Ponch
TYF Newbie
It's a classic. Great movie.
AFM yay or nay?
- Thread starter PPVHOE12
- Start date
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It's a classic. Great movie.
YukonCrazy
Full Access Member
When I first bought the Yukon, I really didn't even notice when it switched between V8 and V4 mode. In the past couple years, it feels very obvious when it switches back and forth.
Yesterday I was on my way to work in traffic and I was just coasting down hill with no foot on the gas going like 20 miles an hour and I noticed it was in V4 mode. You could feel the difference in addition to the dash display. Doesn't sound right for that to be in V4 mode at 20 MPH.
Yesterday I was on my way to work in traffic and I was just coasting down hill with no foot on the gas going like 20 miles an hour and I noticed it was in V4 mode. You could feel the difference in addition to the dash display. Doesn't sound right for that to be in V4 mode at 20 MPH.
gooffeyguy
Tom
When mine was enabled it would only go into v4 mode when I let off the gas and was coasting. The slightest touch of the gas pedal would go back to v8 mode.
I don't see how this helps fuel economy any. I would've thought it would stay in v4 mode while cruising at speed on the highway, but it didn't.
2001 Yukon SLT
2012 Yukon Denali XL
2011 Yukon Denali RIP 5/20/18
I don't see how this helps fuel economy any. I would've thought it would stay in v4 mode while cruising at speed on the highway, but it didn't.
2001 Yukon SLT
2012 Yukon Denali XL
2011 Yukon Denali RIP 5/20/18
avalonandl
Full Access Member
Well there are AFM failures that are NOT based upon poor oil maintenance.
YukonCrazy
Full Access Member
So how does one know if you ha e the updated valve cover? Can you tell from looking at it externally?
iamdub
Full Access Member
Unfortunately, no. But, at least removing the cover is only a 10-20 minute task.
There are some pics on the internet saying you can ID it by the design of the PCV nipple at the back of the cover. This is only half true. The newer engines (2010+, I think) had a different PCV hose design and they, of course, had the updated PCV baffle. My '08 had the older PCV nipple so I assumed it had the older PCV baffle design and so I bought a newer cover. I went to replace mine and found that it had the updated baffle design. Check yours and if it's the older baffle design, order the new one. Disregard the PCV nipple type because you should have a catch can, anyway, and the rubber hose from that will fit either nipple. If you don't have a catch can, then shame on you.
They're under $20 on Amazon for a pretty darned decent one and you can get a stainless scrub pad for $1 from the Dollar Tree and probably other similar discount/dollar stores.
gooffeyguy
Tom
Personally I think having a pcv hose on the rear of a valve cover is a very bad design. Engines don't sit level and have a slight rearward angle. Oil will naturally go towards the back of the top of the head. The port should be more towards the front, if not in the front.
2001 Yukon SLT
2012 Yukon Denali XL
2011 Yukon Denali RIP 5/20/18
2001 Yukon SLT
2012 Yukon Denali XL
2011 Yukon Denali RIP 5/20/18
iamdub
Full Access Member
This is the purpose of the baffle. The port is at the rear but it's shielded by the baffle which has an opening towards the front. As I understand it, the design flaw in that was the location of the opening. It was located right over a rocker and the oil flinging up from it went straight through the hole, allowing the baffle to collect oil and flow to the back where some would be sucked up by the PCV port. The updated design has a larger hole that has been relocated more forward.
A baffle is needed regardless so the port isn't directly in the same space as the rockers and flying oil. If the port was already at the front then the baffle opening would be at the rear, but that's where most of the liquid oil will be due to the engine's angle and normal direction of acceleration.
gooffeyguy
Tom
The baffle would be less relevant if the port was located correctly.... Lol
I run custom valve covers on my 302 mustang (built, supercharged 600hp motor) that have vacuum ports in the front. I use a vacuum pump hooked to thes ports to maintain a constant 8-10" of vacuum in the crankcase. The output of the vacuum pump enters a baffled catch can with a breather/filter on top. There is very minimal oil collected in the catch can.
2001 Yukon SLT
2012 Yukon Denali XL
2011 Yukon Denali RIP 5/20/18
I run custom valve covers on my 302 mustang (built, supercharged 600hp motor) that have vacuum ports in the front. I use a vacuum pump hooked to thes ports to maintain a constant 8-10" of vacuum in the crankcase. The output of the vacuum pump enters a baffled catch can with a breather/filter on top. There is very minimal oil collected in the catch can.
2001 Yukon SLT
2012 Yukon Denali XL
2011 Yukon Denali RIP 5/20/18
iamdub
Full Access Member
I never said it wasn't a band-aid to their design flaw!
You have any pics of your custom valve covers, preferably the insides? I'm curious if there's any further, but simple aftermarket re-engineering that can be done.
