I seem to recall several members here have had problems with early AFM trucks/SUVs requiring new engines at relatively low miles (75k-125k). Has GM fixed this issue? I've seen some inferences on the interwebz that GM made changes around 2010 that supposedly fixed the problem. What says the hive?
No
Have they halfassed their way out of warranty concerns? Yes.
Have they fixed the root of the problem? No.
secretariata wrote: I seem to recall several members here have had problems with early AFM trucks/SUVs requiring new engines at relatively low miles (75k-125k).
They don't need new engines, some dealerships would rather replace a whole engine than pull the heads off and replace the lifters, for whatever reason they have. This may or may not be related to many of the warm bodies in the service department who are proud to not use a torque wrench on anything.
Is the prescribed remedy in a situation like this dealer determined, or per guidelines issued higher up in the OEM's foodchain? Not trying to be argumentative, but instead honestly curious ....
einy wrote: Is the prescribed remedy in a situation like this dealer determined, or per guidelines issued higher up in the OEM's foodchain? Not trying to be argumentative, but instead honestly curious ....
If it's under warranty (Which it usually is) then GM tells us technicians what to do. And unless we can provide overwhelming evidence of severe engine damage, we aren't allowed to just toss a whole engine in there. So usually they get a complete set of lifters, a camshaft if the lobe is rounded off, and occasionally the Variable Lifter Oil Manifold
I haven't seen where it is restricted to certain years, it happened all across the GMT-800 platform, even after the 2010 fix that an earlier poster mentioned but I have never heard off. It's honestly not that common on the GMT-800s though. Our dealership sees maybe one a month tops. The pistons/rings/timing chains issue on the GM 2.4L Ecotec is far worse (We see 3-4 a week) and nobody talks about that one.
The new body style 2014+ trucks have more issues with the AFM. They like to break valvesprings. A lot. Like, as low as 5000 miles. And the bearings also tend to fall out of the rocker arms into the engine. And even when the system works, it causes ungodly driveline vibrations when it goes into V4 that customers complain about and GM buys the truck back. And that's normal.
Does ignoring the recommended oil change interval and going with 4-5,000 mile changes help on the 5.3 lifter issue? I've heard the ecotec problems can be greatly lessened by actually changing the oil more than the recommended once every millennia...
Keep an eye out for the new 2016 cars with AFM. I'd like to note their issues.
There are a few companies out there who are marketing a version of AFM that is quite a bit more. Thankfully, their efforts are reasonably public, so I can mention it. One of their prototypes is a 2011 GMC with AFM in it.
OK, so I have a friend interested in picking up a leftover 2016 full size truck and he has found the best prices on Chevy models. I told him I thought he should look into if the AFM issues had been solved before making a decision. Looking on the internets, I found a GM forum reference or 2 to indicate that some changes had been made to the system in 2010 but there were no specifics on what had been changed. I guess I should have recognized that these may just be BS.
I didn't do exhaustive research, but most of the complaints I found indicated significant oil consumption and damaged components including lifters, cam, and rings. The resolution was either a rebuild or replacement engine. Maybe these were all the worst case scenario vehicles and I just happened to find those posts. They were typically 2007 vintage vehicles so it may be that a lot of the newer vehicles haven't got the same number of miles to suffer similar damage or they are getting caught earlier and fixed before the damage gets that bad.
So it sounds like the issues haven't been resolved, but the problem doesn't happen to every GM vehicle with AFM? Is that a fair assessment? Does disabling the AFM with a tune solve the problem permanently? Just trying to give my buddy some reasonable advice.
alfadriver wrote: Keep an eye out for the new 2016 cars with AFM. I'd like to note their issues.
I have three customers and a friend with '16 Chevy trucks. If they have problems, I'll hear about it!
In reply to secretariata:
No, a tune does not fix the lifters that fail frequently. Oil consumption happens when the lifters fail and leads to the valves staying open and causing the rings to clog up and fail.
And yes I have the same issue with another dod/arm vehicle I have. I have it fixed with a qt of marvel mystery oil currently. I still have not more fixed it with a tune out of the afm.
I do wonder if the increased oil consumption toward the end of an oil change interval in my truck is trying to tell me something about this. It always resets back to no oil used over the first 6k miles when I change the oil soooooo.....no problem?
This thread may have inspired my thread asking about LS builds btw.
In reply to alfadriver:
Not sure I understand your post. Do you mean more GM vehicles with AFM and it is likely to become a more publicized issue due to the greater number of problems? Or that other manufacturer's are coming out with a version of AFM that are better implemented or will provide better fuel economy?
In reply to Ranger50:
So, it's a case of live with it until you have a failure (which may or may not happen), then replace parts to remove AFM, and add a tune to deactivate AFM if out of warranty at that point. Alternately if you make it out of warranty without a problem go preemptive with replacement of hard parts and tune out AFM?
Knurled wrote:alfadriver wrote: Keep an eye out for the new 2016 cars with AFM. I'd like to note their issues.I have three customers and a friend with '16 Chevy trucks. If they have problems, I'll hear about it!
It's also in the Camaro- we've tested one already. Delivers some significant fuel economy improvement, too.
secretariata wrote: In reply to alfadriver: Not sure I understand your post. Do you mean more GM vehicles with AFM and it is likely to become a more publicized issue due to the greater number of problems? Or that other manufacturer's are coming out with a version of AFM that are better implemented or will provide better fuel economy?
For your first, point, yes. The original AFM vehicles were trucks- now they are going into cars. As I mentioned, the Camaro has a model with it.
The second is more 3-5 years out, if adapted. The prototype was on a 2011 GMC Denali. Thankfully- it's publicly out there- http://www.tulatech.com/our-approach.html
And further- as I've mentioned in other threads- engines are most efficient at reasonably high loads- so small engines running hard is more efficient than a large engine not running hard- both making the same power. Which means to meet power requirements- you can make a big engine small (AFM) or a small engine big (boosting). I'm pretty sure we will see more AFM like things happening. Actually, given Honda's VTEC- they would be a massively great candidate to do it- since the mechanism is simple, effective, and reliable.
In reply to secretariata:
I did mine preemptively.
secretariata wrote: OK, so I have a friend interested in picking up a leftover 2016 full size truck and he has found the best prices on Chevy models. I told him I thought he should look into if the AFM issues had been solved before making a decision. Looking on the internets, I found a GM forum reference or 2 to indicate that some changes had been made to the system in 2010 but there were no specifics on what had been changed. I guess I should have recognized that these may just be BS.
Keep in mind that the 2016 uses an entirely different engine architecture from an '07-13 as well. They may have the same displacement but the '14+ L83 EcoTec3 engine is more closely derived from the new Corvette/Camaro LT-1, with AFM and direct-injection and variable valve timing. The big problem these engines seem to have is valvesprings. Seen a number come in with broken valvesprings at random mileages, including a 20K mile Escalade that broke a valvespring, dropped a valve and destroyed the engine.
It's the future.
I trust that GM is taking full credit for the estimated fuel savings in their fleet fuel economy quota for the feds.
crankwalk wrote: It's the future.
Nah, in "the future" the technology is refined enough that it isn't failure prone.
Funny how many of you think the idea of variable displacement is a terrible idea. It's really a good one- you can see and measure the fuel economy benefits. For the rolling AFM, I measured close to 10% FE improvement, especially in the city.
The problem are the problems.... If all of those can be fixed, it would really mean that the large NA engines will come back.
alfadriver wrote: Funny how many of you think the idea of variable displacement is a terrible idea. It's really a good one- you can see and measure the fuel economy benefits. For the rolling AFM, I measured close to 10% FE improvement, especially in the city. The problem are the problems.... If all of those can be fixed, it would really mean that the large NA engines will come back.
I have no problem with variable displacement as a method to improve efficiency. I think what has happened, though, is engines have reached a level of reliability and durability that is very high, and GM's current AFM system is taking it down a notch(or several in some cases). The difference in driveabilty is minor, but it is still noticeable. Makes it feel like a beta test.
eastsidemav wrote:alfadriver wrote: Funny how many of you think the idea of variable displacement is a terrible idea. It's really a good one- you can see and measure the fuel economy benefits. For the rolling AFM, I measured close to 10% FE improvement, especially in the city. The problem are the problems.... If all of those can be fixed, it would really mean that the large NA engines will come back.I have no problem with variable displacement as a method to improve efficiency. I think what has happened, though, is engines have reached a level of reliability and durability that is very high, and GM's current AFM system is taking it down a notch(or several in some cases). The difference in driveabilty is minor, but it is still noticeable. Makes it feel like a beta test.
Very much like my experience with modern CR diesels in small engines with VW a few years ago. Fix after bandaid fix while I'm waiting for a flatbed at 6k miles when the dudes with 1999 ALH TDI's have 300k with just timing belt changes and still get the same mileage. I don't care how much more or less they pollute but breakdowns and catastrophic failures are a step BACKWARDS.
I don't think anybody has a problem with variable displacement engines as long as the consumer forking out the dough isn't the guinea pig. Infiniti's testing of variable displacement looks interesting to me.
In reply to crankwalk:
That's for their variable compression, not variable displacement....
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