2012 Yukon 1500 XL Denali 6.2L while driving truck shudders, rpms run up and down until engine dies. Update at #44

[swathdiver]

This truck jerks, hesitates, RPMs run up and down and acts like it wants to die. I'm thinking it's something to do with the AFM shifting back and forth from V8 to V4.

And if you drive in M5 do these symptoms still happen?

M5 disables AFM.

I know that you recently changed the spark plugs, did the old ones look about all the same? If not, have you pulled the new ones to see how they're looking?

Do the rpms fluctuate at a steady speed on the highway? If so, that's usually the sign of a failing torque converter clutch. Once it goes, it contaminates the entire transmission and cooling system with debris.

 

[Doubeleive]

it can be figured out your just going to have to do the equivalent of a EKG, connect a fuel pressure gauge and stick it up thru the hood opening, connect the scanner and start monitoring all the live data, knock retard, coils, injectors, 02 sensors, misfires, map sensor, ambient temperature, etc.
sometimes the problem is enough to feel but not enough to throw a code until it gets to a XX count or fails 3 times in a row/drive cycle.
new parts can be faulty and some aftermarket parts are well known to often fail in short order.
just like you discovered with your brand new spark plug....

 

[testdepth]

Part of the reason I was thinking AFM, a difference between how you drive vs. your wife.
You have to be really light on the throttle.. just barely cruising..

But since you have been testing when it goes into V4 mode, I suspect that's not really it.

You mentioned O2's, might want to pull those up on your scanner.
I would say something should show up SOMEWHERE while scanning parameters, sounds like it maybe intermittent.. but usually those will leave some code?

Your spark plugs... were they from amazon? Just because I've heard a couple stories..

The reason I believe it is the AFM is that I have ruled everything else out. From what I've read a bad solenoid in the Lifter Oil Manifold Assembly will cause the problem I'm currently having. In theory if I disable that, then my problem goes away. Or I will have to spend about $300 for a new Lifter Oil Manifold Assembly. This truck only goes into V4 when I lift my foot off the gas pedal and decelerate.

I have no codes for the O2 sensors and on the scanner they look to be functioning correctly.

Yes the iridium plugs came from Amazon however out of the 8 plugs only one was bad and I replaced that with an NGK.

Thank you

 

[testdepth]

And if you drive in M5 do these symptoms still happen?

M5 disables AFM.

I know that you recently changed the spark plugs, did the old ones look about all the same? If not, have you pulled the new ones to see how they're looking?

Do the rpms fluctuate at a steady speed on the highway? If so, that's usually the sign of a failing torque converter clutch. Once it goes, it contaminates the entire transmission and cooling system with debris.

We have not driven that much in M5 but the driving we have done has been without any problems. I have ordered an AFM disable device to insert in the OBD port so my wife doesn't have to remember to keep placing the truck into M5 in order to disable the AFM.

All of the old plugs looked exactly the same.

RPMs only fluctuated while this problem was happening and not at HWY speeds.

 

[testdepth]

This is the AFM disabler I'm using because it's made in America!

Boost AFM & DFM Disabler - Save Your Lifters - Made in USA

Prevent lifter failure and improve performance with our Boost AFM & DFM Disabler for GM vehicles. 100% Made in the USA!

boostafmdisabler.com

 

[rsharger]

2012 Yukon 1500 XL Denali 6.2L. In park and started but get check engine, Stabilitrak Disabled, Traction Control Disabled, Service Stabilitrak

I have been having issues with this truck for the last month or so. 170000 miles on it. First started with stalling and shutting off while driving and that's resolved (crank sensor). Then in park and at idle after about 10 minutes the engine would completely shut off (EVAP purge solenoid). Then while driving at 45 mph the truck would act like it was going to stall, jerk back and forth and RPMs would go up and down but not stall completely. I think this jerking is resolved now.

I have replaced the following and spoke to a guy that's been a mechanic on GMs at the local dealer for 30yrs.
New AC Delco fuel pump
New MAF sensor
New crank sensor
New negative battery cables and cleaned contacts to bare metal
New coil packs
New iridium plugs
New throttle body
New oil pressure sensor and filter
New EVAP purge solenoid
New EVAP canister

All of this is replaced and all relearn procedures that were needed are done. The GM mechanic looked for any updates to this truck's ECM and other sensors but there were none called out.

Now just an hour ago this happens: My wife drove to the store with no problem. She then got back in to come home and tried to start it. While parked the check engine comes on, Stabilitrak Disabled, Traction Control Disabled, Service Stabilitrak all come on and engine runs like its missing. She drove it home this way.

I put my scanner on it and it shows P0300 code. I brought up the misfire screen and shows cylinder 6 is misfiring. I just replaced all 8 coil packs so its possible one went bad.

I'm not sure why the stabilitrak and traction control would come on and then say to service them?

My 2012 Suburban had an intermittent issue just like yours. It was the steering wheel position sensor. I noticed that's one thing you did not mention on your list of parts. Ron.

 

[rsharger]

2012 Yukon 1500 XL Denali 6.2L. In park and started but get check engine, Stabilitrak Disabled, Traction Control Disabled, Service Stabilitrak

I have been having issues with this truck for the last month or so. 170000 miles on it. First started with stalling and shutting off while driving and that's resolved (crank sensor). Then in park and at idle after about 10 minutes the engine would completely shut off (EVAP purge solenoid). Then while driving at 45 mph the truck would act like it was going to stall, jerk back and forth and RPMs would go up and down but not stall completely. I think this jerking is resolved now.

I have replaced the following and spoke to a guy that's been a mechanic on GMs at the local dealer for 30yrs.
New AC Delco fuel pump
New MAF sensor
New crank sensor
New negative battery cables and cleaned contacts to bare metal
New coil packs
New iridium plugs
New throttle body
New oil pressure sensor and filter
New EVAP purge solenoid
New EVAP canister

All of this is replaced and all relearn procedures that were needed are done. The GM mechanic looked for any updates to this truck's ECM and other sensors but there were none called out.

Now just an hour ago this happens: My wife drove to the store with no problem. She then got back in to come home and tried to start it. While parked the check engine comes on, Stabilitrak Disabled, Traction Control Disabled, Service Stabilitrak all come on and engine runs like its missing. She drove it home this way.

I put my scanner on it and it shows P0300 code. I brought up the misfire screen and shows cylinder 6 is misfiring. I just replaced all 8 coil packs so its possible one went bad.

I'm not sure why the stabilitrak and traction control would come on and then say to service them?

(btw I was referring to the Stabilitrak/ABS issue etc....)

 

[testdepth]

I installed the AFM disable and we just drove 8 miles roundtrip in traffic with no problems at all. V8 all the time.

We shall see with more miles placed on this truck but I 100% believe the hesitating, jerking and near stalling problem was the AFM system and some glitch between the constant switching back and forth between V8 and V4 at low in town speeds.

 

[swathdiver]

I installed the AFM disable and we just drove 8 miles roundtrip in traffic with no problems at all. V8 all the time.

We shall see with more miles placed on this truck but I 100% believe the hesitating, jerking and near stalling problem was the AFM system and some glitch between the constant switching back and forth between V8 and V4 at low in town speeds.

If that's the case, your VLOMs solenoids are the problem and are out of time. Time for a new one or just get the truck tuned properly and disable it.

 

[wziegmond]

2012 Yukon 1500 XL Denali 6.2L. In park and started but get check engine, Stabilitrak Disabled, Traction Control Disabled, Service Stabilitrak

I have been having issues with this truck for the last month or so. 170000 miles on it. First started with stalling and shutting off while driving and that's resolved (crank sensor). Then in park and at idle after about 10 minutes the engine would completely shut off (EVAP purge solenoid). Then while driving at 45 mph the truck would act like it was going to stall, jerk back and forth and RPMs would go up and down but not stall completely. I think this jerking is resolved now.

I have replaced the following and spoke to a guy that's been a mechanic on GMs at the local dealer for 30yrs.
New AC Delco fuel pump
New MAF sensor
New crank sensor
New negative battery cables and cleaned contacts to bare metal
New coil packs
New iridium plugs
New throttle body
New oil pressure sensor and filter
New EVAP purge solenoid
New EVAP canister

All of this is replaced and all relearn procedures that were needed are done. The GM mechanic looked for any updates to this truck's ECM and other sensors but there were none called out.

Now just an hour ago this happens: My wife drove to the store with no problem. She then got back in to come home and tried to start it. While parked the check engine comes on, Stabilitrak Disabled, Traction Control Disabled, Service Stabilitrak all come on and engine runs like its missing. She drove it home this way.

I put my scanner on it and it shows P0300 code. I brought up the misfire screen and shows cylinder 6 is misfiring. I just replaced all 8 coil packs so its possible one went bad.

I'm not sure why the stabilitrak and traction control would come on and then say to service them?

check what transmission you have in vehicle. certain tecm Trans control modules have reed valves that blow out. causing the mentioned symptoms.

 

[swathdiver]

check what transmission you have in vehicle. certain tecm Trans control modules have reed valves that blow out. causing the mentioned symptoms.

6L80.

 

[Badge]

I’m surprised no one has brought up checking the suspension first at 170K miles. Or I missed it. The ESC(m) will shut down the system into limp mode, which is what this sounds like. Crazy dumb feature and dangerous as it happened to me driving down the road. I have the 2013 Yukon xl Denali. First time was simply a dirty throttle body; cleaned it out and all fine. BTW, just buy a new one with throttle sensor (and relearn) vs cleaning it at that mileage. Second time was front suspension; lots of variables to go wonky with Z55 anyway or if you have Z95 RPO. The ESC won’t always throw a code as I believe it goes through the BCM; so if you have a bad ESC module (above fuel tank) or errant code that’s doesn’t repeat a lot, then you’ll have to test it separately as they’ll be little or no indication it’s bad, especially if the back air shocks still work (but front are bad). Need to look at dampeners, etc, voltages and make sure things are working or not. If it senses your shocks aren’t sufficient, it will shut it down. My 1.5cents, look at suspension system next since misfire was fixed. Simplistic cause to begin with IMO and experience. Certainly not a professional. If you have a tech2, you can clear the Stabilitrak codes and warnings, try ALC to get things back on track. I’ve had AFM disabled (just diablo tune) for years and no issues, btw. I don’t see AFM hurting anything now that misfire was addressed if it was on one of those cylinders. Good luck.

 

[testdepth]

On my truck the problem was in the AFM system while it would switch between 8cyl and 4 cyl at speeds under 50mph. It would switch from V8 to V4 only on deceleration.

My wife just drove this truck 40 miles to her dentist with the BOOST AFM disabler engaged and she had no problems at all with the engine. V8 all the time.

AFM disable for the fix!!

 

[testdepth]

My wife just returned from the dentist. 80 miles roundtrip in stop go and HWY traffic with no problems. The problem with this truck was the AFM being AFU. AFM is now disabled and no more problem.

 

[swathdiver]

My wife just returned from the dentist. 80 miles roundtrip in stop go and HWY traffic with no problems. The problem with this truck was the AFM being AFU. AFM is now disabled and no more problem.

Sounds like the problem has been identified and solved. Consider updating the title.

For a more permanent "repair", I would suggest getting an actual tune. Did this to mine back in 2017.

 

[testdepth]

Sounds like the problem has been identified and solved. Consider updating the title.

For a more permanent "repair", I would suggest getting an actual tune. Did this to mine back in 2017.

What do you mean by "actual tune". From what I have read doing an actual AFM delete versus the AFM disable costs a little under $2000. Are you talking about a delete?

 

[swathdiver]

What do you mean by "actual tune". From what I have read doing an actual AFM delete versus the AFM disable costs a little under $2000. Are you talking about a delete?

Your OBDII device disables AFM. A tune will reprogram the computers to turn off AFM and its related codes. The tuner can also tune the engine and transmission for better performance and durability to your liking.

While uncommon, those OBDII adapters fail and may prevent you from pulling live data with a scan tool or phone app.

 

[testdepth]

Your OBDII device disables AFM. A tune will reprogram the computers to turn off AFM and its related codes. The tuner can also tune the engine and transmission for better performance and durability to your liking.

While uncommon, those OBDII adapters fail and may prevent you from pulling live data with a scan tool or phone app.

What tuner are you recommending and what is the cost of doing that?

 

[swathdiver]

What tuner are you recommending and what is the cost of doing that?

BlackBear Performance. @BlackBearPerf

Not sure about the latest costs, did two over the years. Still one to go!

 

[Fless]

https://www.diablewtune.com/ is also a somewhat popular tuner.