01Blackerado

iTrader: (4)

Hey gang, long time no see here. I have an 07 GMC Yukon Denali XL with the 6.2L engine. For some reason, after driving for an extended period of time at somewhat high speeds ( 70 - 80 MPH), and coming to a stop, the truck will die when it reaches idle. The RPMs will start to bounce and surge until it finally goes to 0 and shuts off. I have been scanning with EFI live, and trying to pinpoint the issue. So far, I have replaced:

* Fuel pump
* both O2 sensors 1 (bank 1 and 2)
* MAF sensor
* crankshaft and cam sensors

The strange thing is, it doesn't throw any error codes when this happens. It's as if the PCM has no idea that there is an issue.

Another strange thing. Im seeing that the cam phaser control circuits for bank 1 on the intake side, is the only one that is NOT in a failed state.
* Intake Cam Phase Bank 1 Control Circuit: Passed
* Intake Cam Phase Bank 2 Control Circuit: Failed
* Exhaust Cam Phase Bank 1 Control Circuit: Failed
* Exhaust Cam Phase Bank 2 Control Circuit: Failed

Even with these failed states, there are no SES lights on and no pending codes either! What the heck am I missing?

Oh also, when the truck dies at idle after the long drive, it is almost impossible to get it started again. It ACTS like it's a vapor lock issue. I have to floor the pedal, to kill the injectors, crank the engine once, then release the pedal, and crank it again to get it started. Sometimes I need to repeat this process to get it started again... or just wait several hours.

Thanks all, appreciate your time and wisdom as always...

1FastBrick

iTrader: (17)

Just did an 07 Tahoe a few months back that would intermittently run like garbage. and only got worse. When it did run correctly, everything checked out. Almost seemed like it wasn't getting fuel.

Finally ended up put an ECU in it and all is well except the Catalytic Converters that it killed... Owner still trying to source a reasonable set.

01Blackerado

iTrader: (4)

I was afraid of that... I guess it would be the next cheapest thing to replace lol. Thanks for the feedback, I wish GM didnt complicate these trucks... I miss the LT/LS days when the trucks just worked...

smokeshow

iTrader: (16)

Better get a look at fuel pressure... As for the failed circuit diags, that's expected...there is only one phaser since one cam has exhaust and intake lobes for both banks on it.

1FastBrick

iTrader: (17)

Unfortunately, AT least on the one I worked on, the fuel pressure starts to drop as a secondary Issue.

We dropped the tank and replaced the pump with a known good pump to rule it out.

Dropped the catalytic converts to make sure they weren't clogged causing excessive back pressure.

All the sensors worked properly when it was running correctly too.

smokeshow

iTrader: (16)

Well its CA, you're supposed to crush the vehicle and buy an EV at the first sign of a problem.

1FastBrick

iTrader: (17)

There you go, As long as we can't see or monitor the pollution, It doesn't exist...