Huge Reduction In Performance Sierra 6.2l

[tamimi]

I have a 2010 6.2L V8 GMC sierra 1500 Crew cab short bed.

This monster drives more like super car than a Truck!

 

I noticed a huge reduction in performance when the tank is full. When so, it drives really bad like a V6,

So I did a quick 0-60 test and found 2 seconds difference between a full and less than a quarter tank!

 

I have a 2007 5.3L V8 Tahoe and never felt any difference in performance whether the tank is full or not !

 

 

Any idea what is behind this drop in performance?

[Stevens03]

Mine runs like a sculled dog

[pm26]

This makes no sense. 20 gallons of gas only weighs about 140 lbs, which is the weight of a light passenger. You may have a fuel delivery problem of some kind.

[temmert1]

I agree there is a problem with truck. I notice no difference if full or near empty. Well thats not totally true. My wallet is definately lighter.....lol

[MaverickZ71]

Sounds like an in-tank fuel pickup problem. You might try running a few bottles of Techron fuel system cleaner (the only one recommended by GM and known for helping with this kind of trouble) through it to see if that helps any.

[louie730]

Sounds like an in-tank fuel pickup problem. You might try running a few bottles of Techron fuel system cleaner (the only one recommended by GM and known for helping with this kind of trouble) through it to see if that helps any.

 

 

It is my understanding that in a flex fuel GM truck that when you get a fill up the computer will pull some timing until the system knows what kind of fuel you just put in. You may have put 87 octane, 93 octane or even E85. After the type of fuel is known, the truck will set the computer to the proper timing for the fuel in the tank at that time to protect the engine from knock.

I have noticed this in my truck too. It says in the owner's manual that it takes the computer about 7 miles to adjust.

[Stevens03]

Sounds like an in-tank fuel pickup problem. You might try running a few bottles of Techron fuel system cleaner (the only one recommended by GM and known for helping with this kind of trouble) through it to see if that helps any.

 

 

It is my understanding that in a flex fuel GM truck that when you get a fill up the computer will pull some timing until the system knows what kind of fuel you just put in. You may have put 87 octane, 93 octane or even E85. After the type of fuel is known, the truck will set the computer to the proper timing for the fuel in the tank at that time to protect the engine from knock.

I have noticed this in my truck too. It says in the owner's manual that it takes the computer about 7 miles to adjust.

 

 

Interesting, I've never noticed this... but 99% of the time, I run 93

[jblakeney]

It is my understanding that in a flex fuel GM truck that when you get a fill up the computer will pull some timing until the system knows what kind of fuel you just put in. You may have put 87 octane, 93 octane or even E85. After the type of fuel is known, the truck will set the computer to the proper timing for the fuel in the tank at that time to protect the engine from knock.

I have noticed this in my truck too. It says in the owner's manual that it takes the computer about 7 miles to adjust.

 

What the crap did they do to make it take an adjustment period and what causes it to occur. Change in Fuel Level? A steep incline or decline could cause it to set off..... That does not make sense.

 

The Knock sensor is listening for engine ping, in order to adjust the timing. The old systems could detect the ping and adjust extremely quick. Why would they step back......

 

Seems as if it shouldn't matter...... If anybody knows the logic's of the new system that adjust the timing via the knock spill it.

 

Jbo

[RyanbabZ71]

http://www.gm-trucks.com/forums/index.php?showtopic=78169

[Stevens03]

http://www.gm-trucks.com/forums/index.php?showtopic=78169

 

Learn something new everyday...

[RyanbabZ71]

That info is from 08

[Stevens03]

My previous vmax wasn't flex fuel... so I didn't know...

[2010LTZ4x4]

http://www.gm-trucks.com/forums/index.php?showtopic=78169

That was an excellent article to read. I won't be leaving the key on from now on when i re fuel anymore. (used to like listening to the music)

I can't say i really ever notice a change in peformance though from one fill to the next, but I've been using Ultra94 since day one. The 94 makes a difference in light to light runs with other trucks.

[RyanbabZ71]

If you dont change fuel (go back and forth) you shouldnt really notice a difference. I notice a slight difference if I go from E85 to 93 which I havent done since January.

[tamimi]

Thank you all for your replies..... wasn't expecting this much replies!

 

Great article!

 

I have never used anything but 95E ( yes we have 95 over here ) so its not supposed to take the 8 mile period for readjustment!.

Is there a way to lock this sensor on a specific type of gas? using Diablo Racing Trinity or predator perhaps ?

 

Its really frustrating to know I have to drive 8 miles for my truck to "warmup" thats why I hate Flexfuel ! I believe that any engine with +6L should not run anything but +93E ! and for those who want to save on gas go with the smaller engine and PLEASE DO NOT ruin our joy !