2007 Yukon Denali stalling

[vettes980]

@Bruce Mace How's your Yukon? Any recurrence of the issue since replacing the fuel pump back in early May? I am having the same issue and can't tell what my next move should be. Any information would be much appreciated.

Same issue. Limped home 14 hours today. As long as I was moving all was fine. Stopping for gas or anything else was a crap shoot if it stayed running. Had lean bank 1/2 P0171 P0174 that I thought was caused by cracked intake manifold vacuum line and replaced yesterday. Made idle better and gave a false assurance for my trip home. One stall required a floored pedal and continuous crank to get it to restart. Other time started up after it stalled pulling into parking spot and it sat for a few hours. After all that, I just kept the revs up when I had to stop or slow. Died again as I coated into the driveway. Anyone?


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[Doubeleive]

Same issue. Limped home 14 hours today. As long as I was moving all was fine. Stopping for gas or anything else was a crap shoot if it stayed running. Had lean bank 1/2 P0171 P0174 that I thought was caused by cracked intake manifold vacuum line and replaced yesterday. Made idle better and gave a false assurance for my trip home. One stall required a floored pedal and continuous crank to get it to restart. Other time started up after it stalled pulling into parking spot and it sat for a few hours. After all that, I just kept the revs up when I had to stop or slow. Died again as I coated into the driveway. Anyone?


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Get a cheap fuel pressure gauge and check your fuel pressure, should be around 60-65psi with just the key on and then should drop to 48-50psi with the engine running.

 

[vettes980]

Get a cheap fuel pressure gauge and check your fuel pressure, should be around 60-65psi with just the key on and then should drop to 48-50psi with the engine running.

Just got one and recreated the stalling. Fuel pressure is the same when working fine and in a stall situation.

No codes to speak of.


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[vettes980]

I’m leaning towards the TAC motor in the throttle body. As I coast into the driveway it will stall, won’t restart until I hold the pedal to the floor and crank for an extended period. Once it restarts it’s like nothing is wrong. Will idle just fine, shut down and restart without issue.


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[Doubeleive]

Just got one and recreated the stalling. Fuel pressure is the same when working fine and in a stall situation.

No codes to speak of.


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HMM, ok could be different things then, you really need a scanner to troubleshoot the problem, but could be maf (mass air flow sensor), throttle body, map sensor, etc you need something that can read live data, not sure what you want to spend on it but a clone tech2 runs 300-350 on ebay, a cheap bluetooth elm device could read live data but wont do what a tech2 can. without at least getting some live data it's kind of a guessing game. @swathdiver have any ideas?

 

[swathdiver]

HMM, ok could be different things then, you really need a scanner to troubleshoot the problem, but could be maf (mass air flow sensor), throttle body, map sensor, etc you need something that can read live data, not sure what you want to spend on it but a clone tech2 runs 300-350 on ebay, a cheap bluetooth elm device could read live data but wont do what a tech2 can. without at least getting some live data it's kind of a guessing game. @swathdiver have any ideas?

I'm with you, we're just guessing and throwing parts at it without the proper tools for diagnosis.

Whatever this is, seems to be pretty common though, 3 or 4 guys with it in the same thread.

 

[kbuskill]

I’m leaning towards the TAC motor in the throttle body. As I coast into the driveway it will stall, won’t restart until I hold the pedal to the floor and crank for an extended period. Once it restarts it’s like nothing is wrong. Will idle just fine, shut down and restart without issue.


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The way you describe holding the pedal to the floor and cranking sounds almost like the engine is flooded.

On these trucks holding the pedal to the floor and cranking causes the fuel injectors to be disabled so that you can clear the engine if its flooded.

I wonder if the evaporative emissions system is acting up and allowing fuel vapors to flood the engine via the purge valve???

 

[thompsoj22]

ok thx I will look into it so far the new fuel pump seems to have solved the problem crossing my fingers

im pretty sure your vehicle has no fuel return/pulse damper, the pressure is regulated by a pump module that varies pump speed as needed. It is soooo necessary to have the scanner running while your driving to isolate the problem to the correct system/component. If the new pump made a difference and it was the only component replaced in that repair i would "guess" fuel related. fuel pressure to ECM, ECM to module or module to pump. i love guessing with opm, but it is embarrassing when it turns out to be somthing as simple as a corroded/loose connector?

 

[vettes980]

I do have a live data scanner. Autel Maxicom 808 something. I did confirm that all the usual culprits were in spec while driving. I could recreate the stalling consistently and the procedure to get it restarted. Once restarted, it would restart without issue while parked over and over. I installed an AC delco throttle body this morning and made it to work without any stalling where it would usually stall once I pull into park. Not going to claim victory yet as one drive w/o issue is just that, one data point.

I’ve been guided through this by my ASE friend and of course from advice on here. Will update after a few more cycles.


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[vettes980]

The way you describe holding the pedal to the floor and cranking sounds almost like the engine is flooded.

That’s exactly my thought and with all that has gone on with it, I suspect the TAC motor controlling the throttle body is out of sync or failing causing the butterfly to not work under idle. I had codes for the the throttle body when I bought it 1 year and 12k miles ago. I just cleaned it and the codes never came back. It’s always been in the back of my mind that I just prolonged its death. Cheap is expensive.