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AFM Question - 2011 Avalanche

EMSDC

Full Member
Joined
Dec 4, 2012
Messages
68
Location
Seaford, DE
I have a 2011 Avalanche with 18000 miles and have the rough idle at stops as others have mention (no service codes). The question I have is while driving in city conditions 0-35 mph with stops, when the AFM shifts downs from 8 to 4 the entire ride of the vehicle changes as in not as smooth when using 8 cylinders. It seems like it really struggles while in the 4 cylinders during city driving.

Anybody in the club have the same?  Maybe it's me, but I sure didn't notice it when I bought it new with 5100 miles!
 
I have a 2011 as well. I can't tell the difference when it shifts to 4 cylinder unless I look at the DIC. The change is totally transparent city, highway or towing. I'm not much help, but know it should ride smooth in 4 or 8 cylinder.
 
If the change is seamless, you must still be running the stock exhaust.  I think it's a pain in the ass, especially at low speeds, don't like it, it feels like a miss.  I'm turning mine off.
 
I was vaguely aware of an idle problem and possible related TSB for the vehicles with AFM.

I took my 2010 in for a late check up with 35,750 miles and the first thing my service guy asked was if I was having a problem with rough idle at freeway off ramps.

Curiously, I responded yes as I had just become aware of this. It was not really pronounced, but more like a fouled plug or something. Sure enough, there was a TSB for this.

Unfortunately, I never discerned if the service performed worked or not as I traded that Avalanche in for the 2013 before the service was finished.

I did drive the 2010 home that night and returned it to the dealer the next morning. I can't say that I noticed the rough idle during the last 20 miles of driving before I picked up the 2013 model. I was in a state of confusion.  :eek:

I don't recall what the work was, but I may still have the service codes for the work they performed. Let me know if you want that information.
 
If the engine was designed for AFM, surely GM built the thing with elements that counter side effects with cylinders shutting off, oil flow, cylinder wear,  cooling impact , etc. All auto manufactures have this technology now so won't all car companies be in the same boat? Will we all see these issues with AFM?  ???
 
Cat Dancer said:
I don't recall what the work was, but I may still have the service codes for the work they performed. Let me know if you want that information.
I would very much like to know what work was done, relating to the TSB.

Since it's a '10, that might have been early enough for the replacement of the oil pan gasket & the PCV system side valve cover, which is one of the fixes for AFM issues.  The gasket incorporates a shield which minimizes the effect of excessive oil spray from the AFM relief valve, during certain driving conditions.

Another possibility would be the replacement of the throttle position sensor, which was an issue on several model years.  GM established a special extended warranty for this condition.

Please, let us know what you find out.  Thanks!

Nick
 
Bassman Z71 said:
Will we all see these issues with AFM?  ???
My personal belief is that AFM is a technology that will be difficult to perfect.  Maybe GM, or one of the other auto manufacturers will prove me wrong.

Something EMSDC said caught my eye.  I wouldn't expect to see a lot of AFM activity between 0-35 MPH, in the city.

Any way you look at it, the exhaust note on AFM-equipped 5.3's sound odd to me, even while idling. A co-worker has an '08 Silverado with a 4.8, and no AFM.  That engine sounds exactly like an LS, should.

So, when I finally turn off my AFM, I expect to hear the same odd exhaust note, while idling - since AFM shouldn't be active, then.

Nick
 
Nick@Night said:
I would very much like to know what work was done, relating to the TSB.

Since it's a '10, that might have been early enough for the replacement of the oil pan gasket & the PCV system side valve cover, which is one of the fixes for AFM issues.  The gasket incorporates a shield which minimizes the effect of excessive oil spray from the AFM relief valve, during certain driving conditions.

Another possibility would be the replacement of the throttle position sensor, which was an issue on several model years.  GM established a special extended warranty for this condition.

Please, let us know what you find out.  Thanks!

Nick

I had some time yesterday to look through the paper work and did not see anything on the work order listing the condition. I'll speak with the service guy in a week or so when I return for paint issues.  ???

I often drive the last 1/2 mile in my neighborhood with a strict 25 mph limit in cruise control. It has activated as low as 23 mph, but typically 25 mph. If the kid activities are non existent, I'll cycle through the DIC and am surprised how much of this drive is on 4 cylinders and very close to idle rpm. I can feel when it jumps back to 8 either from a slight up hill section or when I'm down to 5 mph nearing a stop.

The engine & transmission on the 13 is so smooth, I rarely detect the change at highway speeds.

Road trip coming up on Tuesday. I'll be paying attention for differences from the 2010.

The rough idle issue only manifested a few days before I released the 2010 for the 2013. I suspected a fouled plug or loose wire.
 
Cat Dancer said:
It has activated as low as 23 mph, but typically 25 mph.
Road trip coming up on Tuesday. I'll be paying attention for differences from the 2010.
Have heard that tighter engines, with better compression, will activate earlier & remain in V-4 mode, longer.  Mines an '08 with 70K miles.  Probably a little too late to save my 5.3 from the inevitable, but am going to try, by tuning out AFM.

Cat Dancer said:
The rough idle issue only manifested a few days before I released the 2010 for the 2013. I suspected a fouled plug or loose wire.
I was interested because the dealer seemed to already know what the issue was.  Thanks for looking into it.

Nick
 
Nick@Night said:
Have heard that tighter engines, with better compression, will activate earlier & remain in V-4 mode, longer.  Mines an '08 with 70K miles.  Probably a little too late to save my 5.3 from the inevitable, but am going to try, by tuning out AFM.I was interested because the dealer seemed to already know what the issue was.  Thanks for looking into it.

Nick

I'll press about it. My guy is a very long time friend. I do not recall where I'd heard of this a month or so before, but it was not on this forum.

(Revision/Addition) I'm wondering now if he was speaking out loud as he is aware of my long history with CAFCNA, an Avalanche owner/driver since 03, and I've asked him about 2 other Avalanche drivers CAFCNA members I know of that frequent his new location. He did that when I brought my 2010 Z71 in after the first oil change indicated a rear main seal leak. It was fixed as warranty. This may have been also or they halted this fix when they learned I was about to trade it in for the new one.  ???

The lowest my 2010 would allow cruise control was 24 mph.

I'd be very happy with engine braking while in cruise on long downhill grades. All of my Avalanches have been like Soap Box Derby vehicles while going downhill.  :eek:
 
Nick@Night said:
Was thinking that's where the term Wheeeeeeeeeeeeeeeee started.

It was more like "Please Stop!" even though my pedal was maxed down as far it would go and my eyes were closed more than a few times. I decided a long time ago I did not want to be a witness to my own demise. The 03 was terrible and the 10 was much improved. The 13 is near perfect but it is still breaking in.

I do a lot of mountain driving, some of it via interstates. The rig is great at 85+ but the state and local authorities are just waiting for my lapse in attention.
 
Bassman Z71 said:
If the engine was designed for AFM, surely GM built the thing with elements that counter side effects with cylinders shutting off, oil flow, cylinder wear,  cooling impact , etc. All auto manufactures have this technology now so won't all car companies be in the same boat? Will we all see these issues with AFM?  ???

This be what we call naive. Look up 4/6/8 Caddy engines from the mid '80's. As with those motors, the 5.3 wasn't designed for AFM.  It's a late life retrofit. Other manufacturers, notably Honda, are using this successfully. GM ain't Honda.
 
ltxi said:
This be what we call naive. Look up 4/6/8 Caddy engines from the mid '80's. As with those motors, the 5.3 wasn't designed for AFM.  It's a late life retrofit. Other manufacturers, notably Honda, are using this successfully. GM ain't Honda.

This thought brought up a recollection. Piston Slap

Im not jacking the thread, Honest.

The 03 was doing this from day one and was new to me. I found CAFCNA in July and that was a hot and long discussion. The 2010 had it on occasions as would be expected with cold weather starts or after prolonged resting periods of 5 days or more.

So far with the 2013, I have not detected it. I have only had a few cold weather moments and a few 4+ days between starts. NADA

It doesn't sound like a boat at idle in a marina either.
 
5.3 piston slap started with day one of this small block design update back in '99. First GM denied it existed. Then they said it was normal, which it actually was in a twisted way. Then they reinstated their 50's/60's position that 1K mi/qt oil consumption was perfectly ok for new motors. Then they kinda fixed the piston slap problem but not totally. Then when DOD/AFM was implemented they got some relief as all that cold lifter noise was difficult to discern from piston slap. Then the poor AFM design started biting them in the ass by totally dorking up 1 & 7, which they at first completely denied when it began to first show up as simple excessive oil consumption issues. And then.......

And that's just engines. Wanna talk about brakes??? How 'bout transmissions??

GM has been lost to me for at least a decade. The only reason I bought an Av is because no one else makes one.
 
And what really makes me so cranky is that it didn't usta be this way. I fell in love with the Chevy small block V8 when it first hit the streets in '55. A great bit of design and design execution. Despite GM's worst efforts wrt the 5.3 revision, it lives to this day.
 
ltxi said:
And what really makes me so cranky is that it didn't usta be this way. I fell in love with the Chevy small block V8 when it first hit the streets in '55. A great bit of design and design execution.

I agree 90% of the over 40 vehicles I have owned have been GM, I love the styling and interiors, but too many have lived up to the name "Garbage Motors"

I love my Avy and will probably never part with this one, but the AFM has been a huge pain in the posterior!  
I was lucky to have a great service manager and with the help of this site was able to get every possible TSB done while under warranty.

Now I just have to save a few bucks to get a new tuner to disable AFM.
 
DouglasOak said:
Now I just have to save a few bucks to get a new tuner to disable AFM.
Which way are you leaning on a tune?

Also, I know GM has made some missteps,  but would you rather have a Triton?
 
Nick@Night said:
...  but would you rather have a Triton?

Or a Furd?



 
I currently have an Edge CS programmer, but it does not turn off AFM. I want the DiabloSport inTune handheld tuner.
I really don't want to go custom tune as I want to be able to switch between modes and don't wanna have to buy another ECM to tune and then swap it back with the stocker for winter use or economy mode.
I considered doing an all out performance tune on a separate ECM and keep my stock ECM and Edge programmer but that is way too much money for me to justify to the better half... especially when all my extra cash is supposed to be going into the new bike fund!!!
 
DouglasOak said:
I really don't want to go custom tune as I want to be able to switch between modes and don't wanna have to buy another ECM to tune and then swap it back with the stocker for winter use or economy mode.
Haven't fallen in love with any of the handhelds.  

Module swapping won't really work for the 6-speed, unless you aren't concerned about the TCM. Figure I'll be in one, someday.

Best solution for me is the AutoCal device, but I'd want a tuner that's willing to pick up the phone.  

I half expected for Nelson to offer AutoCal, but could find no mention of it on his site.  

You know,  I may actually spring for that Range AFM Disable device, and table the tuning for another year.

Nick



 
ltxi said:
This be what we call naive. Look up 4/6/8 Caddy engines from the mid '80's. As with those motors, the 5.3 wasn't designed for AFM.  It's a late life retrofit. Other manufacturers, notably Honda, are using this successfully. GM ain't Honda.

C'mon that not quite fair......used to drive my uncle's Caddy....the GM 4/6/8 V8 was a great idea but way before its time and they were the only manufacturer to even try the concept....... Unfortunately it was implemented using electromechanical solenoids controlling the valve lockup powered by an electronic controller of the VIC 20 era with the brainpower of a digital watch. And on a heavy vehicle like a Caddy or Avy, 4 cylinders is good only while coasting and 8 is needed for power........the idea of going through a 6 mode was stupid altogether because you unbalance the engine with 1 cylinder opposing 2 on the power stroke.....on a positive note it did save a little gas in the 8 mpg era but unfortunately in the 80 cents a gallon era you were better off paying for cheap gas than expensive repairs on a kludged engine. Even so, that engine had guts! And Hondas of that era with all their vacuum controllers for emissions, fluky carbs, rusting fenders and engine supports were only trouble free in their owners' minds.

The AFM system using oil pressure to control valve openings powered by sophisticated electronic controllers worked fine and trouble free on my '07, but nonetheless went to '12 & '13 to get one with the valve cover/crankcase baffle mods as a precaution against the problem in the future. Smooth as silk.....can't feel and don't care when or if it switches from 4 to 8.

 
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