2014 chevy Silverado active fuel management

ZmanII · January 25, 2014

I hope GM fixed AFM. My 2011 5.3 AFM Avalanche has been a nightmare with AFM. I had the motor rebuilt at 30k miles due to oil consumption. GMs handling of oil consumption is horiible. I had 4 check engine lights due to misfires on cylinders 1&7 before they attempted to resolve the problem, instead of attempting to patch it. On the highway, I would consume a quart of oil every 5-600 miles. I had to add a quart everytime I stopped for gas!!

My hope is that with AFM in the vettes now, GM spent a lot of time studying what went wrong. The previous gen AFM was added to an existing engine which probably led to a lot of compromises being made. My buddy has a Ram with the hemi and their version of AFM without any problems or oil consumption.

I don't understand the complaints about lag going from v4 to v8 mode. It happens in one revolution of the engine. If you stomp on the gas, it changes to v8 instantly.

TxTruckMan · January 25, 2014

I hope GM fixed AFM. My 2011 5.3 AFM Avalanche has been a nightmare with AFM. I had the motor rebuilt at 30k miles due to oil consumption. GMs handling of oil consumption is horiible. I had 4 check engine lights due to misfires on cylinders 1&7 before they attempted to resolve the problem, instead of attempting to patch it. On the highway, I would consume a quart of oil every 5-600 miles. I had to add a quart everytime I stopped for gas!!

My hope is that with AFM in the vettes now, GM spent a lot of time studying what went wrong. The previous gen AFM was added to an existing engine which probably led to a lot of compromises being made. My buddy has a Ram with the hemi and their version of AFM without any problems or oil consumption.

I don't understand the complaints about lag going from v4 to v8 mode. It happens in one revolution of the engine. If you stomp on the gas, it changes to v8 instantly.

I asked 2 different dealers about oil consumption and previous AFM. They both gave the same answer - there were some people with issues (especially in the beginning), but the numbers weren't are large as people seem to think. But GM has said that they've continued to make improvements with AFM.

And I'm with you on AFM switching from V4 to V8 - it's instantaneous and unperceivable. I think that most people are feeling the transmission switch gears, not AFM switching. The transmission is not nearly as smooth as I would like. I'm just thankful that GM didn't have the 8 speeds out yet.

pm26 · January 25, 2014

I asked 2 different dealers about oil consumption and previous AFM. They both gave the same answer - there were some people with issues (especially in the beginning), but the numbers weren't are large as people seem to think. But GM has said that they've continued to make improvements with AFM.

And I'm with you on AFM switching from V4 to V8 - it's instantaneous and unperceivable. I think that most people are feeling the transmission switch gears, not AFM switching. The transmission is not nearly as smooth as I would like. I'm just thankful that GM didn't have the 8 speeds out yet.

The 8 speed automatic is coming. It is only a matter of time. The ridiculous EPA mileage goals will force the manufacturers to go to ridiculous number of gears. Why don't they just come up with an 11 speed automatic and be done with it for at least a decade.

MikeNH · January 25, 2014

As long as the trucks continue to come with the range select/gear lockout I could care less how many gears is has so long as I can lock it into going no higher than direct drive (1:1) in town or into lower overdrives if towing or in hilly terrain.

Daryl Z71 · January 25, 2014

I just think it's a waste as AFM is not a problem. That's why I call it snake oil. YOu're paying more to waste more gas.

Tell us it's not a problem after 200k miles. Big deal about using gas, it's a truck. If your worried about gas you should have bought a car. Garbage fuel saving gimmicks like AFM shouldn't even be on a truck.

ZmanII · January 26, 2014

The 8 speed automatic is coming. It is only a matter of time. The ridiculous EPA mileage goals will force the manufacturers to go to ridiculous number of gears. Why don't they just come up with an 11 speed automatic and be done with it for at least a decade.

I think the eight speeds will be better than the 6 speeds, as long as they put in a true overdrive. When they went from the 4 speeds to the 6 speeds, the ratio for 6th was similar to 4th in the four speeds. I gained less then 1 mpg on the highway going from 4spd non AFM to 6spd with AFM. On paper, it was supposed to be 3mpg better on the highway. The acceleration of the 6spd versus 4spd was a huge difference, but no real gain on mpg.

pm26 · January 26, 2014

Tell us it's not a problem after 200k miles. Big deal about using gas, it's a truck. If your worried about gas you should have bought a car. Garbage fuel saving gimmicks like AFM shouldn't even be on a truck.

Finally someone says it like it is. Agree.

tbarn · January 26, 2014

Just to add a little perspective here, the 2013 4 speed 4th gear ratio is .696:1. The 2014 6 speed 6th gear is .667:1. and the dodge ram 8 speed 8th gear is .670:1. All about the same.

Ron.s · January 26, 2014

Just to add a little perspective here, the 2013 4 speed 4th gear ratio is .696:1. The 2014 6 speed 6th gear is .667:1. and the dodge ram 8 speed 8th gear is .670:1. All about the same.

Rear end ratio and tire size also affect engine RPM's at any given speed. My 6.2 with 3.42 gears runs about 2,000 R's at 80 MPH. It's really that final ratio that provides the most accurate measurement of gearing comparing one vehicle to another.

Ron.s · January 26, 2014

Comparing AFM results mentioned above to my actual there seems to be a wide disparity in how often AFM runs in V-4 mode. Mine is rarely in V-4-I have to coax it by letting up on the gas and then the slightest Increase in pressure on the gas pedal and it's back in V-8 mode. Works better coasting downhill but requires some throttle pressure even then! If I start down a steep grade and let off the pedal completely then it stays in V-8 mode. I agree with the "Why on a truck" theory. If it was really "light throttle pressure" then I could rationalize the benefit for city driving. Mine does change instantly and does so smoothly but ??? Maybe they backed off the AFM management on the 6.2's for some reason.

MikeNH · January 26, 2014

The fuel injectors turn off when coasting under most circumstances. No benefit to AFM being on when coasting.

OUSux · January 26, 2014

Hey Fondu, let us know how it impacts the MPG when you have a chance. I was looking at the same module and noticed theres one for better MPG but it just makes no sense turning our trucks into 4 bangers
Sorry to say this, but the way things are going with the government unrealistic mileage requirements,

it looks like someone will be driving 4 cylinder turbo engine trucks in very near future. With even higher sticker prices.

Or smaller displacement Turbo diesels

TxTruckMan · January 26, 2014

Tell us it's not a problem after 200k miles. Big deal about using gas, it's a truck. If your worried about gas you should have bought a car. Garbage fuel saving gimmicks like AFM shouldn't even be on a truck.

I'm not worried about gas mileage myself, but some people do. I'm also not worried about unfounded AFM problems. Where are all the GMT 900 trucks with high mileage AFM problems? There aren't any. You're being paranoid.

I think the eight speeds will be better than the 6 speeds, as long as they put in a true overdrive. When they went from the 4 speeds to the 6 speeds, the ratio for 6th was similar to 4th in the four speeds. I gained less then 1 mpg on the highway going from 4spd non AFM to 6spd with AFM. On paper, it was supposed to be 3mpg better on the highway. The acceleration of the 6spd versus 4spd was a huge difference, but no real gain on mpg.

The big issue with highway mileage is not the OD ratio of the tranny, it's the aerodynamics of the truck and people's speed. There's little that can be done to improve mileage above 70 mph unless you want your truck to look lime a prius. More gears alone won't do much for highway mileage, maybe 2-3%.

Stex · January 26, 2014

I asked 2 different dealers about oil consumption and previous AFM. They both gave the same answer - there were some people with issues (especially in the beginning), but the numbers weren't are large as people seem to think. But GM has said that they've continued to make improvements with AFM.

Of course they said no!!! I have seem the 5.3s torn down in my dealers shop for oil consumption problems related to AFM. Mine started at about 50,000 and my salesman at the dealer says his is just below 2 qts burned in 5.000.

Better hope they fixed it because it was wide spread in the 900s. Usually comes on with miles as rings get clogged. The fixes by GM were, valve cover change, baffle mod in pan, mod PVC set up and new rings and pistons if needed all along with new lifters on the early 900s.

Trust me, if your '14 starts burning 2qts on a 5,000 mile oil change and GM says within tolerance you will be very unhappy. Even if they do fix it, who wants their engine gone thru by maybe a good/bad tech.

I would put a catch can on these '14 as the problem seemed to be too much return of oil to the engine thru the PVC. And add the range. I am not buying a damn thing tell the '14s get some miles on them and I see no oil issues.

Here is the oil burn pinned thread in the 900 section....last ten pages tell where it is going now...

http://www.gm-trucks.com/forums/topic/127812-is-your-gmt-900-truck-or-suv-using-oil/