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2007/2008 Silverado and Sierra Active Fuel Management Problems

106 messages,  Last post on Sep 01, 2009 at 9:04 PM

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What is this discussion about? GMC Sierra 1500, Chevrolet Silverado 1500, Fuel System, Truck


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#23 of 106
Re: 2007/2008 Sierra Active Fuel Management Problems [1offroader] by natesms
Jan 21, 2008 (10:27 am)
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Replying to: 1offroader (Jan 21, 2008 9:32 am)

1offroader,
 
Do you have the 4.10 gears in yours? I know there is a package that has the 6.0 with the 3.73's. The Max package puts in the 4.10's. I turn about 2300 RPM at 70mph. The 5.3 with 3.73s I test drove turned 1900 - 2000 at 70mph.
 
I must say that aside from feeling the AFM kick on and off (my passengers don't notice it like I do, I think it has a lot to do with how closely I am paying attention to everything in my new truck), I really do like driving it around. I think if you want to tow an 8,000 pound boat comfortably you just have to accept paying the price at the pump, or pay the price on the sticker and get the diesel.
 
natesms
#24 of 106
Re: 2007/2008 Sierra Active Fuel Management Problems [ponch1] by mule4
Jan 21, 2008 (1:03 pm)
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Replying to: ponch1 (Jan 21, 2008 10:07 am)

ponch1 I was a die hard gm, ford & dodge owner. Wouldn"t look at anything different.I had all kinds of problems with a new gm car & new truck.All they would say was all the problems were normal. knowing they were lieing.I own a truck now that gets 18.5 to 19.5 on freeway 70 mpg with cruise set & depends how strong wind is.It doesn"t have AFM.It has 381 hp 6 spd. trans.It will pull a 9500# trailer like a 3/4 ton but my tk. is 1/2 ton.I had one problem with it They fixed it with no problen at all.Great service dept.Good luck with your new truck.I have had with mine
#25 of 106
Re: 2007/2008 Sierra Active Fuel Management Problems [1offroader] by sknabt
Jan 21, 2008 (5:45 pm)
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Replying to: 1offroader (Jan 21, 2008 9:32 am)

"I do not understand where all the lousy mpg is coming from. I get an honest 18 on the fwy. at 70 mph, in cruise control. Maybe that is the key, having it on cruise control." - 1offroader
 
I agree 100%.
 
Don't own a 6L but I do own an '08 5.3L Sierra. Overall city/highway I'm up to 17.2 mpg. To get there I have to liberally use the cruise control. Don't do 70. Tend to set it to 65 and forget it. I even use cruise control around town when I know I'll be able to tool down the road a couple of miles.
 
Even mild acceleration sets it to V8 mode. I find my foot on the petal isn't as efficient as the cruise control going up inclines and maintaining speed. On flats cruise control spends the majority of the time in V4 mode. Naturally, when going down even gentle grades cruise or no cruise you'll get great mpg in V4.
 
I haven't reset the command control to see how much I get just on the highway but looking at the instant fuel economy display I'd estimate 19-21 mpg.
 
The downside is around town going stoplight to stoplight it's hard to get decent gas mileage. I tend to press the petal briefly to maintain speed then drift a bit, etc. But it depends on traffic.
#26 of 106
mileage by chainlink
Jan 31, 2008 (3:24 pm)
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Good Lord: all these probs with the afm in these new mod has convinced me jus to put a new block in mine when she's done. I have the 99 new body z\71 4x4 and have loved every minute behind the wheel,with almost 300 thou she has been without a doubt the best truck I have ever owned.3 foot of mud or flat out like a lizzard she performs like a dream,and at a mer $2,3000.yep a new 5.3 block is in my future.
#27 of 106
Re: 2007/2008 Sierra Active Fuel Management Problems [natesms] by 1offroader
Jan 31, 2008 (8:29 pm)
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Replying to: natesms (Jan 21, 2008 10:27 am)

natesms
I have the 3.73 gears, and 6.0L. I am not towing a huge trailer or boat and don't need the 4.10s. Yes, the Max Trailering package has the 4.10s.
1offroader
#28 of 106
Re: mileage [chainlink] by 1offroader
Jan 31, 2008 (8:35 pm)
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Replying to: chainlink (Jan 31, 2008 3:24 pm)

chainlink
Chevy has sold perhaps 100,000 Silverados with AFM and there are what, 27 posts about problems??? And several of those posts have been by the same person. Do you consider that a sign of a major problem?
 
I'm sure you've got a fine truck but I don't think 27 posts is excessive considering the tiny fraction of 1% with problems, do you? If there was a vehicle out there that sold 100,000 units and there were 100 problems (0.1 %) would you not buy it?
 
1offroader
#29 of 106
Re: mileage [1offroader] by natesms
Feb 01, 2008 (8:30 am)
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Replying to: 1offroader (Jan 31, 2008 8:35 pm)

I agree with 1offroader. Given the volume sold and the small number of posts I think overall most poeple are happy with their purchase. Even with all the talk about how great the Toyota's are, if you look through that forum there is gripping going on there as well. I was amazed to see there were multiple people reporting getting the motors replaced due to "loud knocking engine noise".
 
I'm getting used to the AFM "kick" and don't really notice it that much anymore. I'm also averaging 12.5 in the city now, which given rounding and factoring in that is very cold and remote start has made my list of top 5 best things ever, is excatly what the window says.
 
I have a 550 mile trip this weekend. I'll reset the average and let you all know what I get at highway speeds. I don't believe I have the will power to not do at least 5 over the speed limit so I expect it to be pretty crappy at 75 mph.
 
Another question pertaining to fuel mileage. Does anyone know if you get worse milage when you have the 4X4 set to auto (assuming it isn't engaged all the time)? I can hear something moving when you switch it to that mode, so I'm assuming that you are turning more "stuff" and hence decreased milage.
#30 of 106
Re: mileage [1offroader] by mule4
Feb 03, 2008 (5:39 pm)
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Replying to: 1offroader (Jan 31, 2008 8:35 pm)

About the small number of posts about the problems don't mean anything. The larger number of people don't post on these forums. lots of people that have trouble with their trucks have been told it's normal & they believe it .
#31 of 106
Re: mileage [1offroader] by gaspasser2
Feb 03, 2008 (7:52 pm)
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Replying to: 1offroader (Jan 31, 2008 8:35 pm)

I doubt 100,000 owners are even aware of this forum. Just my .02. But I do hope its not as bad as you said.
#32 of 106
Re: mileage [natesms] by natesms
Feb 04, 2008 (8:46 am)
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Replying to: natesms (Feb 01, 2008 8:30 am)

Did my trip this weekend. I averaged out to 16.3. It got about 15.8 on the freeway doing 70 - 75 on cruise control (pretty flat road going down I70 in Missouri), and then increased when I hit 60 MPH roads. That actually surprised me as about 55 miles of road is quite hilly with lots of curves and it handled it very well. I also drove like I was trailering something allowing my speed to increase going down hills and slow down going up, this kept it in v4 mode a good portion of the time. I think if I would back it off to 60 on the highway I could get the advertised 17.
 
I do feel that GM has misrepresented the milage some though, seeing that even on my best driving behavior I can't get the stickered milage in either the city or the highway.
 
I'll be taking it in this week to get it looked at though. As others have stated in prior posts, it feels like the motor is tugging going up hills and the transmission seems to hunt for gears to often. I've got 1300 miles on it now. If it can't figure out when it should shift in 1300 miles, then something is wrong. I'll be interested to see if I get the "It could take up to 7,000 miles" line that someone else received.

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