2007 Yukon 6.2 stalls/won’t start when hot

[Campie]

Actually yes, a failing battery can cause this, along with all sorts of other issues. It's a roll of the dice to predict what it will react with. Simple enough, most auto parts stores will load tested in the car for you. They will also check your charging system for free.

I can't remember all the previous six pages of posts..... Did you verify the brake booster doesn't have a huge vacuum leak internally?

Nice, I’ll get the battery tested. Did not check the brake booster yet. I’ll track down your post and figure out how to check the vacuum. Not sure if putting the break on is consistent with the engine dying, but we will talk about that and let you know. Seems like it might be. Odd though because usually we get off the highway, stop at the top of the exit ramp, continue on For another few hundred yards and then stop again to turn or for traffic. That’s when it dies.

 

[rdezs]

That doesn't really sound like the brake booster then. Besides checking if it holds a vacuum, many times while you're sitting there stopped holding the brake down you can hear a little hissing sound if it's got a good leak.

 

[dkad260]

Here's another thought since it happens on decel.

Something I notice when driving and monitoring the Torque Pro app, when decelerating, there's a good bit of Short Term Fuel Trim fluctuation....like 15%.

I wonder of your injector(s) might have a fault and you are getting a very rich mixture on one or more cylinders and the plug(s) are temporarily fouled or wet.

Next time it happens, try a cleared flood mode when starting by holding the gas pedal to the floor while cranking.

Which leads me to ask, how old are your spark plugs, and are they OE AC Delco?

Once a plug is fuel fouled, it won't be right again if left untouched. Maybe they are old and have been fouled before, or the wrong plugs.

 

[Campie]

Interesting idea but there’s no sputtering or odd behavior. It runs great and is powerful and crisp to accelerate, but then the engine just stops… Always slowing down after highway speed, pulling a small camper.

Plugs are 6 months old and good quality - not sure what but our local shop uses quality parts but I’ll check the brand he used.

 

[Campie]

Also, we have tried the cleared flood process and it does not help.

Finally, though, I have some additional information! The battery that was in it was bad, not horrible but it would drop to 11.5 under stress. So battery is replaced. We’ve also figured out a little bit more about how to use the scanner tool.
At idle: The MAF is right around five, which I think is where it should be. The fuel trims are very small and mostly positive, but I don’t know enough about that sort of thing to describe more. Haven’t been able to look at the fuel trims while driving because I am by myself most of the time.

There is an EBCM error, control, module communication bus off. That error could simply be me not knowing how to use the scanner but if not, how do I fix that?

There is a low-voltage on TFP switch #5 circuit. How do I fix that?

I noticed on the scanner there is a fuel shut off on deacceleration. What is that controlled by? Is that a relay that I could replace? To us, fuel shut off on deacceleration seems like exactly what the problem is!

Also, the auto ride suspension has been removed from the vehicle so every time it starts, we get a check, suspension error and of course, there are all sorts of notations on the scanner about the ESC. Is there a fuse or relay or something I could pull to convince the car this is not a problem?

We have not had time to test it under load. The other thing we have not done yet is replace the fuel sensor relay although I have it and will replace it before we test the vehicle. Thanks guys!

 

[Fless]

It might be helpful to post the actual DTCs you're seeing with your scanner. Descriptions alone are sometimes vague and can lead to the wrong path.

 

[SpareParts]

Using your scanner what does the MAF read when running in park hot idle?
Not set in stone, but the general rule is. It should be reading about the same as engine displacement. In your case about 6.2g/s
Im guessing if it's under 6g/s you have a vacuum leak that gets worse the more the engine gets heat soaked.
Check the PCV hose connection at the back of the DR side valve cover. The vent hose connection at the front of the RT side valve cover and the seal around the oil fill tube.
Just fixed almost the same problem on a friends Yukon. His would die like yours but start right back up.

Also a low/bad battery will give you all kinds of codes and problems. Once replaced they will still be their till cleared. If they come back, then you might have a problem.

 

[Fless]

Check the PVC hose connection at the back of the DR side valve cover.

"PCV" Positive Crankcase Ventilation

 

[Campie]

It might be helpful to post the actual DTCs you're seeing with your scanner. Descriptions alone are sometimes vague and can lead to the wrong path.

Ok, I tried to type the exact words off the scanner but i can post pix later.

 

[Campie]

"PCV" Positive Crankcase Ventilation

And where is that? It’s a hose on this car I think. I’ll post a pic.

 

[Campie]

Using your scanner what does the MAF read when running in park hot idle?
Not set in stone, but the general rule is. It should be reading about the same as engine displacement. In your case about 6.2g/s
Im guessing if it's under 6g/s you have a vacuum leak that gets worse the more the engine gets heat soaked.
Check the PVC hose connection at the back of the DR side valve cover. The vent hose connection at the front of the RT side valve cover and the seal around the oil fill tube.
Just fixed almost the same problem on a friends Yukon. His would die like yours but start right back up.

Also a low/bad battery will give you all kinds of codes and problems. Once replaced they will still be their till cleared. If they come back, then you might have a problem.

That MAF at 5 or a bit higher was after running for about 10 minutes. I’ll get more info when it’s for sure hot.

 

[SpareParts]

PVC=PCV Fixed!
Thanks Fless

 

[pastormatt]

I had the same problem with my 2007 Yukon Denali. After about four months of trying everything, I discovered it was the purge solenoid. It’s not closing when you’re coming to a stop or idling down. It’s like it’s flooding the engine with gas vapor.

 

[B-train]

I've found this thread interesting as my 2008 Denali has recently started being a PITA for me as well. It happened once in June after the A/C was on in hot weather, pulled off the freeway and turned into the park and ride. Engine almost stalled - dropped ro 300 rpm (kinda galloping) like it was out of fuel. I pumped the gas pedal in neutral and it eventually cleared up and revved up to 2500 and then seemed OK. CEL with a throttle body code and crank sensor correlation. Replaced crank sensor and thought all was well.....

It was.......until I go on a work trip to PR and it does the same thing to my daughter after slowing down for a construction zone (A/C on, hot out again). She calls me and I walk her through it and it all seems OK. Wife drives it the day she's supposed to meet me in PR and it stalls on her - same exact scenario. I had her hold her foot to the floor and crank it to see if it was flooded - didn't seem to help. I then had her open the hood to let out excess heat and it ended up restarting about 20 minutes later and I advised to drive straight home, no air conditioning, and park it.

Long story, but thanks to this thread, I have some ideas. At first I was thinking maybe cam sensor or throttle body flaking out with the excess heat coming through the grill from running the A/C. I replaced the purge valve and few years back with a GM part - wasn't thinking an OEM part would fail so soon, but its possible. My plan when I get home is to hook up my HP Tuners computer and run a data log to try and repeat the scenario and capture some data to share here.

As far as I know, no CEL came on either time for them which lends to the purge solenoid. I think I got the CEL when I was trying to keep it running like a 1978 Chevy pickup and it didn't know what the F was happing to it. LOL

Keep us posted on what you eventually find yours to be. Good luck!

 

[donjetman]

@B-train
Have these 2 Technical service bulletins been done?
https://static.nhtsa.gov/odi/tsbs/2012/MC-10138192-9999.pdf
and
https://static.nhtsa.gov/odi/tsbs/2014/MC-10114272-9999.pdf

 

[B-train]

@B-train
Have these 2 Technical service bulletins been done?
https://static.nhtsa.gov/odi/tsbs/2012/MC-10138192-9999.pdf
and
https://static.nhtsa.gov/odi/tsbs/2014/MC-10114272-9999.pdf

Thank you for those! The oil consumption one doesn't affect mine, it doesn't use much (if any) in about 5k of normal driving.

The throttle body one was interesting - it's never been done as far as I know. I plan on watching commanded vs. actual throttle position when I get home and do my analysis. I appreciate the help!

 

[B-train]

Also, we have tried the cleared flood process and it does not help.

Finally, though, I have some additional information! The battery that was in it was bad, not horrible but it would drop to 11.5 under stress. So battery is replaced. We’ve also figured out a little bit more about how to use the scanner tool.
At idle: The MAF is right around five, which I think is where it should be. The fuel trims are very small and mostly positive, but I don’t know enough about that sort of thing to describe more. Haven’t been able to look at the fuel trims while driving because I am by myself most of the time.

There is an EBCM error, control, module communication bus off. That error could simply be me not knowing how to use the scanner but if not, how do I fix that?

There is a low-voltage on TFP switch #5 circuit. How do I fix that?

I noticed on the scanner there is a fuel shut off on deacceleration. What is that controlled by? Is that a relay that I could replace? To us, fuel shut off on deacceleration seems like exactly what the problem is!

Also, the auto ride suspension has been removed from the vehicle so every time it starts, we get a check, suspension error and of course, there are all sorts of notations on the scanner about the ESC. Is there a fuse or relay or something I could pull to convince the car this is not a problem?

We have not had time to test it under load. The other thing we have not done yet is replace the fuel sensor relay although I have it and will replace it before we test the vehicle. Thanks guys!

You can get the autoride simulators off ebay or Amazon. They're probably $100 for a set of 4. Plug them into the autoride connectors that used to go to the shocks and struts - no more light because the system is satisfied with the correct resistance it's looking for.

 

[solli5pack]

You can also wire in some resistors that fool the computer...you can get 5 for $10.

 

[Doubeleive]

Also, we have tried the cleared flood process and it does not help.

Finally, though, I have some additional information! The battery that was in it was bad, not horrible but it would drop to 11.5 under stress. So battery is replaced. We’ve also figured out a little bit more about how to use the scanner tool.
At idle: The MAF is right around five, which I think is where it should be. The fuel trims are very small and mostly positive, but I don’t know enough about that sort of thing to describe more. Haven’t been able to look at the fuel trims while driving because I am by myself most of the time.

There is an EBCM error, control, module communication bus off. That error could simply be me not knowing how to use the scanner but if not, how do I fix that?

There is a low-voltage on TFP switch #5 circuit. How do I fix that?

I noticed on the scanner there is a fuel shut off on deacceleration. What is that controlled by? Is that a relay that I could replace? To us, fuel shut off on deacceleration seems like exactly what the problem is!

Also, the auto ride suspension has been removed from the vehicle so every time it starts, we get a check, suspension error and of course, there are all sorts of notations on the scanner about the ESC. Is there a fuse or relay or something I could pull to convince the car this is not a problem?

We have not had time to test it under load. The other thing we have not done yet is replace the fuel sensor relay although I have it and will replace it before we test the vehicle. Thanks guys!

the only thing in that mess of stuff that would affect the engine is the transmission code, my guess is that is the possibly the issue.
suspension codes would "maybe" limit the max speed you could go, rare but can happen
ebcm would just throw a abs/brake light, brakes would still work.
fuel shut off on decel I believe is normal, I think in general terms that just means it is lowering requested fuel pressure, not actually cutting the fuel off period.

the transmission should be looked at.

 

[j91z28d1]

I got a buddy a few shops down that has one of the cop car ones, he was telling me his was doing something like this. turned out to be the tranny. when it was trying to stall he popped it in neutral and it stopped stalling or trying to stall. he bought a new converter, but didn't get around to putting it in.


just something to try.