2007 GMC Yukon XL Denali, 6.2L Stalls When Warm

[anonom2]

2007 GMC Yukon XL Denali 6.2L, stalls and won't restart when warm.

 

Conditions & Symptoms

1. Car is warm (Aprox. 15 minutes of driving)

2. Typically won't restart without struggle until cooled down (Anywhere from 15-30 minutes)

3. Trans temps are anywhere from 136-150 Degrees when it occurs. 

4. It will only stall when coming to a stop, & can be kept running if it is revved.

 

I can replicate the issue after I get it restarted by moving the car in reverse 6 feet, then move it in drive 6 feet. Once I come to a stop the engine starts to run awful and bogs. Occasionally it will die when bogging, and other times it will stay running. However, if I cycle the traction control off/on it will die. If I rev the engine while the bogging is present, it will settle and run great & cycling the traction control has no affect. If I shut the engine off, it will turn on without issue. If I let it die, it won't restart.

 

If it bogs and dies it is a struggle to get it restarted while warm. It will typically only restart in neutral, I place it in neutral, turn traction control off, crank it, while it is cranking I continually press the traction control button, repeat the steps and it will eventually start. It takes anywhere from 30 seconds to 5 minutes of doing this. Once it starts it runs fantastic until I put it in reverse/drive like I stated previously.

 

EDIT: I also think its worthy to note that when trying to remote start it won't even attempt, I just get a slight click. The dome lights also don't work when the door is opened. And at one point the key chime wasn't working.

 

A lot of parts have already been replaced in attempt to fix this issue. Looking for some input on what could be causing this.

 

 

 

Edited April 3, 2020 by JunkyardJameson

[riverbanks]

Sounds like it's vaporlocking,search this forum,a few weeks back,close to same issue

[silveradosid]

how many miles on it what have you replaced , have you cleaned the throttle body

[Doug_Scott]

We're the parts replaced because they were properly tested and failed, or you used the highly ineffective "by guess by golly" method. 

The problem you now have is one of those parts you replaced may have been defective(that's why new parts come with a warranty). 

As already asked, you should post a list of the parts replaced.  If you don't touch the traction control button, does the truck behave the same way?  How did you decide to try pushing/holding the button while cranking? 

[anonom2]

7 hours ago, riverbanks said:

Sounds like it's vaporlocking,search this forum,a few weeks back,close to same issue

Iv'e read about this "Vaporlocking" issue but find it hard to believe. The issue started suddenly, along with the fact sufficient fuel pressure is present... & no vapor is being released from the schrader valve when opened. I also tested this theory by placing ice and water on the fuel rails, the rails were ice cold to the touch and the car still wouldn't start.

 

Or maybe I am completely misunderstanding vaporlock.

 

 

6 hours ago, silveradosid said:

how many miles on it what have you replaced , have you cleaned the throttle body

Aprox. 180k miles

 

Parts Replaced:

1. Throttle Body (Guess)

2. VVT Components (Guess)

3. Crankshaft Sensor (Inconsistent readings)

4. ECM (Guess)

5. Fuel pump (Shop diagnosis)

6. Ignition Switch (Guess)

7. Alternator (Alternator tested bad by shop)

8. Battery (Battery tested bad)

9. Battery Cables (Shop recommendation) 

10. Various Harness Connectors (Inconsistent readings)

 

1 hour ago, Doug_Scott said:

We're the parts replaced because they were properly tested and failed, or you used the highly ineffective "by guess by golly" method. 

The problem you now have is one of those parts you replaced may have been defective(that's why new parts come with a warranty). 

As already asked, you should post a list of the parts replaced.  If you don't touch the traction control button, does the truck behave the same way?  How did you decide to try pushing/holding the button while cranking? 

See above for replaced parts. Some parts were just replaced, others tested and failed. The car has been to 3 shops including the dealer, every single one had there own diagnosis... parts were replaced, and the issue still persists. 

 

If I don't touch the traction control button the car won't start until the engine cools down, and doesn't even sound like it wants to start. When I fiddle with the traction control button it will start to spudder slightly. I was just messing with anything I possibly could when it wouldn't start... lucky guess?

[508gm1]

Mass air flow sensor? I don't know how to function test it, maybe someone here does. I'm sure you are tired of throwing parts at it. In your video, the idle rpm's are erratic. is this actually happening, or is this you touching the throttle? Noticed your check engine light is on; do you know what it is?

 

I want to throw a dart in the dark and say a crappy ground connection somewhere, but you indicated the main battery cables were already replaced.

[anonom2]

1 hour ago, 508gm1 said:

Mass air flow sensor? I don't know how to function test it, maybe someone here does. I'm sure you are tired of throwing parts at it. In your video, the idle rpm's are erratic. is this actually happening, or is this you touching the throttle? Noticed your check engine light is on; do you know what it is?

 

I want to throw a dart in the dark and say a crappy ground connection somewhere, but you indicated the main battery cables were already replaced.

MAF was replaced with the throttle body, forgot to add that to the list. I'm probably missing some more stuff too. RPMs are erratic I wasn't touching the throttle during the videos. Check engine light is on, when I replaced the ECM it threw a code for Crank Position Sensor Calibration (Or something along those lines) and the same issues persisted. I'm assuming the new ECM needs to relearn the crank position?, it just hasn't had a chance to.

[508gm1]

If you start the truck when it is stone cold, how long will it idle until the rpm's start to go erratic? Does the truck have erratic rpm's when you first start it? I don't think my limited knowledge is going to help, but maybe if we banter back and forth enough, someone else will have a eureka moment.

 

I wouldn't think the ecm would "relearn" the crank position. I don't think it has any outside influences; it is what it is. Can someone confirm I am need feeding Mr. Jameson a line?

[anonom2]

22 minutes ago, 508gm1 said:

If you start the truck when it is stone cold, how long will it idle until the rpm's start to go erratic? Does the truck have erratic rpm's when you first start it? I don't think my limited knowledge is going to help, but maybe if we banter back and forth enough, someone else will have a eureka moment.

 

I wouldn't think the ecm would "relearn" the crank position. I don't think it has any outside influences; it is what it is. Can someone confirm I am need feeding Mr. Jameson a line?

It won't occur at if it has just been idling, only when it has been driven and stopped to an idle. The truck runs great on cold start, and even when it warm occasionally. 

 

Yeah, I'm not completely sure... it was just an assumption based on what the code said. 

[508gm1]

Would you be able to start the truck from cold and let it idle for 20 or 30 minutes to see if the fluctuating idol condition happens? Monitor what the rpm's are doing during warm up. I assume you are using premium fuel? If it behaves fine in the driveway, I wonder if there could be a transmission issue.

Edited April 3, 2020 by 508gm1

[508gm1]

Can you humor me and idle it for 20-30 minutes in the driveway and watch for fluctuating rpm's like shown in your video.

[riverbanks]

Good test on the vapor lock,that's out of the way,did you have a cel with 1st pcm?and was the code checked with a scanner that can read all codes?

Edited April 4, 2020 by riverbanks
Another question

[anonom2]

45 minutes ago, 508gm1 said:

Can you humor me and idle it for 20-30 minutes in the driveway and watch for fluctuating rpm's like shown in your video.

Absolutely willing to try anything at this point. I'll do it as soon as I have time, and get back.

 

18 minutes ago, riverbanks said:

Good test on the vapor lock,that's out of the way,did you have a cel with 1st pcm?and was the code checked with a scanner that can read all codes?

No CEL with the first PCM. The code was checked with a cheap OBD2 scanner. However, when it was at the shops they used more advanced scanners and reported no codes. That was pre-PCM swap though.

Edited April 4, 2020 by JunkyardJameson

[riverbanks]

Gotya,go to gmupfitter.com,look up the harness for your truck,and test injector wiring when it's misbehaving,I'm thinking that route, cause if it was spark dropping out,you would get black smoke or raw fuel smell on restart,and the remote start won't work with a cel,so if you got a crankshaft relearn procedure done that would work again

[Doug_Scott]

If you are just replacing parts you run the risk of introducing new issues.  I know you can't return these parts, but I would put the old part back on if the replacement part made no difference.  If you have the original ECM, put it back on and get rid of CEL.  

Have you checked the fuel pressure while cranking?

Have you tried flooring the throttle, then turning the key to start?  Doing this engages the clear flood mode and will not inject fuel until the engine starts. 

Try removing a couple of the easy to get at spark plugs when the issue is present, and inspect the engine side of the plugs for presence of raw fuel or oil. 

If there is no CEL with original ECM, you are pretty safe in moving away from engine electronics.  Normally when no codes are present and the engine is acting up, the mechanic should start at the three traditional systems, fuel, compression and spark.  By traditional I mean the mechanical side of it. Having fuel in the rail is only half the fuel test.  It must be getting into the cylinder as well. You should be able to take a long screwdriver and place the top against a fuel injector, and put your ear against the handle end and crank the engine over.  You should hear the injector opening and closing. Check them all, and see if they all sound the same. 

[tlaw91]

Did you take this to the dealership, have them give you a diagnosis, then replace that part yourself and never go back or did you have them do the work it didn’t fix it then not go back?


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