07 yukon xl 6.2 stalls at hot idle and wont restart

[xdieselmechanic]

I apologize for long post put going to try to explain everything.

Parts replaced so far:

Cam sensor

Crank sensor

Cam phaser valve

Cam phaser solenoid

Fuel pump

Maf

1 injector

Pcm

Pdm

 

So about 2 weeks ago coming off the highway my 2007 yukon xl with the 6.2 stalled and would restart. Had unit towed back to house and I messed around with relays and unit started. Drove it the next day and same thing. Had it towed again. Scanned unit and had code p0300 with misfire data showing mainly cylinder 7 but I know that won't cause a no start. Measure fuel pressure and found only 42 psi replaced pump to have unit stall again and not restart. This time I stayed on back roads and just waited for it to restart about 30 to 60 min. During this time I found I have no injector pulse but have good power at injectors. Started unplugging 1 injector at a time and found when unplugging cylinder 7 pulse came back so i changed injecto and same issue. Turns out unit just happen to ready to start at that time. Scanned into unit and found no reason for the pcm to take away injector pulse so I replaced the pcm and same issue. I figured timing sesnor controlled the injector pulse so I replaced both sensors and while I had the water pump of i replaced the vvt components while i was in there. Read multiple people have luck chaging the maf for this issue so I changed it. Unit still stalls to this day and loses injector pulse on the ground side when it does. Have noticed watching the live data the pcm is request injectors to fire via injector pwm value. I have redone the ground wires at the left bottom of the block knowing this was the ground location for the pcm but still no luck. I am a mechanic by trade but this is having me pull my hair out. If anyone has something to have me check I will gladly im not much of a parts thrower but im about to load the cannon

[xdieselmechanic]

Forgot to mention that this started after changing the oil I use mobile 1 full syn with mobile one filter but I did add pro lube additive and was the first time doing so and is making me wonder just can't see why that would matter

[Jsdirt]

Holy s**t - not much of a parts thrower you say? You BLASTED that thing with the parts cannon!  You'd have been probably $1,000 ahead if you had just brought it to a competent shop rather than shotgunning a bunch of parts it clearly didn't need.

 

Just FYI - oil additives are really, REALLY good at ONE thing ... and that's emptying your wallet. They're ALL useless gimmicks.

 

If that has the L94 or L99, then #7 is an AFM cylinder. I'd suspect a failed lifter in that case.

 

If you leaned on wiring, sensors, and/or connectors while changing the oil, you'll have to check all that to be sure pins didn't get pulled out, connectors broken, etc.. Old wire loom that was barely adequate when new is certainly brittle by year 19 - make sure wires aren't chaffed and shorting out somewhere where you might have leaned. or supported yourself on it.

 

If your a mechanic, why didn't you just find out what you were missing and troubleshoot from there??  TIMED spark, fuel PSI / injector pulse, air, compression.  Can't make ANY money going the parts cannon route.

[asilverblazer]

15 hours ago, xdieselmechanic said:

...no injector pulse but have good power at injectors. Started unplugging 1 injector at a time and found when unplugging cylinder 7 pulse came back so i changed injector and same issue... Unit still stalls to this day and loses injector pulse on the ground side when it does. Have noticed watching the live data the pcm is request injectors to fire via injector pwm value. I have redone the ground wires at the left bottom of the block knowing this was the ground location for the pcm but still no luck.

Are ALL injectors losing ground or just #7. Sounds like a wiring problem to me.

[xdieselmechanic]

6 hours ago, asilverblazer said:

Are ALL injectors losing ground or just #7. Sounds like a wiring problem to me.

All injectors are loosing the ground side from the pcm even with all injectors unplugg there is still.no ground pulse on any injector

[Jsdirt]

PCM powers and grounds - EVERY one of them has to be good. Since PCM replacement didn't fix it, then all of these need to be good, AND the ground from the computer to the injectors needs to be checked end-to-end.

 

I use halogen headlight bulbs to test powers and grounds. Puts a decent load on the wiring. If they can light up that, then they'll run what they need to run.

 

If you can get the computer to ground and light the bulb using a short jumper, then the wire is bad to the injectors.

 

Also make sure a pin didn't get bent over when plugging the computer connectors back in, and that the female terminal puts enough tension on the male terminal to achieve continuity AND the ability to carry a load.

Edited July 31 by Jsdirt

[davester]

computer pulses the injectors by connecting them to ground (at least on the trucks), so they get constant power...