IMPORTANT: The Chronicles of Low Oil Pressure by 07burb

[iamdub]

Thank you for the info!

The funny thing is that I spend the most time cruising on perfectly flat roads with relatively little traffic and not much wind for miles at under 60 mph. Basically, North Texas in a nutshell unless I get on the freeway or get stuck in traffic during rush hour. I drive at least 12 flat miles at about 50 mph each day to visit our properties. Some days I drive 100+ miles, probably averaging out at 60 mph (can be boring as hell). Even still, I agree that losing AFM probably won't make a huge mpg impact. Downtime for repairs isn't a killer since our Tahoe is mostly a work vehicle and we have other vehicles.

I did not see a noticeable oil loss over 220 miles of driving. I performed deletes on my 300zx due to concerns about the systems failing prematurely. Now I am wondering if my Z would be worth more in a "stock" condition. Would you pay more for a Tahoe without AFM lifters?

Thanks again

That is funny and you are part of the exception. The flipside to you benefitting from AFM is that means that you USE the AFM more often than others, which means that's more time that those 8 lifters are in their collapsed state. So, you may actually eventually break even with the fuel savings versus extra mechanical upkeep. But, you're still taking a risk and doing damage to your engine. Just to put numbers on the risks (scientific accuracy isn't relative in this point), let's say there's a 40% chance that the AFM won't fail while you own this vehicle. That's still a lot more than the 0% chance it could fail if it were removed.

What sort of MPG do you average with your driving and use of your Tahoe?

Knowing what I know about AFM in these engines, I would absolutely see it's removal as a benefit. Would I pay more because of it? I wouldn't offer more than fair market value just like any other prospective buyer. I would, however, certainly count it as a benefit in my head when considering my bottom dollar in the haggling process.

 

[techbiker]

That is funny and you are part of the exception. The flipside to you benefitting from AFM is that means that you USE the AFM more often than others, which means that's more time that those 8 lifters are in their collapsed state. So, you may actually eventually break even with the fuel savings versus extra mechanical upkeep. But, you're still taking a risk and doing damage to your engine. Just to put numbers on the risks (scientific accuracy isn't relative in this point), let's say there's a 40% chance that the AFM won't fail while you own this vehicle. That's still a lot more than the 0% chance it could fail if it were removed.

What sort of MPG do you average with your driving and use of your Tahoe?

Knowing what I know about AFM in these engines, I would absolutely see it's removal as a benefit. Would I pay more because of it? I wouldn't offer more than fair market value just like any other prospective buyer. I would, however, certainly count it as a benefit in my head when considering my bottom dollar in the haggling process.

I averaged around 22 mpg driving back non-stop from Conroe to DFW. Note that I'm basing this on the fuel gauge since I have only filled up once. I'm currently servicing the vehicle (my thread is in the PPV section).

I suppose my argument is that every system is in a constant state of wear and fails eventually. A system that doesn't exist can't fail. All motors wear out and eventually require rebuilds. I'm really looking for the average time to failure for the AFM system's lifters. Example- Some guys recommend an EGR delete on the 300zx since the EGR tends to fail at high mileage (150k+) and age (15+ years). EGRs do help with emissions testing though (especially since a dyno test is required) and many haven't failed in 25 years.

Another question is- what sort of warning do you get when the AFM lifters start to fail? Will the noise be obvious? If mine start to fail, I will stop the engine immediately and tear it down. These GM part prices have me feeling like a ******* addict in Colombia. I don't mind throwing in new lifters and even a cam if my AFM lifters start to wear out, however a bottom end failure would be tougher.

Great insight.

Thanks again

 

[swathdiver]

...you can start with the base kit that includes just 8 lifters to replace the AFM lifters only or build it up from there with 16 new lifters (my choice) to no cam or a stock cam or one of their performance cams, etc.

You cannot leave your old cam in the motor when deleting the AFM system as the motor will have multiple misfires at idle and throw codes. Gotta buy a new cam as well. Then it is important not to select a camshaft geared for a 3,500 pound car or a 4,500 pound pickup when your SUV weighs over 5,500 pounds.

I have not done the physical delete yet myself nor am I an expert on LS engines or camshafts. However, I have compiled a list of factory and some aftermarket camshafts with their specs and part numbers in excel and would be happy to share it with anyone. It's a work in progress, always being updated.

AFM worked down here in Florida only when coasting down off bridges. While our land is flat, just when the truck levels out and resumes speed the next bridge is upon you and the motor is back in V8 mode. Same thing with city driving, the only time it would kick in was when coasting to a stop. A 6.2 with more HP and Torque may get more use out of it as would a lighter truck with the 5.3. My truck's average daily weight is always over 6,300 pounds.

 

[iamdub]

I averaged around 22 mpg driving back non-stop from Conroe to DFW. Note that I'm basing this on the fuel gauge since I have only filled up once. I'm currently servicing the vehicle (my thread is in the PPV section).

I suppose my argument is that every system is in a constant state of wear and fails eventually. A system that doesn't exist can't fail. All motors wear out and eventually require rebuilds. I'm really looking for the average time to failure for the AFM system's lifters. Example- Some guys recommend an EGR delete on the 300zx since the EGR tends to fail at high mileage (150k+) and age (15+ years). EGRs do help with emissions testing though (especially since a dyno test is required) and many haven't failed in 25 years.

Another question is- what sort of warning do you get when the AFM lifters start to fail? Will the noise be obvious? If mine start to fail, I will stop the engine immediately and tear it down. These GM part prices have me feeling like a ******* addict in Colombia. I don't mind throwing in new lifters and even a cam if my AFM lifters start to wear out, however a bottom end failure would be tougher.

Great insight.

Thanks again

Cruising at 70-75 through the Florida panhandle, Alabama, Mississippi and eastern Louisiana, I averaged 21 and was almost at 22. AFM was constantly on and off because there are slight inclines and declines the whole way. Based on this and assuming that your drive is flatter, I'm quite sure that you may lose 2 MPG at the most, but I'm betting on you losing slightly less than that. It's all pennies when considering what you'd be spending to keep AFM, not to mention a failure from it.

There's no set mileage as to when the system commonly fails. I've read stories on here of failures happening well under 100K miles and a well over 200K miles. If I had to narrow down a number, I'd say it's a "150K-mile design". Yes, all engines and systems wear out. But I've heard of and personally seen too many 300k+ miles (and a few 400k-mile) Gen3 engines to count. The volume of these "champion engine" stories have quickly dwindled since the advent of AFM.

To be fair, you have to consider the other factors such as how the engine was maintained. That's a variable we'll never be able to tie to the general mortality rate of AFM engines.

There's usually not much warning for when the AFM system fails. It seems most stories start with "I was driving when suddenly all my warning lights on the dash lit up and the motor started running rough...". I'd say that if there's any forewarning of any kind, it's lifter ticking at startup then maybe lifter ticking while driving.

 

[iamdub]

You cannot leave your old cam in the motor when deleting the AFM system as the motor will have multiple misfires at idle and throw codes. Gotta buy a new cam as well.

I've heard both ways. Texas Speed swears you can keep the AFM cam while many others say you can't. I'd rather not keep it. A local performnce shop here says they like to use the stock cam from the Gen3 5.3 when they do an AFM delete and the customer doesn't want a performance cam.

Then it is important not to select a camshaft geared for a 3,500 pound car or a 4,500 pound pickup when your SUV weighs over 5,500 pounds.

Absolutely. Horsepower sells cars, torque moves them.

I have not done the physical delete yet myself nor am I an expert on LS engines or camshafts. However, I have compiled a list of factory and some aftermarket camshafts with their specs and part numbers in excel and would be happy to share it with anyone. It's a work in progress, always being updated.

So I've seen in your previous posts. This info is invaluable and your sharing it is much appreciated. It's a huge step towards choosing a cam because all you gotta do is Google the main specs and you're bound to find forums where this cam is discussed and/or YouTube videos of it.

AFM worked down here in Florida only when coasting down off bridges. While our land is flat, just when the truck levels out and resumes speed the next bridge is upon you and the motor is back in V8 mode. Same thing with city driving, the only time it would kick in was when coasting to a stop. A 6.2 with more HP and Torque may get more use out of it as would a lighter truck with the 5.3. My truck's average daily weight is always over 6,300 pounds.

Agreed. The system may perform better and return better MPG. But, that would mean it's engaged that much more which may mean it's more likely to fail and/or fail sooner. It's very much a double-edged sword, IMO.

 

[swathdiver]

Justin at Black Bear told me that his tunes are usually worth about a 2 mpg increase in economy. So even turning off the AFM, the engines run more efficient and get better mileage. Even mine own experience seems to "bear" this out!

TSP I believe has since come around on that. There is misinformation regarding which stock Gen III cam to use as well. "They" say to use the LM7 camshaft but it is much smaller than our stock cams, our profiles match the L33s cam specs.

When I say "our profiles" I'm referring to the 2007-2009 LC9, LMG and LY5 5.3 engines. All of these motors shared the same camshaft. The LC9 and LMG received VVT in 2010 along with a new camshaft grind and the non Flex Fuel LY5 was dropped.

 

[07 black beauty]

I am curious, when you put vehicle into tow haul mode does it disable AFM ?

 

[PG01]

I am curious, when you put vehicle into tow haul mode does it disable AFM ?

No. But if you leave it in 5th gear if 6sp, 3 in a 4sp or 7 in an 8sp it will not come on. Is it possible to do that all the time or should you, no. Around town town maybe but at highway speeds you really aren’t letting truck go into OD

 

[swathdiver]

I suppose my argument is that every system is in a constant state of wear and fails eventually. A system that doesn't exist can't fail. All motors wear out and eventually require rebuilds.

This refers to the Law of Entropy. Evolutionists love to ignore this one!

 

[savagebasher]

My 07 with 118k had the low oil pressure issue today.. it is at the shop now. No CEL but the oil light was on of course and DIC warning.. the gauge would drop to 0 and then spike up with I got on the throttle. I drove it 20 min to the shop and it seemed fine otherwise.. hoping it is just the 0 ring, sensor or blocked screen. Will let you guys know. :/ I just used Amsoil Signature and Filter (Wix IIRC) 5k miles ago so maybe that just loosened up some sludge.