2007 GMC Denali stalls after towing

[Cincikid]

" 2008, when I tow I constantly watch my torque app which has oil pressure and temperature. When cruising, pressure stays around 38 to 40 PSI, when idling it stays anywhere between 15 to 20. Oil temperature was running usually between 230 to 240."

15-20 psi hot idle is too low, this makes it highly likely that your problem is caused by the typical VVT/ low hot oil pressure problem. You can read the cause and solution details earlier in this thread: https://www.tahoeyukonforum.com/thr...stalls-after-towing.73312/page-7#post-1519861

Have you solved the issue by switching to a thinner oil?

 

[HD_LS]

Have you solved the issue by switching to a thinner oil?

You need a thicker oil. The hot oil pressure will be determined by the second number in the viscosity rating (the "50" in 5W-50, 10W-50, 20W-50) Choose one of those grades of oil. That will give you a good bit more hot oil pressure than running 5W-30 or 10W-30.

 

[DavesTractor]

You need a thicker oil. The hot oil pressure will be determined by the second number in the viscosity rating (the "50" in 5W-50, 10W-50, 20W-50) Choose one of those grades of oil. That will give you a good bit more hot oil pressure than running 5W-30 or 10W-30.

I agree. I just joined to share our experience in order to help others. My son has a 2008 Yukon Denali with the 6.2 at 180k miles. On long trips, he would sometimes get a stall when coming off the freeway. It would take 20-45 minutes before it would restart. Then it became more frequent, especially in the summer. Fuel pressure was always good. After checking cam and crank sensors and actually replacing them just in case, we still had the problem. When it would stall, we had proper fuel pressure as observed by a gauge, we had spark, and obviously, we had compression. That left timing as the only possible problem. We then monitored cam timing when it died and it was about 50 degrees off where it should be at an idle. 07 and 08s have up to 62* in cam timing. It was enough out of time that even a spritz of starting fluid into the throttle body would do nothing....and we had spark. As HD_LS has said more than once, this is a timing issue for many folks with good fuel pressure. Why? Low oil pressure. Long runs or pulling a trailer or running hard up hills will heat the engine oil more than normal. That thins it down. We were at 11psi hot oil. We changed to 10-40 and put in a bottle of Lucas and we now have not been able to observe anything under 22psi at hot idle. Cam phaser now works as it should, no more stall, etc.

We can then discuss why the low oil pressure and so forth. Briefly, the oil pickup tube o-ring is easy to check. It gets complicated from there, and a shop will often want to replace the engine. But depending on the situation, you might be able to change the oil and add Lucas and get quite a few more miles out of the engine. It's a bit of a bandaid, but it works. There is likely a little more clearance in the cam bearings, the oil pump, or the rods and mains than when new. A little thicker oil fills that gap and restores oil pressure, and will probably prolong the life of the engine.

I do not want to say that all the "hot stall with a hard restart issues" are oil pressure and cam phaser related. You still need to check codes, check fuel pressure, etc. But for sure put this in your bag of tricks as you diagnose.

 

[JEFFC]

Agree with all of what D said above. My problem was the vapor lock issue and wanted to point out that fuel pressure was normal during the no start condition. Don't assume it's not vapor lock just because fuel pressure is normal. Bleed fuel from rail with several key cycles and if it fires up, you found your problem.

 

[oldtimer]

I tried thicker oil (15W-50 M1).
Increased hot oil pressure from 16ish to 25ish PSI.
Thought that would fix problem, just like after insulating fuel rails, and replacing crank & cam sensors, and replacing fuel pump.
NOPE.
Long pull up Kingsbury grade,
air temp 77*,
tranny temp 217*,
coolant temp 259*,
oil temp 282*
oil pressure 40 psi.
Took foot of gas pedal, engine died.

Left key in on position, hooked up Tech2, no codes set.

Sat for 45 minutes while things cooled off,
tranny 187*,
coolant 198*,
oil 216*,
Restarted and ran like never any problem.

Ordered a Lithium jump start battery to power Tech2, so I can record Cam Retard angles when cranking engine.
Next step may be to replace oil pump (& O-ring), camshaft, and all VVT hardware . . . or maybe a 6.2L crate engine with warranty.

 

[JEFFC]

Oldtimer, have you tried bleeding fuel off from the fuel rail while the no start problem exist? Did you also wrap the fuel line running to the fuel rail and over the top of trans?

 

[DavesTractor]

Jeffc, thanks for that response. Good to know that fuel rail pressure does not in any way rule out vapor issues. We bleed fuel several times and always had pure fuel, no air. What got us going on the fix for our problem was the fact that we had spark and fuel and it cranked but would not start. That pointed to timing. I've read of several cases that were for sure vapor lock, so that can absolutely be the issue. Therein lies the problem, there are several things that can cause very similar symptoms. Having a method to diagnose them in an orderly fashion would be nice. We kind of poked around until we found the timing issue.

Oldtimer, good idea to record cam timing to see where it is at when it stalls.

 

[Fless]

I tried thicker oil (15W-50 M1).
Increased hot oil pressure from 16ish to 25ish PSI.
Thought that would fix problem, just like after insulating fuel rails, and replacing crank & cam sensors, and replacing fuel pump.
NOPE.
Long pull up Kingsbury grade,
air temp 77*,
tranny temp 217*,
coolant temp 259*,
oil temp 282*
oil pressure 40 psi.
Took foot of gas pedal, engine died.

Left key in on position, hooked up Tech2, no codes set.

Sat for 45 minutes while things cooled off,
tranny 187*,
coolant 198*,
oil 216*,
Restarted and ran like never any problem.

Ordered a Lithium jump start battery to power Tech2, so I can record Cam Retard angles when cranking engine.
Next step may be to replace oil pump (& O-ring), camshaft, and all VVT hardware . . . or maybe a 6.2L crate engine with warranty.

Not sure it's germane to the current issue, but that coolant temp seems awful high.

 

[oldtimer]

Oldtimer, have you tried bleeding fuel off from the fuel rail while the no start problem exist? Did you also wrap the fuel line running to the fuel rail and over the top of trans?

Jeffc,
Yes & No.
When it died in Beaver Utah I vented the Schrader valve on insulated fuel rail, it sprayed liquid gas every where, so no vapor lock. Therefore I did not try to insulate fuel lines behind engine and transmission.
Also, since it died in front of Napa store, I tried ether into intake with no start. Since I had ether and time to wait, I sprayed ether on ECU and other sensors to see if chilling them would allow restart. That's when I bit the bullett, and had dealer install new fuel pump. Old pump was borderline bad, but still had hot stall issue.

Not sure it's germane to the current issue, but that coolant temp seems awful high.

Fless,
I thought it might be high, but dash gauge never shows much above 240ish, has redline at 260, and cooling system has never expressed any coolant.
259* is what OBDwiz displays on laptop computer, along with above oil and tranny temps.
I am more concerned with 282* for oil temp, but that may not be excessive.

Would appreciate comments on oil temp, and I may add an oil cooler.

 

[avalonandl]

Add oil cooler is my suggestion

 

[JEFFC]

Jeffc,
Yes & No.
When it died in Beaver Utah I vented the Schrader valve on insulated fuel rail, it sprayed liquid gas every where, so no vapor lock. Therefore I did not try to insulate fuel lines behind engine and transmission.
Also, since it died in front of Napa store, I tried ether into intake with no start. Since I had ether and time to wait, I sprayed ether on ECU and other sensors to see if chilling them would allow restart. That's when I bit the bullett, and had dealer install new fuel pump. Old pump was borderline bad, but still had hot stall issue.


Fless,
I thought it might be high, but dash gauge never shows much above 240ish, has redline at 260, and cooling system has never expressed any coolant.
259* is what OBDwiz displays on laptop computer, along with above oil and tranny temps.
I am more concerned with 282* for oil temp, but that may not be excessive.

Would appreciate comments on oil temp, and I may add an oil cooler.

Did it fire at all with the ether?

 

[kbuskill]

Jeffc,
Yes & No.
When it died in Beaver Utah I vented the Schrader valve on insulated fuel rail, it sprayed liquid gas every where, so no vapor lock. Therefore I did not try to insulate fuel lines behind engine and transmission.
Also, since it died in front of Napa store, I tried ether into intake with no start. Since I had ether and time to wait, I sprayed ether on ECU and other sensors to see if chilling them would allow restart. That's when I bit the bullett, and had dealer install new fuel pump. Old pump was borderline bad, but still had hot stall issue.


Fless,
I thought it might be high, but dash gauge never shows much above 240ish, has redline at 260, and cooling system has never expressed any coolant.
259* is what OBDwiz displays on laptop computer, along with above oil and tranny temps.
I am more concerned with 282* for oil temp, but that may not be excessive.

Would appreciate comments on oil temp, and I may add an oil cooler.

I have an aftermarket oil cooler, not the factory oil cooler, and my oil temperature runs consistently at around 210°- 215°.

To give a little more context, this is just with normal driving around town or on the interstate, not towing or anything. This is in the Florida heat, however I do have a larger oil quantity than stock due to the dual remote mount oil filter setup and external oil cooler. My oil system holds 9 quarts which is 1.5 times the factory capacity of 6 quarts.

 

[oldtimer]

Did it fire at all with the ether?

No hint of wanting to start, with ether.
That's why I am leaning towards camshaft stuck at full retard.

 

[ryanmichael]

Hi all - First time posting here. Thanks for all your efforts to this point.

I have a 2007 Yukon XL Denali with the 6.2. I bought it to tow a 6000 pound (when loaded) travel trailer for a cross-country trip coming up soon. When not towing I haven't had any problems. I recently had the camshaft position sensor replaced due to a CEL that came on when towing. The CEL caused loss of power and a few other crazy things.

After replacing the sensor and towing again, the truck initially seemed good. I live in a very hilly part of Virginia, and when driving, the engine temp was around 210 except for longer sustained inclines, where the temp would get to around 220 for a short time. The trans temp was usually around 200, but would get to 210 on the climbs. Both engine and trans temp would cool down shortly after cresting hills. Oil pressure was running a consistent 40psi while driving.

The only problem was when I came to a stop. The oil pressure dropped to around 20 or just below, and the idle become quite rough and seemed like the engine was going to stall, but luckily never stalled. Then, when trying to accelerate out of the stop, the accelerator was not responsive, and the engine rpms would not increase. After pumping/flooring the accelerator for around five seconds the engine seemed to finally get some fuel and pickup again. After the rpms went up the oil pressure was back to 40 and cruising along is just fine. This stopping problem happened a few times. At some of the next stops I was able to feather the accelerator while coming to a stop to avoid the rpm drop and following issues (oil pressure drop/idle/accelerator problems). There was never a CEL, but there was a random stabiltrack / traction control service light that came on when going up a steep hill, but that went away after a couple mins.

These issues all happened when the engine oil (not sure what type, as I just bought the truck) was on the low end of the "okay" range on the dipstick, but today I replaced engine oil to a 10w-40 synthetic. Also recently replaced the battery, had all new trans fluid and t-case/diff fluids replaced, and new spark plugs and coils/wires. I plan on towing again with the truck asap to see if the new oil helps.

I want to have the fuel pressure looked at and possibly diagnose a vapor lock issue, but this is difficult due to the towing exclusive problems. I want to add a larger transmission cooler and maybe heat-protect the fuel lines. Some people's success with trans coolers and others' with protecting fuel lines makes me want to do both and hope for the best.

I only have three weeks til my trip and don't want to stall out on an off-ramp in the middle of Arizona when it'll inevitably be 120 degrees this July.

It seems like my problems are similar to many of you, but I'm wondering if my issues lead any of you to think my issue is more or less related to any of the specific fixes/issues you've mentioned.

Any thoughts or suggestions you might have would be greatly appreciated!!

 

[HD_LS]

Hi all - First time posting here. Thanks for all your efforts to this point.

I have a 2007 Yukon XL Denali with the 6.2. I bought it to tow a 6000 pound (when loaded) travel trailer for a cross-country trip coming up soon. When not towing I haven't had any problems. I recently had the camshaft position sensor replaced due to a CEL that came on when towing. The CEL caused loss of power and a few other crazy things.

After replacing the sensor and towing again, the truck initially seemed good. I live in a very hilly part of Virginia, and when driving, the engine temp was around 210 except for longer sustained inclines, where the temp would get to around 220 for a short time. The trans temp was usually around 200, but would get to 210 on the climbs. Both engine and trans temp would cool down shortly after cresting hills. Oil pressure was running a consistent 40psi while driving.

The only problem was when I came to a stop. The oil pressure dropped to around 20 or just below, and the idle become quite rough and seemed like the engine was going to stall, but luckily never stalled. Then, when trying to accelerate out of the stop, the accelerator was not responsive, and the engine rpms would not increase. After pumping/flooring the accelerator for around five seconds the engine seemed to finally get some fuel and pickup again. After the rpms went up the oil pressure was back to 40 and cruising along is just fine. This stopping problem happened a few times. At some of the next stops I was able to feather the accelerator while coming to a stop to avoid the rpm drop and following issues (oil pressure drop/idle/accelerator problems). There was never a CEL, but there was a random stabiltrack / traction control service light that came on when going up a steep hill.

These issues all happened when the engine oil (not sure what type, as I just bought the truck) was on the low end of the "okay" range on the dipstick, but today I replaced engine oil to a 10w-40 synthetic. Also recently replaced the battery, had all new trans fluid and t-case/diff fluids replaced, and new spark plugs and coils/wires. I plan on towing again with the truck asap to see if the new oil helps.

I want to have the fuel pressure looked at and possibly diagnose a vapor lock issue, but this is difficult due to the towing exclusive problems. I want to add a larger transmission cooler and maybe heat-protect the fuel lines. Some people's success with trans coolers and others' with protecting fuel lines makes me want to do both and hope for the best.

I only have three weeks til my trip and don't want to stall out on an off-ramp in the middle of Arizona when it'll inevitably be 120 degrees this July.

It seems like my problems are similar to many of you, but I'm wondering if my issues lead any of you to think my issue is more or less related to any of the specific fixes/issues you've mentioned.

Any thoughts or suggestions you might have would be greatly appreciated!!

120 Degrees in Arizona? I would get serious and focus on the high percentage likelyhood fixes. 1) Take it to a local tuning shop that tunes LS engines (Corvette, Camaro, etc), and have them program your ECM to disable the VVT. As others on the Forum have done. You can have them program the fans to come on at a lower temperature, while they are at it. 2) Get serious about the oil: 5W-50, 10W-50, 20W-50. Not just a half way step to 10W-40. https://www.amsoil.com/p/signature-series-5w-50-synthetic-motor-oil-amr/

 

[Geotrash]

There was never a CEL, but there was a random stabiltrack / traction control service light that came on when going up a steep hill.

This part has my attention. Did you read the stored codes? The stabilitrak/TC warning will come on when the ECM detects a problem with any one of several engine management systems, including the fuel system. I used to get this message on my 2007 and the OBD2 code was high fuel pressure, ultimately indicating that the in-tank pressure regulator was failing. A new OEM fuel pump assembly solved the problem for me.

 

[ryanmichael]

Thanks for the replies and direction. I'm going to test drive while pulling the trailer first to see if 10-40 oil helps. @HD_LS , do you think there are risks at all of going to the 10w-50? Engine tuning sounds good too. I'll read those threads you mentioned.

I have a tru cool 40k Trans cooler on order too. Even if that doesn't solve the problem hopefully it'll reduce the temperature/wear and tear while on my long trip across the desert.

I'm going to check the codes too to see if anything shows based on the intermittent service stabiltrack / traction control lights.

Thanks!

 

[avalonandl]

I would stick to 10-40 oil. 20 psi hot at idle is ok.

 

[ryanmichael]

After putting in 10w-40 oil I towed my TT over the blue ridge and the truck did quite a bit better. The hot low idle was smoother and oil pressure was 25 rather than below 20. While cruising the oil pressure was around 45-48, while before it was 17-18 at idle and 40 while cruising.

While towing for about 2 hours, I came to a handful of stops, and the idle only stuttered once, and I experienced the unresponsive accelerator only once. That's much better than before I changed the oil, when the low OP and rough idle and no accelerator response happened at every stop. Going over the pass the trans temp got to 220 going up the steep pass, and the engine temp got to about 220 as well.

Driving back home I had more problems. Before hitting the pass the trans temp got up to 220 and engine temp was similar, I got a stabilitrak and traction control light and warning, the engine idle at a stop was really rough, low speed hard shifts in the trans, and also low power even when cruising down the road. I ran my new OBDII code reader and it showed the notorious p0011 (cam position issue), a p0174 (system too lean), B1516 (body control), C0561 (anti-lock brake). After limping along for maybe 15-20 min, the trans temp slowly increased to 230, and I hadn't even hit the pass yet. Then the stabilitrak and traction control sensor light and warnings just went away.

Curiously, right after the lights resolved and turned off, the trans temp cooled down to normal flat-land towing temp (200) within just a few moments. This suggests that there's a connection in trans temp with the codes I got, but I don't understand the connection. The engine power returned and I braved the steep climb up the blue ridge. It ran at about 4000 rpm in 2nd going about 40 mph up the steep pass. Trans temp got to 230 and engine around 225. Made it the rest of the way home just fine after that.

That night I installed my tru cool 40k cooler then took it out the next day back and forth over the same pass. The max trans temp over the pass going both ways was 180, with the engine temp just over 215. Towing on the flat land the trans temp was around 160. After driving for 3-4 hours with many stops, starts, on ramps and off ramps, the truck never towed better. Oil pressure stayed above 25 at idle, never a stutter in the engine idle, no lights, no loss of power, and everything just worked great. I didn't clear the codes bc I wanted to be sure my mechanic could take a look and see if something else shows up. Now, the trans temp when not towing won't go over 135, even when it's 85 degrees out. Before the cooler it ran around 160-170 when not towing.

Now my truck is in the shop again to see if there's anything else the codes suggest might need attention. I'll report when I get my truck back. I'm thinking maybe the p0011 code might need to have more cam position work done, including maybe the oil pickup o-ring. Looks like @HD_LS was right about vvt issues. We'll see what the shop says. No tuners close by.

Thanks again for all your help. So, right now I'm in the higher viscosity oil camp, and the trans cooler camp. Haven't yet checked the fuel pressure issue, but with the trans cooler now that seems unnecessary. Luckily, my rig never completely stalled at idle, and hopefully we can prevent it!

 

[emamon]

I had this exact same happen on a different vehicle (still GM though) and it was the crankshaft position sensor. It would get hot, screw up, and tell the computer the crank wasnt spinning so it shut down the fuel injectors. After it cooled down, it fired up and ran fine.

At least thats where I would start, I remember it being about ten bucks and one bolt

This has happened to me 3 times in the past 5 weeks. Glad I found this thread. I have the '08 L92 6.2L. Each time would be towing in about 81-83F temp and come to idle at a stop. First time I was on the interstate... in rush hour... in a construction zone (and stop and go for a mile) against the left side temporary wall. Had to be towed out on flatbed with trailer towed behind it. Happened twice yesterday and would restart after 25-40 minutes. I bought a set of tools to keep in the truck (now that it has 139K and wants to be ******), will go replace the fuel pump relay for the hell of it... but my $$$ is on the crank position sensor. I want to know how an at home mechanic did the CPS relearn procedure after replacing it???? No injector pulse sounds exactly like what was going on....