New GM Motors (Variable Valve Timing)

[MadOgre]

Anybody know anything about the new GM 1/2 ton VVT AFM engines? Are they reliable? Are they expensive or inexpensive to maintain or are they a nightmare waiting to happen?

I cant seem to find any real info on these engines. Does anyone know where a guy could find out about these engines? And the transmissions used behind them?

I remember when the Cadillac's used this technology and were touted as the most advanced and reliable technology lol. Well we all know how that went! So it would be nice to avoid these engines if its just gonna be another case of Deja Vu !!!

I find it interesting that only the 1/2 tons use the VVT engines in 4.3, 5.3, 6.2 where as the 3/4 and 1 tons all use a 6.0 with out the VVT AFM

 

[MadOgre]

@Keith Seymore

 

[mistaake]

Variable Valve Timing is not inherently unreliable. I would be more worried about DOD/AFM (Deactivation on Demand/Active Fuel Management) where it disables combustion in half the cylinders under light load conditions.

Ever since this was introduced to the 5.3L V8 engines in the half ton full-size trucks and SUVs there have been many reports on forums with people blaming this system for everything from oil consumption to ticking noises to complete engine failure both within warranty and after. There are plenty of high mileage trucks/SUVs with AFM with no problems.

While there is definitely a possibility that something this complex can fail and personally if I purchased a used truck/SUV with AFM I would consider disabling it with something like the Range AFM disable device that plugs into the OBD2 port, I don't think it's as big of a disaster as you would think by reading forums. Only people that have problems with it post on the forums, while people that think it's great and have never had an issue are not likely to speak up - why bother discussing something that just works?

It's been many years since 2007 so I'd venture to say that a new vehicle with AFM would not be less reliable than a new vehicle without AFM since they have had time to work out any bugs, if they even had any. Personally if I purchased a new vehicle with AFM I'd probably leave it alone.

I will say, though - the drama surrounding AFM made me pick the 07 Colorado with 70K rather than the 09 Silverado with 160K for just $1k more. In hindsight I made the wrong choice and should have got the Silverado - this Colorado is a piece of junk. Well, actually I should have held on to my 1983 C20 but that's beside the point.

 

[Pender1]

I had a 2011 Silverado and I now have a 2014. I've never had any serious issues out of either of them, but I will say the AFM in the new motor is greatly improved. I believe GM learned from their mistakes on that system. I sold my '11 with 50k miles on it and have <30k on my '14, so relatively low mileage. My brother has a '11 GMC with ~80-90k miles on it and the only engine related issue he's had is a spark plug cracking and causing misfires. My dad had a '07 GMC and it was a piece of crap. Burned oil from the day it was new, constantly being worked on for this or that little problem. Never any gigantic problem, just continuous little problems.

I say all that to say this, my family has put a lot of miles on GM trucks in my life (we've collectively owned 17 GM trucks and SUV's that I was old enough to remember) and I can say in my personal opinion that the new ('14+) motors are an improvement in almost every way over previous generations.

Just for my own sake I'm going to list the ones we had to see if I can remember them all:
-'73 GMC C1500
-'89 GMC C1500
-'92? GMC C1500
-'95 GMC C1500
-02 Yukon 2wd
-0? Tahoe 2wd
-'04 Yukon 2wd
-'00 Blazer 2wd
-'97 Chevy C1500 <-mine
-'84 Chevy K10 <-mine
-'11 GMC 4wd
-'11 Chevy 2wd <-mine
-'05 GMC 4wd
-'14 Buick Enclave Awd
-'9? Astro van
-'07 GMC 4wd
-'14 Chevy 4wd <-mine

 

[Old77]

I can say in my personal opinion that the new ('14+) motors are an improvement in almost every way over previous generations.

^^^exactly this....last year my father purchased a new 14+ crew cab. Every since then I've been peppering him with questions regarding his truck focusing in on how the drivetrain performs and it's been nothing but positive feedback and he's had no issues thus far and has driven it over 20k miles already. I've driven it a handful of times and compared to the previous generations the 14+ is leaps and bounds better in every aspect whether in drivetrain performance, interior, creature comforts,......whatever. And MPG is vastly improved. He gets 23 mpg on the highway and around 18-19 in city.

I've had numerous GM fullsize trucks/suvs between 2000-13 and the newest generation just leaves all of them in the dust.

 

[Pender1]

interior, creature comforts,......whatever.

I just hate the stupid touch screen radio. It's not very responsive.

You're right about the MPG though, I went from a 2wd old engine to a 4wd new engine and gained ~3mpg. And good lord is this thing quiet.

 

[Old77]

^^^exactly the same for my dad. He went from a '12 2wd crew cab to this '14 which is a 4wd crew cab and gained MPG pretty substantially and you're right, the thing is really quiet on the inside. The touch screen does take some getting used to but the times I've driven it I didn't have too many problems with the one in his. It also had pretty decent acceleration which surprised me being completely stock.

 

[MadOgre]

Well I found this article plus a few others about the VVT and it looks like a real good and simple performance upgrade to any LS engine! Should be quite reliable too

http://www.hotrod.com/how-to/engine/hrdp-1007-gms-variable-valve-timing-system-performance-test/

The AFM on the 1/2 tons seems to be better since 2014 but still nothing that I want to spend 40K + on !!!

Apparently you can get a ranger unit to disable the AFM but it has to stay physically plugged into the OBDII port to work and doesn't actually alter the ECM programming in any way which could be good for warranty issues. Simply remove it and take your vehicle to dealership for warranty repair work!

The down side to disabling the AFM is that there was a recall for AFM trucks because they were idling in V8 mode instead of V4 mode and this was causing excessive heat from the exhaust and actually starting fires. The conspiracist side of me says that it may just be a rouse to keep people from deleting the AFM on there vehicles as the delete would = lost revenue from engine repairs and sold parts as well as the need to purchase a new vehicle after your AFM engine kicks the bucket due to running in AFM mode. The reason being that only 4-8 vehicles have ever had this "heat" issue but despite this a fleet wide 2014 recall was ordered !!! Sounds funny to me but may be completely true. I dunno.


At any rate the AFM seems to be a bad technology as far as reliability and engine longevity is concerned. Although there doesn't seem to be much info available for the new and improved 2014-15 application of the technology.

 

[Old77]

Time will tell on the 14/15 and reliability effects. At least this newest iteration actually yields good fuel economy as opposed to the previous iterations which were useless nonsense

 

[MadOgre]

Apparently the 07-13 setup shut down the same 4 cylinders every time. The new version will cancel any of the 8 and not necessarily at the same time either. It is supposed to be a fully ECM controlled system that uses a large amount of variables to determine which and how many cylinders shut down. And instead of shutting down 1 cylinder for say 4RPM it will shut down 2 for 2RPM or 4 for 4RPM, type thing. This is supposed to work better for performance and tries to eliminate specific cylinders from going bad because they are always being shut down. Its supposed to even out the system.

I dunno it still sounds like a gimmick to me especially when you can get better fuel saving results simply by doing a better job with gearing ratios.

And only the lower priced 1/2 tons utilize this technology! Thank God I only have to pay another $15K to get a real truck LOL

This does not sit well with me and my GM loyalty.

They should have at least one engine option in the 1/2 ton series that does not use this useless technology! BUT I guess if they did that it would only expose the fact that the AFM is utterly useless technology!!! Proven by the fact that it is not incorporated into the heavier series truck that people depend on to make a living and is most often sold as fleet trucks. The same people that would really like to have a fuel saving vehicle So obviously it is not reliable and doesn't really save any fuel consumption at the end of the day.......otherwise it would be incorporated across the board !!!

Well at least I can have my WiFi so I can google the nearest dealership to have my useless $45K 1/2 ton truck towed to. What a joke!!!

 

[MadOgre]

I was looking for either a 4.3 V6 or 5.3 V8 $35K-40K to use as a family vehicle with short commute trips. But NOOOOO I now have to buy a $55K 3/4 ton truck with a 6.0 just so I can have a reliable vehicle that is worth spending money on!

$40K on a piece of **** or $55K on a way over built truck then what I need but at least it should be problem free I HOPE !!!