Vortec 6.0 Drive-By-Wire help

dakota62 · March 24, 2004

Hello, I Purchased my GMC Seirra 1500HD 6.0 Vortec a year ago and now have 10,000 miles on it.

A few months ago I was taking a trip to Texas pulling my trailer when I started to notice a loud sucking noise comming from the throttle body whenever I give it gas and my gas mileage dropped tremenously, I have checked everything I can and I finally called the service department to ask if they have heard of this, they informed me that they are starting to see alot of the drive-by-wire 6.0 vortecs with this problem, and they have no fix for it yet, He seamed to think the problem was the way air travels through the intake, so I installed a Helix Powertower to see if it helped, But it didnt, I have searched the internet for countless hours trying to find any info I can but have had no luck, Does anyone here know of any information at all that will help me fix this problem, or to know when the dealers have a fix or a recall, or just any info that might help ease the pain, I am getting 13 MPG without any load and when I pull my trailer it is down to 7 MPG, gas is too exspensive for it.

thanks in advance

David

Butch 02 Denali · March 25, 2004

That's pretty weird. I have the DBW in my 2002 Sierra Denali and have had no problems with it. I am in a group of over 200 Sierra Denali and GMC C3 owners (the first truck to use it) and not one person has had this problem. The throttle body is nothing more than a simple air valve, there is nothing magic there. Just because the valve is opened by a motor instead of a throttle cable really has nothing to do with it. If you hear a new sucking sound, air is getting in somewhere it shouldn't, and the engine should speed up.

I would look first at the intake tube between the throttle body and the Mafs, I would bet it has a hole or crack in it!

My honest opinion is the dealer doesn't know what they are doing and i would try a different dealer.

Hope that helps, let us know!

Butch 02 Sierra Denali

dakota62 · March 25, 2004

Thanks for your reply, I have talked to 4 dealers in my area and they all say the same thing, And they also seamed to imply that the Vortec 6.0 was the only ones being infected, is that what you have?

I have inspected the throttle body and noticed that the noise is comming from the bottom of the butterfly just as it begins to open, like it is not opening quick enough, also I forgot to mention that the check engine light does not come on, nor does it give any other sign of trouble.

thanks again

mikez · March 25, 2004

I have the same issues that you are describing and I have a 2003 5.3L 1/2 ton ECSB Z71. Gas mileage is about what you are describing. I had a 2000 ECSB Z71 with a 5.3L also and it averaged about 2-3 mpg better. It had a cable actuated throttle body and also seemed to have more power. I'm not so sure about the electronic throttle bodies. I'm beginning to think that they have a flaw to them. Also now I'm beginning to experience surging at partial throttle. My truck now has about 11,000 mi.

Butch 02 Denali · March 25, 2004

Dakota62, yes mine is a 6.0. All Sierra Denali's and GMC C3's are 6.0 with drive by wire. I have had 3 of these throttle bodies off, one my own, to port and polish them for friends. As I said before, there is no magic part here. It is a simple air valve. The speed it opens really doesn't matter, you could push down slower on the pedal and make it open slow too. I am doing a buddies 03 Sierra Denali throttle body porting and polishing this weekend. I will look to see if there are any differences between it and my 2002, but I don't think so. I would still check that intake tube for leaks. Clean your MAFS too, that is something that the dealers never do and it is a common problem that will affect running and fuel economy.

Mikez, clean yours too, and clean any carbon buildup in the throttle body too. Another common problem that will cause your problems.

Butch 02 Sierra Denali

dakota62 · March 26, 2004

Butch 02 Denali

I checked for leaks and found nothing, I also cleaned the MAFS but still have the same problem, As few a miles that are on this thing, everything looks brand new, I ordered a hypertech programmer that will be in tomorrow, I hope it might help fix the problem, I will say that the sucking noise was reduced with the powertower I installed, but I can still feel power loss on take off and if I floor it when the exhuast is facing a wall I can here it sputtering when under a load, also when I ordered the programmer I noticed that your truck does not use the same one, so maybe our computers are different?

thanks again

david

Butch 02 Denali · March 26, 2004

David,

I did have a Hypertech in this truck about a year and a half ago. Our factory computer programs are different, mine is a 325HP 87 octane program, and yours is the 300HP 87 octane program, but our engines are identical, I've compared every part number in them! I wasn't aware they now have a program just for the Denali's, Ill have to check that out!

The sputtering you hear under load is the torque management pulling timing back when you "abuse" it by flooring it! I suppose it could be a computer problem, but I don't think the hypertech will help because Hypertech's don't remove any of the torque management like some of the other handheld tuners and the custom programs do. Make sure you can return it if it doesn't help!

That sucking noise still bothers me, or the fact that it just started does. I still think it's a leak somewhere. maybe something really unusual like a blown TB gasket or a cracked intake manifold or something strange like that. Not trying to scare you, but I have had many of these apart and they are pretty simple mechanical components, not allot to go wrong in them.

keep me informed, this one really has my interest up!

Butch 02 Sierra Denali

dakota62 · March 26, 2004

Thanks, and I will keep you informed, I am not "New Technology" smart, but I am very machanicly inclined, and it seams to me that whatever tells the throttle body to open is just slightly delayed, therefor causeing the loud sucking noise, but I have no Idea what controls it.

I did check the TB gasket when I had it off to install the Helix, and it was fine, but you could be correct about the intake, I noticed it was made from plastic, I would think it could warp very easily.

citydriver · March 26, 2004

Has any1 put a vacuum gauge on it?? Try that and check for crisp movement while some1 stomps the throttle....This may sound weird to you,but it almost sounds like an exhaust restriction to me...bad converters maybe..I know it sounds like for that to happen on a newer truck,but I've seen it happen B4

dakota62 · March 26, 2004

Ok, Guys, here is where I am at.

Before I got the hypertech programmer today I was messing with the TB butterfly while the truck was running, I wish I hadnt done that, because it made the truck run like crap and then died and took me 5 minutes to get it started again, once I got it running like it did before I jacked with it, I went to O'reillys and picked up the programmer, and read all the instructions.

It found 3 DTC's and think I might have caused them when I messed with the TB, but here are the codes: P0102, P0443, and P1515

I reset the DTC's and did not change any programming, but the truck still ran the same, and I could still here sputtering when against a wall, so then I hooked the programmer back up and found no DTC's. So I went ahead with the Hypertech Tuning and now my truck runs fine, no more sputtering and I dont notice the loud sucking noise anymore, and I noticed an increase in power, I will let you know if the gas milage increases, but for now I am happy, let me know what you think.

thanks again

david