2007 retired Police Tahoe AFM disaster

[buddyhotrod]

2007 Tahoe with the 5.3 AFM motor.
83,000 miles


Was Hwy driving and it just started missing really bad

Chck engine light was flashing.

Cat smelled like eggs and was leaking fuel / oil out the tail pipe, also had steam coming out the tail pipe.

Serious kick in the gutt.

Why in the world would GM allow the AFM to be put into production I will never know.

My 2002 Tahoe has 260 on the odometer and has never had one problem.

 

[CobraKing]

Sorry to hear this. Have you or your mechanic diagnosed it as AFM or lifter failure?

 

[swathdiver]

Your description of events reads like a head gasket or cracked block/head failure. Remember to gut or replace the cats before completing whatever repairs are needed.

GM was forced to develop and implement AFM because of government regulations. Who we vote for does matter. The latest parts are far more reliable, the system received a major tweaking in 2011. If you source a junkyard motor, 2007-2009 will not have VVT, while the later ones will all have it.

Sure is a bummer man, we're here to help.

 

[buddyhotrod]

Your description of events reads like a head gasket or cracked block/head failure. Remember to gut or replace the cats before completing whatever repairs are needed.

GM was forced to develop and implement AFM because of government regulations. Who we vote for does matter. The latest parts are far more reliable, the system received a major tweaking in 2011. If you source a junkyard motor, 2007-2009 will not have VVT, while the later ones will all have it.

Sure is a bummer man, we're here to help.

Thank you and I appreciate your input.

Is it possible to drop a 6.0 or 6.2 motor in? Would the factory ecm work with a 6.0 or 6.2?

 

[swathdiver]

Yes, however you would need the donor engine's ECM or one programmed for it as those engines all have VVT.

The LY6 and L96 do not have AFM, while the L76 does. All are 6.0 Gen IV motors. The L92 and L9H do not have AFM, while the L94 does. All of these are 6.2 Gen IV motors.

 

[buddyhotrod]

Thank you for that.

I work for a municipality as a mechanic and was talking with some of the guys that work on the police cars.

They were telling me that my 2007 police Tahoe should have had the AFM disabled.

I’m going to pull the valve covers and look for loose rockers and kind of go from there, next pull the plugs.

I got my retired police Tahoe in August of 2018 and it had 81,000 miles on it, since owning in just 3 months I’ve complete 3 oil changes and always used the acdelco oil filter.
Now it has 83,000 miles.

Occasionally when it’s nice and warm I’ll floor it from a standstill up to 65 mph in hopes of blowing out any build up in the cats.

Otherwise I just kind of putt around in it.

I did drive it for about 15 miles on the highway until I could find a safe place to pull over.

It never got hot doing so, and the oil looks really good with no coolant or fuel in the oil and the coolant level is still full.

Just keeping my fingers crossed that the motor is not hosed.

 

[swathdiver]

Hoping for the best! The most common failure is a collapsed lifter or a bad VLOM solenoid. Even if the PD disabled AFM, they likely turned it off in the tune and did not physically remove it. It's still there and the lifters can still fail.

The condition of the fluids looks promising, you're on the right track to discovering the problem. However, a Tech2 or bi-directional scan tool would make short work of diagnosis.

 

[buddyhotrod]

Collapsed Lifter for exhaust valve on #4.

Pulled the intake and was able to get the lifter back in place with little tap trick.

The exhaust valve rocker was completely loose.

Now just need to decide on a AFM OBD disabler.
Also waiting on new gaskets.

Amazon has a AFM disabler that plugs into the OBD but Not sure how that will work when it comes time for the States OBD inspection.

Perhaps a OBD splitter would work.

Need to do some more reading.

Also open to any tips.

 

[buddyhotrod]

The spark plugs have about 1000 miles on them.

Anyone think they look odd?

 

[iamdub]

Collapsed Lifter for exhaust valve on #4.

Pulled the intake and was able to get the lifter back in place with little tap trick.

The exhaust valve rocker was completely loose.

Now just need to decide on a AFM OBD disabler.
Also waiting on new gaskets.

Amazon has a AFM disabler that plugs into the OBD but Not sure how that will work when it comes time for the States OBD inspection.

Perhaps a OBD splitter would work.

Need to do some more reading.

Also open to any tips.

A plug-in AFM disabler won't affect anything with your inspections. Just remove it before going to get the inspection so they can plug their computer in the ALDL port then plug it back in when you leave. Since you asked for tips, I'd say that since you're already that far into it, you may as well pop off the heads and valley cover and replace the lifters and VLOM ("valley cover") with the newer/updated designs. If you wanna go a few steps further and never have another AFM-related failure, replace the AFM parts (lifters, VLOM and cam) with their non-AFM counterparts, then get a tune to turn off AFM. Of course, this is much more involved. But, just replacing the AFM lifters isn't much more work than where you currently are. That lifter collapsed once and I don't see what would stop it from happening again soon after you put it all back together and start it.

The spark plugs have about 1000 miles on them.

Anyone think they look odd?

Considering the way the PCV and AFM system dumps oil into the intake and combustion chambers, I'd say the plugs look about as expected. You may wanna add the updated LH valve cover to your parts list for it's revised PCV design.

 

[buddyhotrod]

Cool

Thank you for the information.

From what I understand and from looking at the solenoids on the current AFM valley / intake valley. Looks like the way the motor works is the oil pressure is always there in the valley veins and only when the ECM says to the solenoids "hey close" / time to go into V4 mode only then the oil pressure is cut off to the lifters to collapse them and allow the valves to stay closed allowing the motor to be running on the the remaining live cylinders.
Im going to do some reading on the updated LH valve cover. Not sure what the update is and if I could replicate the update on my own.

Ive thought hard about the complete AFM delete with the cam and new lifters, Ill keep that in mind for sure.


Feel like if I am going to pull the heads and do all of that then the thought of twins comes to mind.



Amazon has a complete twin set up for 2200 dollars.

That would be so cool.

 

[CrashTestDummy]

First you ask if the AFM delete module will affect inspections, now you're planning on a twin-turbo kit? That WILL affect inspections, unless the kit has a CARB cert.

You'd probably be much better off with a DOD-delete kit from a good vendor like Texas Speed, or others. That way, you can set it and forget it, and no one will be the wiser, except for maybe the light lope in the idle. ;-)

 

[blackjack]

Hey Y'all,
When my 2008 finally gave up (Even after dealer AFM rebuild), I went with Comp Cam etc..and all LS6 stuff etc.. did heads, bypassed cats, custom tune; all easy in the driveway and truck is dynamite.
The dealer rebuild didn't last 30,000 miles, due to fact that dealer ignored the upgraded TSB fix and PPV Program. (That dealer is gone and not GM's fault lol)
In any event, truck is GREAT that way heading for 300k!
By the way, if anyone is having issues and wants an L77 with fresh beefy rebuilt 6L80 and all computer and elec from my front frame damages personal 2012 PPV 6.0 Caprice, get hold of me.. good swap!
Have fun, gotta go to work...
M

 

[89Suburban]

Amazon has a AFM disabler that plugs into the OBD but Not sure how that will work when it comes time for the States OBD inspection.


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I bought a used Range Technology AFM Disabler off a seller on Ebay and saved a few bucks and it works fine. I unplug it when it goes in for inspection.

 

[swathdiver]

From what I understand and from looking at the solenoids on the current AFM valley / intake valley. Looks like the way the motor works is the oil pressure is always there in the valley veins and only when the ECM says to the solenoids "hey close" / time to go into V4 mode only then the oil pressure is cut off to the lifters to collapse them and allow the valves to stay closed allowing the motor to be running on the the remaining live cylinders.

Go the GM Heritage Center and download the restoration kit for the Tahoe or Suburban. It explains the operation of the AFM system in detail and will complete what you've written about above.

https://www.enginebuildermag.com/2012/03/rebuilding-gms-4-8-5-3-and-6-0l-gen-iv-engine/

Go to that link and download the pdf there, lots of good reading too!

 

[Ron C]

ok,

might be a little late to "chime in" ... but what is AFM?

Ron

 

[swathdiver]

...but what is AFM?

AFM aka Active Fuel Management. It's the system by GM that drops the motor into V4 mode to increase fuel economy.

This system is used on the Gen IV and Gen V engines. The latest motors in the new pickups use Dynamic Fuel Management, all of the cylinders have the ability to be shut off in any combination, not just 1, 4, 6 and 7 at the same time.

 

[Ron C]

AFM aka Active Fuel Management. It's the system by GM that drops the motor into V4 mode to increase fuel economy.

This system is used on the Gen IV and Gen V engines. The latest motors in the new pickups use Dynamic Fuel Management, all of the cylinders have the ability to be shut off in any combination, not just 1, 4, 6 and 7 at the same time.

Ah.. ok. mine does that, didn't know it was called AFM (2013, GSA/SSV)

Ron

 

[CobraKing]

I bought a used Range Technology AFM Disabler off a seller on Ebay and saved a few bucks and it works fine. I unplug it when it goes in for inspection.

Got really lucky and managed to grab one off a kid local to me the other night. Amazing part - not having that V4/V8 shift really 'transforms' the vehicle.

 

[CrashTestDummy]

Ah.. ok. mine does that, didn't know it was called AFM (2013, GSA/SSV)

Ron

AKA DOD (Displacement on Demand).