Active Fuel Management

[goblue]

Originally Posted by vitonvalve

Great info. How can you turn it off?

Why? Sounds like a knee jerk reaction to some innovative technology

[scooter10572]

why would you turn off something designed to save 4 dollar a gallon fuel?????? anyway you cant from gm anyhow

[Wurtle38]

I've got a '78 Lincoln Continental I working on and thinking I want a little more fuel efficient engine then the 7.5L V8 it came with. I've been reading the new camaro is supposed to have an AFM L99 putting out 400hp and a 6 spd auto. does anyone know if you can buy the drive train on the aftermarket and how much it would cost? or what kind of power does the 5.3L put out and how much would it cost? it's hard to find a price on engines in general. the lincoln is getting a body off and I know any block will fit in that huge engine bay so I'm not worried if it won't bolt right up, I'll make it fit. by the way I'm a chevy guy so I'd rather have a chevy engine in it.

[1999 White C5 Coupe]

I purchased a new 2008 Impala LTZ with the 3.9 V-6 and AFM. I see for 2009, the feature has been dropped from the 3.9 V6 Impala engine.

Anyone know why GM has dropped this feature?

[ggcurtis]

Yea what a knee jerk, I traded for a new 08 and to my suprise all 5.3 silverados have AFM. I still say its junk the new one also jerks, I guess my reaction time is too quick, according to GM it flawlessly changes in 250mili seconds and I can tell you everytime and what mode its in. Also both of my 5.3 with AFM suffer lower gas mileage than the 2006 model 5.3 or the 2003 models that I owned. You guys can say what you want the 2007 Silverado crew cab Z71 2wd listed 22 MPG on the sticker for HWY MPG, who are you kidding. I have always been loyal to GM but something is going to have to give this is getting crazy. I got better mileage with my 5.7 vortec, what the hell is going on.

[Dr. Show-Me]

Can the Chevy smallblock run on 2 cylinders using an AFM approach? If so, highway mileage, according to the EPA, could be high 30s.

[ZZ71]

I got a 2008 GMC Sierra SLT E. Cab Z71 with 11,000 miles and have an ongoing problem with AFM for the last few months. My truck vibrates/shudders when its in V4 mode. Dealer people and I both drove an identical truck and it did not do what mine is doing.

They found NO codes set or anything wrong. A search found a TSB relating to a check ball in the trans that sticks and will cause a harsh TCC lockup and vibration when in A4 mode is so equipped (2005-2008 trans).

Whenever the V4 mode engages at lower speeds (whenever you let of gas at less than 40mph) and you have to maintain constant speed, the engine vibrates (or shudders as I call it) it does not switch to V8 mode right away, you have to give it more gas to make it switch and then you risk the chance of rear ending someone in close traffic. Kind of like with a carb where the accelerator pump was faulty and you stepped on the gas and nothing happened but then suddenly it went.

The SM is calling in to GM tech line today tp see if they can find a solution.

Dealer will not disable AFM but Wester's will for $595.

Btw - All the talk about AFM being good for mpg, I am only getting in the mid 16's with this, best on the highway is 18.1. I never speed or hotrod, rarely drive over 65mph. My 2004 got this mpg so all those who claim over 20, I don't see it with my truck. My truck was built in June of 2007.

[richbois]

My girlfriend has a 2007 Tahoe LTZ and when she first got it it was getting great milage 16 to 18 mpg around town and up to 26 on the open road then all of a sudden it droped almost 6 to 9 mpg getting only 9 to 10 mpg around town to 17 on the open road. We have noticed the V4 to V8 mode has staying in the V8 mode most of the tme it takes a lot to make it go in V4 mode. We have taken it in and the dealer and GM it's self both have said it is normal and there is no reason give for the extreme drop in milage. Also noticed several other problems with the vehicle sometimes when you use the remote start when you go to unlock the doors it stop the mortor it has happened at least 15 times and nav system is not very accurate some times as much as two blocks off. Also we haven't received the promissed update for the maps the owners manual said we should receive a postcard on the first year date and that was like two months ago and still nothing. At this time we are not very happy with GM and wish we haven't gotten the truck not received very good results an our many trips to the dealer even had a second dealer look it over and the same results.

[oklapike]

Originally Posted by Triple-X08

havent seen any issues yet with the 5.3 AFM system, seen a few 3.9 v6's with the system and it has a voltage regulator problem.

the only issue you will have with that car is the tire pressure monitor. new impalas and monte carlos have problems with them.


the 5.3 is a good engine, and it has alot of torque. i have owned a few monte carlos, i love them.

Same here, 26K miles on my '08 and no AFM issues. I haven't even seen any issues with my tire pressure monitor.

[wooderson]

I know that the system kicks in automatically, but is there any indication to when it is actually functioning something like an indicator on the dash?

[AirCleaner]

The system has come along way from the old V-8-6-4 days thats for sure !

[ARMYDUDE]

My first truck was a 73 Chevy and I have owned at least 1 body style of every model since. My latest is the 08 Z71 with AFM...I HATE IT! I agree with other posters about mileage. My 06 Z71 averaged 19 on the HWY. I just returned from an 800 mile trip and barely averaged 17! I'm a truck guy and the FIRST thing that goes on are dual exhaust... this AFM 4 cyl tone drives me crazy.

Now, I'm not a techy....but what makes the AFM work? What tells the engine to shift from 8 to 4? A computer program right? GM techs are lying dogs if they say they CAN'T turn it off...it ain't nothing but a program that needs to be RE-programmed! It's not that they CAN'T...It's that they WON'T!

Something better change pretty quick or I'm buying a Hemi. GM should have kept the best engine of ALL time anyway...the 350!

[1999 White C5 Coupe]

Originally Posted by wooderson

I know that the system kicks in automatically, but is there any indication to when it is actually functioning something like an indicator on the dash?

On my 2008 Impala LTZ with AFM - you can scroll through a menu on the driver information center and find a screen that displays "6 cyl" or "3 cyl" - telling you which mode that it is in.

I would have like a small display that you don't have to scroll through to determine if the AFM is operating.

For 2009 - the AFM was discontinued on the 3.9 litre 6-cylinder Impala. I do not know why. I do know that my 2008 Impala with the 3.9 litre AFM engine does NOT get the fuel mileage that is advertised, using regular unleaded gasoline (87 octane).

[Dr. Show-Me]

Couldn't this be simplified by using direct gas injection, and shutting off the fuel to the cylinder?

[red_rider]

Originally Posted by ARMYDUDE

My first truck was a 73 Chevy and I have owned at least 1 body style of every model since. My latest is the 08 Z71 with AFM...I HATE IT! I agree with other posters about mileage. My 06 Z71 averaged 19 on the HWY. I just returned from an 800 mile trip and barely averaged 17! I'm a truck guy and the FIRST thing that goes on are dual exhaust... this AFM 4 cyl tone drives me crazy.

Now, I'm not a techy....but what makes the AFM work? What tells the engine to shift from 8 to 4? A computer program right? GM techs are lying dogs if they say they CAN'T turn it off...it ain't nothing but a program that needs to be RE-programmed! It's not that they CAN'T...It's that they WON'T!

Something better change pretty quick or I'm buying a Hemi. GM should have kept the best engine of ALL time anyway...the 350!

From what I've heard, it's relatively easy to turn off yourself, you should look into doing it.