Active Fuel Management - Page 5

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Thread: Active Fuel Management

  1. #61
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    Re: Active Fuel Management

    Quote Originally Posted by ogg vorbis View Post
    AFM does, in fact, cause increased oil consumption.

    When the valves shut, and the piston travels downwards, it creates a vacuum, which sucks in oil.
    According to the AFM description in post #49 above, the intake valve is open 'til the lifter is on the cam lobe base circle which would minimize any vacuum being created since the piston would be near BDC.
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  3. #62
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    Re: Active Fuel Management

    Quote Originally Posted by Jim Injun Ear View Post
    The high oil consumption has little to do with AFM, it is driven by extended oil changes, degraded oil, ring land deposits, and the associated stuck piston rings all of this allows increased crankcase pressure/vapors. Which in turn, these oil vapors are pulled through the PCV system through the throttle body. Causing throttle body deposits, intake port deposits, intake valve deposits, combustion chamber deposits, and degradation of the catalytic convertor. Cats do not like oil related deposits, and these deposits negatively effect convertor efficiency.

    There is also a valve cover issue that increases PCV pull over, but that condition is massive oil consumption.
    AFAIK, the 6.2 that didn't have AFM, didn't suffer from high oil consumption w/ the same extended oil changes.
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  4. #63
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    I'm about to purchase a 2004 Silverado 1500 5.3 v8 with 45k miles. I was just notified by a mechanic about the afm issues in some of the older models. I was hoping someone could confirm that this 2004 v8 is not an Afm engine, or an engine that suffers from increased oil consumption? As the earliest is the 2005 envoy that had the afm? Hoping someone could confirm or provide any assistance, thanks.

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  6. #64
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    Re: Active Fuel Management

    There was a good 4 page article about cylinder deactivation in the Sept 2015 Automotive Engineering magazine. The article was called: Leading the attack on engine pumping losses. The article explains the difference between the gen 4 and gen 5 engines and how GM is far ahead of the others with experience. Right now, GM, Honda, FCA, and VW is using cylinder deactivation and Ford is close to using it.

  7. #65
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    Re: Active Fuel Management

    Hello, I just bought a 2008 Impala 3.9, on 4/20/16, 100,151 AFM equipped with lifter/tappet noise, engine shakes at idle in drive with check engine light flashing. I feel I have to keep my foot on the accelerator to keep the engine from dying. After I take off from a stop the car is fine and drivability is excellent. The diagnosis is number 3 cylinder is misfiring. The mechanic installed a new spark plug and determined spark to the plug and it still shakes with lifter/tappet noise from engine. The next step will be to install a kit as it is called to deactivate the AFM. Kit comes with new cam & lifters, etc.

  8. #66
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    Re: Active Fuel Management

    Did you test drive it before you bought it? Did you buy it from a private person or used lot? Did the used lot have a warranty? Is it a dealer mechanic or independent?

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    Re: Active Fuel Management

    i had problems with my 2008 silverado with 136000 miles with the 5.3 AFM system and i had to replace it. it is called a (valve lifter manifold) item #555 and cost was 317 bucks at dealer. when it goes bad i never got a code other than P0300 which is random misfire with no exact cylinders posted. what happens is it starts ok but within 15 seconds or it starts running like its only running on 4cly, shaking, loss of power (with out it saying engine safe mode or reduced power) man i threw every part at it which i did not care because they should of been replaced 80,000 miles ago. but if this helps at all?? might want to have it tested or replace if its over 50,000 miles anyways. it took me 20 mins to take off with hand tools. people need to really read the manuals, most of the parts 99.9% should be replaced as general MAINT. anyways. electronics do not last, most moving or electrical parts will go bad, its just a matter of time. so if you can do it yourself? its well worth replacing everything! throttle position sensor is $44, throttle pedal is $78, cranks sensor is $48, cam sensor $54 these are all dealer prices and they are major components for the performance and maint of vehicle atleast its a place to look. DO NOT BUY ANY ELECTRONIC SENSORS FROM ANYWHERE BUT DEALER! I KNOW FROM EXPERIENCE. yes bought them from ebay, autozone and so on THEY ALL FAILED! and 360 bucks for my fuel pump is also worth it, i know it will get over 100,000 miles from the dealer. thanks

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