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Chevrolet Suburban Active Fuel Management

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

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#6 of 26 Re: Active Fuel Management (Smooth to Rough) [snidebj] by jerrywimer Apr 27, 2007 (4:29 am)
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! Replies to this message: snidebj (May 10, 2007 12:20 pm) jerrywimer (May 11, 2007 3:15 am)
#7 of 26 Re: Active Fuel Management (Smooth to Rough) [jerrywimer] by snidebj May 10, 2007 (12:20 pm)
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. Replies to this message: jerrywimer (May 11, 2007 3:15 am)
#8 of 26 Re: Active Fuel Management (Smooth to Rough) [snidebj] by jerrywimer May 11, 2007 (3:15 am)
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)
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 !!! Replies to this message: snidebj (Jun 10, 2007 4:49 pm) jcurtis72 (Oct 09, 2007 6:29 am)
#10 of 26 Re: Active Fuel Management transition on 5.3L just as bad! [ceemme] by snidebj Jun 10, 2007 (4:49 pm)
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. Replies to this message: jcurtis72 (Oct 09, 2007 6:29 am)
#11 of 26 Re: Active Fuel Management transition on 5.3L just as bad! [snidebj] by jcurtis72 Oct 09, 2007 (6:29 am)
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)
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? Replies to this message: kiawah (Dec 24, 2007 10:38 am)
#13 of 26 Re: Active Fuel Management 4 cyl mode will not stay engaged [mariond] by kiawah Dec 24, 2007 (10:38 am)
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)
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.
#15 of 26 Getting 4 cylinder mode to engage longer by msfoster May 05, 2008 (9:03 pm)
When I took mine (2007 Suburban LT1, 5.3 flex-fuel) into the Chevrolet dealer with the complaint it won't stay in four cylinder mode I was told the engine and computer learn the driver's style and adjusts to the driver. It takes about 500 miles for this learning to complete.   I have had my Sub since December 2007 and have been varying my driving style to figure out what gets best mileage and turns out I wasn't doing myself a favor. The vehicle couldn't figure out the nut behind the wheel. So I took a 250 mile trip, and drove to Seattle. Normally I pride myself in maintaining speed for hills and anything else. On this trip I decided not to exceed 65 miles an hour and allow the vehicle to slow down as much as ten miles an hour for grades. This took some patience since I'm normally one of the left lane guys that passes most traffic, being passed by most traffic was different. The trip to Seattle resulted in 19 mpgs including city driving in Seattle (steep hills). Without the Seattle driving I expect I was getting 20 mpg on the freeway. A previous trip to Seattle in December I had 16 mpg but the engine had less than 1000 miles on it too. Since this gentle driving trip the 4 mpg mode now stays engaged as much as I would like it too. I've gone from an easy 13 mpg in town to 15 mpg. Bottom line keeping one's foot out of it gets the best mileage but it takes a while to notice it because of the computer's learning the driver's style. Now that I've 'programmed' mine I can have fun and get on it every once and a while and it doesn't permanently tank the mileage.

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