TOPIC: 2000 5.3 Vortec MPG

E89 Octane - Worse mileage. - 3-6% loss below manufacturer suggested mpg.
87 Octane - Good mileage 8-12% above manufacturer suggested mpg.

Doing well considering a 500 lb load.

Hi Don,

My '07 Avalanche is also a 5.3L Vortec, I run strictly 87 Octane (and whatever corn they put in it).

In September when they switched to fuel to their "Winter Blend" my average mpg went from 15 to 13. This is pre-groove. I used every driving trick I knew to coax an extra mile out of a gallon of gas, to no avail.

After I grooved the TB, the ecu was not cooperative at all. Going back into it and making sure the groove was to depth and finished I had some initial successes with mileage but the ecu went back to being stubborn. I rechecked everything and in the midst of the checking I found that the climate control system used the vacuum as part of its controls. Everytime the climate controls cycled I could hear this loud click and with some quick checking realized that it was in fact the climate controls... The manifold vacuum was dropping 2 inches of vacuum everytime it cycled. I shut that off and that is when the ecu started cooperating. Not in a big way but much better than the 13 mpg I was getting pre-groove. local driving now is around 14, highway I did a 250 mile round trip and got 18.5 which was surprising as here in Washington if your trip in one direction is mostly downhill... the return trip is mostly uphill and I was still getting mileage gains.(kinda like everywhere else )

That is where it seems to have stabilized for now. I will be going back into it one more time to update the groove. I will either mod the current TB or new groove the backup TB that I have.

Karl Fortner
Tacoma, Wa.

Hey Karl... I hear you barking Big Dog.

I drove with/against a 40-45 mph gust last night for the test which put me back in the game. *65-68mph and 18.25 mpg results.

**While in 4th gear... 40,45,50,55,60,65mph - very little pedal activity. The On-board comp is very active indeed!

On to my next experience.... Happy Trails All!!!


PDF for 2000-2002 Vortecs 4.8, 5.3, 6.0 (wired throttle)


Don
Omaha Ne.

Hi in sweden we have 98octane and 95 octane gas, I just started to use e85 witch is ethanol, My car is running good, this shuld have even higher octane witch means it burns slower,
Ive just installed some sonic spark plugs gaped at .028 my favorite plugs,
but they work better with gas and when set a little lean.

I hope to do a groove in may on a camper home with tbi, Ill be Back
best wishis for all,

another funny thing going to put some ormus in my gas tank hehe,

Yes, it does burn slower but not necessarily in a good way. The burn reduces the emissions but it does nothing to benefit engine output.

EITHER WAY, THEY ARE TAKING OUR MONEY!

Hi Karl
I have a friend with a 5.3 Liter Avalanche and just a question, you mentioned turning off climate controls did that mean driving without climate control on or disconecting the vaccum line?

Thanks Aaron

Hi Aaron,

I drive with the climate controls off, haven't climbed into the engine compartment yet to find the connection/valve that controls it.

What I do is turn it on set the control setting and then shut it off. This seets all the air gates to a fixed position until I decide to change it.

Karl Fortner
Tacoma, Wa.

The Climate Control Systems almost universally use vacuum to power the switching of the baffles. It is in the switching and diaphragms in control of the switching where the failures occur.

The reason we are concerned with this as Gadgetmen is because these systems develop leaks within the first few years of operation. This is the most commonly overlooked area for vacuum leaks. In fact, it is where I suspect the Suburban class is weakest, as the pick-up trucks in that class show profound gains while the Suburbans give little.

Nevertheless, the system must be checked if gains are not happening, and recommended even if the gains ARE occurring to give the greatest possible gains.

All diaphrams connected to the intake systems are suspect. In fact, EVERYTHING attached to the intake manifold is suspect! If you're not checking EVERYTHING then you are leaving an opening that will inevitably leave you scratching your head wondering what went wrong with a mod.

So, buckle down and get on with the testing. After all, all you're doing is testing. If there's no problem, then you can go on knowing you did the best you could.

If not...

Well, good luck!

Ron

I will have to ask my friend if he would be okay with operating his controls that way and get the groove done. A vaccum pump would fix that problem (with I think there was one in maybe the 70s chev era not sure)

Aaron

Of course the vacuum leaks also explains why I'm getting moisture on the inside of the glass.

I'm getting a vacuum drop of two inches when the system is active, so along with that vacuum leak I'm getting a 'warm air' leak when I shut down creating the environment for the internal condensation on the windows.

Think I will o my own checks on the system and give GM an opportunity to repair it 'under warranty'.

Karl Fortner
Tacoma, Wa.

I'm curious to about the climate control stuff

Hi Karl, this is TracyG in Reno NV. I have someone who just bought an 06 Avalanche w/ 5.3 in it. Is there anything special to know about Grooving one of these. Example is the computer relearn same as others,i.e., did you just disconnect both batt. cables connect 'em and turn key on for awhile to dump memory? I know these are drive by wire, haven't done that kind yet. any info you might share is appreciated! Thanks, TracyG