2012 Yukon Denali XL with 6.2L and 6L80E at 172000 miles. Stalls in drive while cold

[testdepth]

The truck sat all night and today until 5pm when we got in it to drive up the road. Went two blocks at 15mph engine temp about 180. Foot on gas and in drive the engine starts surging and the RPMs run up to about 1500 and down to below 500 and back up. As I cruise to a stop at the light and still in drive I watch the RPM gauge drop to zero and the engine dies. I shifted to park and restarted the engine no problem. We kept driving and no more problems after engine was at normal 210F temp. No codes and no check engine light. Definitely happens when the engine is cold. After the engine is at normal temp 210F I have no issues. Have had this problem for a year. What would cause this to happen when the engine is cold?

 

[movietvet]

A year? Really? Had any tech/shop look at it and if so, what did they say? If not....I want to know how old plugs/wires are? Last time cleaned the MAF and throttle bore? But, what I suspect, especially if you can count on it doing this when engine is cold, hook up a fuel pressure gauge and have a long enough hose to run out of the back of hood and tape to w/s and see if loses fuel pressure when happens.

 

[testdepth]

Yes a year of this random issue. I took it to a local GM dealer and had their senior tech look at this (30yrs experience). He used his scan tool and found no codes or anything obvious. He checked for any updates available for the ECM and the rest of the systems but all were up to date. He suggested a bad ground somewhere and I would have to leave the truck with him for 2wks. We are the 2nd owner of this truck and have owned it for about 10yrs. I have not had problems until last year (the year of the Yukon). I have a TOPDON ARTIDIAG900 bidirectional scanner.
For the last 6 months:
New AC Delco fuel pump
New throttle body (performed relearn)
New MAF sensor (Delphi replaced two days ago before this problem happened again)
New plugs
New coils
New crank sensor
New coolant temp sensor (actually crumbled apart in my hand when I went to check it)
New fuel injector sensor
New negative battery cable set
New braided engine ground from the block to the driver side firewall
New EVAP canister
New EVAP purge solenoid
New MEGA fuse
New oil pressure sensor and the filter under it (FLEX engine)
New AFM delete made by BOOST and plugs into the OBD port (V8 all the time)

All of this has been done but the problem persists. No engine misfires (none shown on scan tool). I have hooked up a fuel pressure gauge and pressures are all in spec while in park and driving down the road. No DTC codes set and no check engine light. This problem happens when the engine is cold and the truck is being driven. I start it up cold in my carport and let it runs with no issues as it warms up and idles just fine. I just went out and started the engine and sprayed carb cleaner all over the intake manifold and no change so no vacuum leak.

I have not replaced or checked:
Plug wires
Original O2 sensors (4)
Original VVT solenoid
Original CAM sensor
Original intake gasket
All grounds
Transmission

 

[mrrsm]

Sometimes ...the *Startling Stall* can be symptomatic of a Failing Ignition Switch... and since you used the expression "WE"... it could be caused by the pendulum-like action of a Wife's Heavy Laden Key-Chain responding to the gyrations and motions cause by the Angular Momentum of Starts, Stops and Left & Right Turns...variably tugging upon it... and at some "Key" positions...managing to break the expected solid Electrical Connections afforded by the IGN Switch.

This will probably turn out to be nothing... but just in case it is involved... Visit THIS Thread in another Site Forum to bone up on the topic, At this point in your investigation...looking at things as arcane as this might prove useful under the circumstances.

2012 Yukon Denali with 6.2 engine. Truck stalled and shut off while driving. 169000 miles.

Before you throw parts at it, I would look into a data logger or bluetooth dongle and data logger app. Have your wife tell you the exact time it happens and see what the logger shows. I would hesitate to replace any OEM part with something new (even OEM replacement). You could be introducing a...

www.theoutdoorstrader.com

Also...as per @movietvet 's observation about the MAF issues... I would re-visit the MAF with CRC MAF Spray Cleaner -=ONLY =- and a Tooth Brush and Clean It AGAIN.... Especially if the Air Filter was NOT changed when the New MAF was installed as Chunks of Junk can constantly break loose from a compromised Dirty Air Filter or Inlet Tube that is left open to ambient, unfiltered air ...and collect HERE on these Two Tiny Resistors (Red Arrows) :



You know this already, but it deserves repeating for those who need to know it:

The Mass Air Flow Sensor (MAF) includes the means to both measure the incoming Air Temperature AND IT WEIGHS every Gram of Air coming inside the Throttle Body so the Air to Fuel Ratio remains as close to 14.7 to 1 as possible ALL the Time...otherwise, the PCM won't understand and...THE ENGINE CAN SUDDENLY STALL or at the very least...cause it to drop into LIMP MODE (Reduced Power)....Very, Very SUDDENLY.

One Last Thought... Check the MAF Harness to CONFIRM a reliable 5 Volt DC Sensor Reference Voltage as THIS failure point can cause the MAF to fail if the wiring harness between the PCM and the MAF is Sketchy using this reference voltage can also cause the Engine to Stumble and Stall.

Suspect a possible Rodent Depredation Under Hood Problem and scour the harnesses and Plastic Connectors with a Bright Flashlight, Eye Protection, N-95 Mask and M11 Nitrile Gloves while searching for any signs of Chewed Wiring, Mouse Feces and Rodent Nesting artifacts. The protective gear can keep you from becoming infected with Rodent Borne HANTA Virus carried on Airborne Dust covered with Virus particles that can infect the lungs. It has a 40% Mortality Rate...so BE CAREFUL!

 

[testdepth]

My Yukon is fixed. The connector to my new coolant temperature sensor was bad causing false readings used for fuel trims. New connector installed and no more problem.

 

[movietvet]

I see you had already replaced the sensor and then I saw the comment below....

"actually crumbled apart in my hand when I went to check it"

At that point, I would bet that you used any replacement sensor, other than a Genuine GM sensor....

Because the Genuine GM sensor recommends replacing the connector when replacing the sensor...

More Information for GM GENUINE 2134333

 

[testdepth]

I used a GM sensor when I replaced it last year. The connector was good back then but the old GM sensor crumbled in my hand. Most likely because ignorant GM engineers installed the sensor a few inches from the driver side exhaust manifold without using a heatshield.

 

[movietvet]

I used a GM sensor when I replaced it last year. The connector was good back then but the old GM sensor crumbled in my hand. Most likely because ignorant GM engineers installed the sensor a few inches from the driver side exhaust manifold without using a heatshield.

Are you saying that the GM sensor you used, last year, did not recommend the new connector, when you bought it? Or the store employee did not recommend it? Or the GM sensor you bought was an AC Delco?

Also, if you saw the "close to exhaust heat problem", did you then use a flexible heat shield of some sort to protect it?

If not then, will you do the protection now?

I gotta say, if I went to remove/install a coolant temp sensor and it crumbled in my hand, I would have done the connector at the same time and that may well be why GM says it should be replaced at the same time.

Don't get me wrong, I am glad it is fixed, but you said yourself that it crumbled in your hand. The next statement after the "crumbled" statement, is that you did the connector, for good measure. Again, especially if the Genuine GM application calls for the new connector.

 

[testdepth]

The sensor I bought was AC Delco and I will install a heatshield. The sensor crumbled and the electrical connector looked fine with no signs of being bad.

 

[movietvet]

The sensor I bought was AC Delco and I will install a heatshield. The sensor crumbled and the electrical connector looked fine with no signs of being bad.

I truly understand, The ACD sensor does not call for the connector replacement, at RA, but the Genuine GM sensor does. Again, strictly, IMO, if I unplug a connector and the sensor that connector is plugged in to, starts crumbling as I remove it, I am gonna replace any connector.

BUT, I am glad it is fixed. I bet you are too.

One thing I learned while in shops for 40+ years, if I have to stand behind the work/parts, I am gonna spend "other people's money" all day long.