have a great day!
have a great day!
I'm not doubting that you had problems with your AFM, just that EVERY AFM engine is flawed.
Truckman, are you aware of the AFM oil consumption TSB?
It is a documented issue and the TSB fix (oil mist deflector) only helped marginally.
GM also acknowledged lifter issues back in 2007/08 and they were replacing them if they were noisy for more than 45s-60s upon cold starts. My dealer confirmed this as I left my truck overnight on a cold night so they could diagnose it. Mine was borderline and I chose to not have them replaced because they were not installing newly designed lifters, but the same lifters and it was a crapshoot whether or not the problem would go away.
Bottom line is these were NOT isolated issues, they were widespread.
based on what I am reading about this new issue it's still lifter related and the software fix causes AFM to not activate as much/as long to prevent lifters from losing pressure. Do you really call that a fix? Sounds kinda like the "fix" for the washer fluid heater issue. LOL
Curiously enough from what I can tell the new and older motors use the same lifter. I don't have a way to confirm if GM has updated the part number along the way and the latest number is a replacement for what was originally put in the old motors.
That said I have read the actual GM campaign regarding this issue and from the way I interpreted it under certain instances the software may attempt to open the valve against cylinder pressure. IMHO this would be really hard on all of the valvetrain with the lifter probably taking the worst beating. It didn't sound like it happened all the time just under certain conditions. My guess is you beat on the lifter enough and it fails. It sounds like they identified the issue and corrected the software to not open the valve against cylinder pressure and that should be the end of the issue.
What I find interesting is the update is only for the 5.3 where the 4.3 and 6.2 also use the same lifter. Probably some random line of code in the 5.3 program that did something it wasn't supposed to do.
If you have ANY reliable evidence to the contrary, please post it. Otherwise, you're spreading rumors and misinformation just like the OP of this thread.
The reason that this likely only pertains to the 5.3L is that only very early engines are affected. The newer engines liely already have the correct software. The 5.3L has been out for months before before the other two.
And right, if you read the TSB, it mentions activation under high pressure as being the concern. Could be as simple as delaying the AFM activation on a down stroke or different stroke. I put no value in comments related to AFM not activating as much. As we can see by some of the posters in this thread, people's perception and reality can often be widely different.
You know a debate is getting good when the "I've bought GM products all my life" argument comes into play.
Do a Google search on "GM AFM Issues".
And a forum/thread where people specifically go to post complaints is not statistically relavant at all.
I have a somewhat unique perspective having 25+ years of experience as an automotive technician and working in an area that is comprised mainly of GM cars. I own a fairly well equipped independent repair shop. 78% of my business is on GM vehicles and the dealer I ordered my truck through advertises GMS employee pricing on their website and indicates that 70% of their business is GM employees. With several GM plants in the area I am guessing we have a bit more GM vehicles running around here than most places.
That said we see very few trucks for any issues at all. We have seen a few AFM equipped trucks for oil consumption issues but not any more than other vehicles. The only single lifter issue on an AFM vehicle I have ever witnessed was on my counterpart at what used to be our second location (He and myself bought the individual shops from the previous owner last year) His Suburban would intermittently rattle on startup for a minute or two. He had the local dealer do the lifters under warranty and end of issue.
I myself will chalk the large number of online complaints up to those people who do have issues seeking out information via the web and congregating on the various forums. My guess is there is a much larger amount of owners out there who do not have any issues.
I am not saying it is a non issue just that out of all of the large amount of AFM vehicles GM has built over the years the percentage of them with problems is probably smaller than you would think. At least that has been my experience working in the industry.
I explained in my forum example that the sampling was from existing members that were on GM-Trucks. Not new members that joined after experiencing the issue. A poll was done among long-time members and the majority of the regular posters that had purchased GMT900's did have oil consumption and/or lifter noise. I realize this is a small sampling, but if it were only 10%, then that should have been reflected in that poll, at least closer than 75-80%.
The oil consumption issue is inherent to the design of the system, it is not due to a faulty component. This alone tells me that it is going to be in most, if not all, engines...at least to some degree.
I guess what I would say is the incidence of issues on these vehicles are no higher than other vehicles we see. Quite the contrary as I said the trucks seem to have less issues than the cars.
If you have ever looked at the vehicle manufacturers (any of them) TSB listing it would scare you. There are literally hundreds of TSBs for everything you can imagine, not every vehicle will have all the issues but it puts it in perspective about how many things can go wrong when you build thousands of vehicles.
Funny how my SA and SM both told me the AFM oil consumption was a HUGE issue and they could barely keep up with the TSB fix and also the lifter noise issue (though that was less frequent...most likely due to most people not noticing it).
Design flaws such as the root cause of the AFM oil consumption, as opposed to part defects, are typically widespread. Piston slap is another example of a widespread issue based on design, not a defect.
Wow, this thread has certainly gone sideways. Whether it's a recall or tsb is immaterial. My reason for posting it was because I found it on another forum and had not seen it here.
My last GM (01) did not have AFM, so its operation in my 14 is new to me. It is similar yet very different from how Honda does it. We've had two Hondas with AFM (thankfully no problems), and they activate very predictably. By comparison, the V4 mode in our Sierra seems to have a much more complex algorithm which makes it almost impossible to predict when it will activate. There are times going downhill that it stays in V8, there are times uphill it stays in V4, and everything in between.
One marked difference to Honda is they do not allow partial cylinder operation until the engine has warmed up, whereas GM allows it almost instantly after a cold start. In execution both Honda and GM go in and out of partial cylinder operation almost undetectably, but with a noticeable change in instantaneous fuel economy.
Another difference, this time between the Sierra and the 07 Tundra I traded in, is that the Sierra idles at a much lower rpm, which itself no doubt saves some gas since an idling engine gets zero mpg. And for the record, after 85K miles my overall average with the Tundra 5.7 4x4 was 15. After 10K miles my overall average with the Sierra 5.3 4x4 is 20. How much of that 33% gain in mileage is from AFM? I don't know, but can tell you the instantaneous mileage readout generally makes a healthy jump from V8 to V4, e.g., from about 24 to about 35, so a 50% increase. If anyone knows how to get it to stay in V4 mode more often, I'd welcome it.
So if you have a 14, take an hour at the dealer and get the updates. I didn't notice any difference before and after, and this way if the engine does break no one can blame me for not getting GM's recommended software updates completed in a timely manner.
"October 23, 2013 - Honda has agreed to settle a massive class-action lawsuit brought against it for engine trouble potentially affecting nearly 1.6 million vehicles. The lawsuit includes Accord (2008-12), Odyssey (2008-13), Pilot (2009-13) and Crosstour (2010-13) models equipped with the 3.5-liter V6 with Variable Cylinder Management, which might experience engine misfire, excessive oil burning and premature spark plug fouling issues."
Do a google search for AFM recalls and this thread and the one at GM-Trucks are the top two in the list for a non-issue.