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Chevrolet Suburban Active Fuel Management

26 messages,  Last post on Jul 11, 2008 at 11:56 PM

You are in the Chevrolet Suburban & Tahoe Forum. Your Hosts are steve_ & tidester

What is this discussion about? Chevrolet Suburban, Fuel System, SUV


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#5 of 26
Re: Active Fuel Management (Smooth to Rough) [jerrywimer] by snidebj
Apr 26, 2007 (4:31 pm)
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Replying to: jerrywimer (Apr 25, 2007 3:26 am)

Thanks for the replies and just an update:
Apparently this AFM system is getting alot of attention with the "reportedly seamless" transition between V8 and V4 mode. Mine is not seamless with the 6.0 liter. Far from it! Plus there are others out there like wjith the same symtoms. Most would like or are requesting to disable the AFM.
 
I had my 6.0 liter Avalanche at the dealer and they report that its in normal operating conditions! Hard to believe but..........if GM has designed this "AFM" to have operating conditions such as what I have, then they have some serious engineering problems. Besides, my neighbor has the 5.3 liter and we took them down together. His engine operates as bad or worse than mine.
 
The dealer took 2 Avalanches off the lot and they operated smooth as silk! Big margin for "normal operating conditions".
#6 of 26
Re: Active Fuel Management (Smooth to Rough) [snidebj] by jerrywimer
Apr 27, 2007 (4:29 am)
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Replying to: snidebj (Apr 26, 2007 4:31 pm)

I'm afraid that "operating normally" is the service department code phrase for "it's different but we can't find anything to change that would address it". I can't feel my Av changing from one to the other (well, maybe, if it's an extremely smooth stretch of road, but just barely even then). And prior to changing out my factory exhaust to the GM Performance Parts "Touring" exhaust system, I couldn't hear a difference either. With the new louder exhaust I can tell the difference, though most folks who don't live with it daily wouldn't realize that the change in tone is because it's in V4 mode- it still sounds like a V8, just a change in the tone from the one produced in V8 mode that's slight but obvious.
 
Sorry you're having problems though. I still suggest looking into getting a PCM tune. Besides the potential power and fuel economy boost (the reasons most everyone else gets the tune), there's the chance that the new tune will reduce or eliminate the switchover to V4, as I said earlier. Since you've got an Avalanche, I highly recommend looking up the Chevy Avalanche Fan Club of North America and its forum (won't link it here, to keep the mods from smacking me around). The one or two experiences with tuning on an 07 that mentioned the AFM being affected were on that site.
 
Good luck!
#7 of 26
Re: Active Fuel Management (Smooth to Rough) [jerrywimer] by snidebj
May 10, 2007 (12:20 pm)
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Replying to: jerrywimer (Apr 27, 2007 4:29 am)

I took my Avalanche back to the dealer again to have them look further into the Active Fuel Management system with the 6.0 liter. After contacting GM tech support there are updates for the computer to smooth out the roughness when it switches from V8 to V4 mode.
The dealership tech and the GM tech loaded in 10 updates to address the situation.
 
Yahooooooooooooo! I would say that after the updates and driving another 500 miles or so, that the AFM switches almost as GM claims as "seamless". Man, am I glad that they got it fixed because it was annoying as hell.
#8 of 26
Re: Active Fuel Management (Smooth to Rough) [snidebj] by jerrywimer
May 11, 2007 (3:15 am)
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Replying to: snidebj (May 10, 2007 12:20 pm)

I'm glad they were able to fix your issue. It sounds like you're 6.0l works much like my 5.3l now.
#9 of 26
Active Fuel Management transition on 5.3L just as bad! by ceemme
May 26, 2007 (6:59 am)
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Hey guys,
 
My 5.3L LT2 acts just the same as Jerry's 6.0L prior to the software updates. However when I took my 2007 Suburban back to the dealership, they tell me that there are no reported problems with AFM and consequently no software updates available. I wear two hearing aids and not only hear the change in the exhaust noise going from 8 (smooth) to 4 (rough), I can feel the vibration in the footfeed.
What to do !!!
#10 of 26
Re: Active Fuel Management transition on 5.3L just as bad! [ceemme] by snidebj
Jun 10, 2007 (4:49 pm)
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Replying to: ceemme (May 26, 2007 6:59 am)

I would say take it to another dealer!! There are at least 8 updates for the "AFM" stumble, lurch, hard shift etc.
The dealership that I dealt with showed me the update numbers that they installed and man it was a BIG difference. GM claimed that the AFM was seamless, but, from new mine had a terrible stumble going between V8 to V4 and back. After the updates its smooth as silk!
Call the GM tech line to have them open a case number for you then take it to your dealer or a dealer and have them ride with you so that they will understand whats happening. I'm also told that there is an update for the 6.0 liters that have a rough idle to them.
#11 of 26
Re: Active Fuel Management transition on 5.3L just as bad! [snidebj] by jcurtis72
Oct 09, 2007 (6:29 am)
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Replying to: snidebj (Jun 10, 2007 4:49 pm)

Mine has the 5.3 with AFM I have the same rough idle problems and jerking going down the road. Total of 8 trips to the dealer now, the last time they changed the torque converter no change. The bad thing is about 75% of the time the AFM works fine, 25% of the time it jerks very hard like a misfire. Each time the dealer has checked for software updates. This is driving me and the dealer nuts!
#12 of 26
Active Fuel Management 4 cyl mode will not stay engaged by mariond
Dec 24, 2007 (9:04 am)
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I have a 2007 suburban with 5.6 engine. It operates fine in all situations other than it will not effectively operate in 4 cyl mode. It shifts into 4 cyl smoothly and I notice no problems nor any hint of roughness, however, it will only hold in 4 cyl mode while going down hill with your foot off the accelerator. It absolutly will not hold in 4 cly mode under any condition otherwise. On an level road at any cruise speed it will instantly switch back to 8 cyl if you ever so slightly touch the gas. I have carried the car to two different dealers and called Chevrolet customer service. The dealers said that they could find nothing wrong with the system's operation. The Chev customer service offered to located another dealer for me to take it to, but otherwise didn't seem to have any solution.
Does anyone have any advice that may help?
#13 of 26
Re: Active Fuel Management 4 cyl mode will not stay engaged [mariond] by kiawah
Dec 24, 2007 (10:38 am)
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Replying to: mariond (Dec 24, 2007 9:04 am)

Have 2007 LTZ Suburban, and it will stay engaged while in 4 cylinder mode on interstate, on level to down hill. Depending on the length of slight upgrade, it may or may not kick in 8cyl. Anything over a short slight upgrade, will go to 8cyl mode. Set the cruise and let it do it's thing. You don't mention your speed, but I would think if you're cruising over mid60's the wind resistance would be enough to need 8 cylinder mode. You should also make sure you are in 2wd mode (not auto mode), and your tires are properly inflated (or on high side), to keep rolling resistance lower.
 
I would also think any use of Ethanol blend gas, containing less energy, would force 8 cyl mode as well. You may want to try shifting to a different brand, to see if that makes any difference.
#14 of 26
Re: Active Fuel Management (Smooth to Rough) [ceemme] by jake55
Mar 27, 2008 (11:06 am)
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Replying to: ceemme (Apr 13, 2007 7:17 am)

Same problem on 07 suburban I am trying to find a way to disable it.
Some say its possible dealer says no. It drives me nuts.

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