07 yukon XL denali dies at idle when hot after 15 min

[Joeroket]

I have an 07 yukon xl1500 denali that runs good until about 10 minutes or so of driving after it is warmed up. It runs as long as I keep the throttle cracked a little but at idle it will die and wont start for around 20 min. Has been to a local shop that was stumped and the dealer who said they couldnt reproduce it and told me my battery and negative cable was bad and that was probably causing the issue. The local shop did tell me that he watched all sensor voltages slightly increase for no apparent reason and that has him thinking its an electrical issue. The dealer told me they were seeing voltages randomly dip, thus their diagnosis that the neg cable and battery were the culprit

 

 

I have changed the fuel pump, crank sensor, the three cam position sensor components, throttle body, alt, battery (it was actually bad) connector for the crank and cam sensors, and both battery cables. I have also cleaned the ground points and connectors for the both battery cables. When testing the grounds I have never seen more than .1 ohms from any point to any other point. The positive side shows full continuity from the starter post to the fuse block.

 

When it warms to running temp it runs rough. Tonight it died so I waited it out and started it up after about 20 minutes. While it was in the driveway I popped the hood and grabbed my meter, it was running pretty rough, to verify voltages and ground. Everything seemed fine but I noticed that after the hood was open for about 5 minutes it started idling better. I shut the hood and gradually the idle started to get rough so I opened the hood again and the idling smoothed out. Closed it once again and the roughness returns. It certainly seems like a heat issue in the engine bay. Also I have never been able to reproduce the dying issue in my driveway no matter what I do. It only does it when on the road.

 

The only thing I can think of now is that the harness has an issue somewhere and something is increasing in resistance under the high temps of a closed hood.

 

Any ideas?

[riverbanks]

What about cat converters? when it dies,I'd be ready to unscrew front 02's,see if it starts

[Joeroket]

I can try that. The shop did do a back pressure test and he said it was ok. The local shop was able to troubleshoot while the hot no start condition existed.

[riverbanks]

Hmm?is the truck vaporlocking?what about pouring water on fuel rails when it dies? just trying to think outside the box,if scanner couldn't catch it,or, maybe disconnect MAF when dead,it could go flaky,and underreport

[riverbanks]

Still thinking,on gmupfitter site,you will find all ground locations,worth a look,or,do the old wire harness wiggle test,I use a dowel, just move all wires a little bit, you never know if in the past, somebody probed a wire and never sealed it

[Joeroket]

1 hour ago, riverbanks said:

Hmm?is the truck vaporlocking?what about pouring water on fuel rails when it dies? just trying to think outside the box,if scanner couldn't catch it,or, maybe disconnect MAF when dead,it could go flaky,and underreport

It doesn't appear to be vapor locking. There is 60 Lbs of pressure and when I crack the Schrader valve when it is a no start condition it has a nice flow of fuel.

[Joeroket]

1 hour ago, riverbanks said:

Still thinking,on gmupfitter site,you will find all ground locations,worth a look,or,do the old wire harness wiggle test,I use a dowel, just move all wires a little bit, you never know if in the past, somebody probed a wire and never sealed it

Thanks for that. I will take a look and check all the ground locations. I have tried the wiggle test on the main portion of the harness that feeds the knock, crank, and cam sensors. I even pulled that section of the harness out for a visual inspection and found nothing of note.

[riverbanks]

What is not there at no start?got to isolate,have spare spark plug,pop in wire when dead,try it,or fuel,ear to screwdriver on a injector,audible click?or if you think lean start, unplug cts,richen it up a bit,or just spray carb clean in throttle body

[swathdiver]

11 hours ago, Joeroket said:

I have an 07 yukon xl1500 denali that runs good until about 10 minutes or so of driving after it is warmed up. It runs as long as I keep the throttle cracked a little but at idle it will die and wont start for around 20 min. Has been to a local shop that was stumped and the dealer who said they couldnt reproduce it and told me my battery and negative cable was bad and that was probably causing the issue. The local shop did tell me that he watched all sensor voltages slightly increase for no apparent reason and that has him thinking its an electrical issue. The dealer told me they were seeing voltages randomly dip, thus their diagnosis that the neg cable and battery were the culprit

 

 

I have changed the fuel pump, crank sensor, the three cam position sensor components, throttle body, alt, battery (it was actually bad) connector for the crank and cam sensors, and both battery cables. I have also cleaned the ground points and connectors for the both battery cables. When testing the grounds I have never seen more than .1 ohms from any point to any other point. The positive side shows full continuity from the starter post to the fuse block.

 

When it warms to running temp it runs rough. Tonight it died so I waited it out and started it up after about 20 minutes. While it was in the driveway I popped the hood and grabbed my meter, it was running pretty rough, to verify voltages and ground. Everything seemed fine but I noticed that after the hood was open for about 5 minutes it started idling better. I shut the hood and gradually the idle started to get rough so I opened the hood again and the idling smoothed out. Closed it once again and the roughness returns. It certainly seems like a heat issue in the engine bay. Also I have never been able to reproduce the dying issue in my driveway no matter what I do. It only does it when on the road.

 

The only thing I can think of now is that the harness has an issue somewhere and something is increasing in resistance under the high temps of a closed hood.

 

Any ideas?

Your fuel is getting too hot.  For some reason on those first year Denalis, some of them get fuel their fuel lines too hot and they shut down as you describe.  Insulate the fuel line coming up the back of the motor and fuel rail.  How old is the battery?  Has it been PROPERLY tested for load and internal shorts?  

[Joeroket]

10 minutes ago, swathdiver said:

Your fuel is getting too hot.  For some reason on those first year Denalis, some of them get fuel their fuel lines too hot and they shut down as you describe.  Insulate the fuel line coming up the back of the motor and fuel rail.  How old is the battery?  Has it been PROPERLY tested for load and internal shorts?  

Battery and Alt are brand new, old Alt had .4V of ripple current and old battery did test bad, but the problem started a while back and has been a pain in the arse since August. I do have some heat wrap laying around that I can throw on the rail and see if that helps.

[Joeroket]

38 minutes ago, riverbanks said:

What is not there at no start?got to isolate,have spare spark plug,pop in wire when dead,try it,or fuel,ear to screwdriver on a injector,audible click?or if you think lean start, unplug cts,richen it up a bit,or just spray carb clean in throttle body

Spark, fuel, and air are all present at time of no start. Injectors have pulse during this time. I will take a can of carb clean with me next drive.

[swathdiver]

https://www.tahoeyukonforum.com/threads/engine-stalling-in-the-heat.112348/#post-1348763

 

https://www.tahoeyukonforum.com/threads/2007-yukon-denali-stalling.111715/page-8#post-1408646

 

https://www.tahoeyukonforum.com/threads/2007-denali-rough-idle-and-stall-after-running-long.101129/

 

https://www.tahoeyukonforum.com/threads/2007-6-2-dies-after-highway-drive.109437/#post-1306016

 

https://www.tahoeyukonforum.com/threads/2007-gmc-denali-stalls-after-towing.73312/

[Joeroket]

Interesting reading. Thanks for posting those. I guess the heat warp on the fuel rails will be my first thing now.

[DohDoh]

On 2/25/2020 at 11:28 AM, Joeroket said:

Interesting reading. Thanks for posting those. I guess the heat warp on the fuel rails will be my first thing now.

Did wrapping your fuel rails solve the issue? I have a 07 6.2 doing the same thing. 

[AEHEART]

Joeroket did you ever figure it out?!?!!? Experiencing the same issues with my 2007 yukon denali now.