust mods to see if this helps.
Click to expand...

I have done these mods on my AV and it does not solve the problem. All these mods have done is give me a little better throttle response and better power in the higher rpm ranges.
 
I completely agree with Lightning. All I have done so far is work on the air intake / exhaust and althought I love what it has done for the most part it did not improve acceleration.

I'm not much of a racer but when I have tried to show off I've been embarassed a couple of times. I don't think it's a weight problem so hopefully a program will fix this.
 
I tried to stomp on the gas a few times as well, but found just what everyone else has been saying to be true...the Av will downshift and race the engine but you just won't go anywhere....what I found to work best for me is to just accelerate to the point where the AV won't downshift....it seems to move briskly along.....I also have the basic performance mods and they seem to work better in the higher rpm range and at highway speeds..... :B:
 
NJAV said:
I tried to stomp on the gas a few times as well, but found just what everyone else has been saying to be true...the Av will downshift and race the engine but you just won't go anywhere....what I found to work best for me is to just accelerate to the point where the AV won't downshift....it seems to move briskly along.....I also have the basic performance mods and they seem to work better in the higher rpm range and at highway speeds..... :B:
Click to expand...


This is the only thing that disappoints me with the Av. It is a great vehicle but I worry about the responsiveness when I need to get out of the way of the idiot drivers in my intercity driving. My '99 Tahoe has the 5.7 and has good acceleration at low speeds so I have some attitude adjusting on my part. When I punched it, I was gone.
 
I've noticed a bit of sluggishness a few times, but I remind myself I'm humping 6,000 lbs. of AV and I goose it a little more and she takes off. I'm not looking for the same performance I expect from my Z28. >:D It's a heavy truck that performs like one.

Truckman :B:
 
I think a lot of this has to do with the torque management system, the 3:73 gearing and the AV's weight. ?I have added a cat back dual exhaust systems and Volant cold air induction kit that has helped but more so when the RPMs are over 2,000.

I'd like to report on the results of my Superchips install but it crashed and they're checking out the tuner. ?I was hoping it would help with the TM issue. I plan on upgrading to the 4:10 gearing and think that will help the most.

Check the site, lots of good info already listed that can help you. ?
 
I have built and raced cars for many years. After my long drive in my Avalanche, I am looking for just the opposite of what I want in a race car. I want more torque at 2000 - 2800 RPM. I would gladly give up the 5000 RPM power for more pulling power at the 65 MPH tow spot. Most of the power mods, like cool air and opened exhaust have their effect at higher speeds. Even with the 4.11s, is needs just a bit more - say 25 ft lbs at 2200 RPM. Anybody who tows knows what I mean. If a custom chip is burned for the 1500 Avvy, that should be the goal. - Sethracer
 
I have also noticed this problem.. also have installed a cat back system and a FIPK.. and a MAF sensior...still not happy with the low end..

If anyone that has installed a programer can say they have inproved the low end..I will program ASAP
 
I've noticed this as well, especially if the rpm range is right where it wont downshift. I had a 1998 K1500, Z71 pickup before the AV with a 350 and it seemed to have more low end grunt even though the numbers on the new motor are better. I did the airbox and exhaust on the 350 and it really made a difference, I hope it does the same when I do the AV.
 
You may want to try MSD ignition. 6A is about $ 179.00 from summit. Anyone have any experience with MSD on their AV?
 
I've used MSD products on other small block applications with great success. I havn't seen any indication yet though that the stock set-up is lacking however.
 
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