Dying on idle.

[2007 Denali XL]

Here is the hot soak fuel pressure test. On my test drive the pressure gauge needle was very steady on the drive out, but after stopping for 20 mins, on the return journey the needle flickered a lot like you see here in the hot soak.

 

[Doubeleive]

what happens with the fuel pressure when/as-it dies?

 

[OR VietVet]

what happens with the fuel pressure when/as-it dies?

Exactly. That is the key. If it stays fine, then move on to a different diagnosis.

 

[2007 Denali XL]

what happens with the fuel pressure when/as-it dies?

the dying symptom is not consistent, it kinda only comes along after heavy hot drive. Should be able to recreate that over the next few days

 

[dubyagee01]

If I remember correctly theres a check calve in the fuel system that keeps the lines full. If its bad the lines drain out and it gets hard to start or the fuel lines may have been moved with the trans work and they are near a hot spot and the fuel is boiling in the line.

 

[PNWYukon]

The fuel pressure should be steady and not bounce around at all. You should really find/buy/rent a good scan tool and monitor the live data/mode 6 data like your fuel trims, misfires, injector pressures, etc., to really see what is happening. Otherwise you may just keep chasing in circles.

 

[2007 Denali XL]

If I remember correctly theres a check calve in the fuel system that keeps the lines full. If its bad the lines drain out and it gets hard to start or the fuel lines may have been moved with the trans work and they are near a hot spot and the fuel is boiling in the line.

do you know where that valve is?

 

[dubyagee01]

do you know where that valve is?

Usually in the fuel pump assembly.

 

[2007 Denali XL]

So after 2 weeks of attempting to recreate the dying on idle issue I am giving up. I done same drive 4 or 5 times now where it occurred and apart from some very minor instability in the idle it has not failed once since my last post.

All I can think was that as it has been sitting for 4 months prior to having the trans replace something got bunged up somewhere and it has now cleared itself. I will have the fuel pump replaced at the next service just for safety sake.

Thanks for everyones feedback and help, it's much appreciated. If I ever get to the bottom of it then I will be sure to post it.

 

[OR VietVet]

I do hope it is ok now and not going to give you problems. Please do tell us if you find more info later that points to the original problem because that info is shared and used by all members here. I always like that I can pin point the exact problem and replace a part and know that I can drive my rig with confidence. In this case that may gnaw at you, I hope not though.