P0174 Issue, 09 G8 GT

[donkeyGT]

Shit man...how much do you charge for labor? The boss and myself could take a road trip to CO and we could stay at your place while you (and my expertise of course) could do a DOD delete/cam swap this would be cake for what your dealing with..

[STL_G8GT]

Shit man...how much do you charge for labor? The boss and myself could take a road trip to CO and we could stay at your place while you (and my expertise of course) could do a DOD delete/cam swap this would be cake for what your dealing with..

That's not a terrible idea, but I don't tune, so that might be a tough one. I did replace one of the axle/cv shafts and seal in my truck as a break, which was nice because it was a clear start/finish kinda deal!!!

[STL_G8GT]

Wellllllllllllll

got it back together with new gaskets, new injectors, new springs, and new lifters... still drifts. However, now it starts Bank1 @ -3% and Bank2 @ 0% and then at about 16mins through 20 mins Bank1 will go to 1% and Bank2 will climb to 5.5-7%.

It seems that both banks will climb slowly, but bank 2 climbs exponentially more. These trims are significantly better than before, however the drift is still perplexing.

Things that are new:
Blower sealant
Head Gaskets
Exhaust Manifold Gaskets
Injectors
Springs
o2 Sensors
removed Cats


Inspected, no faults found:
Pushrods
Valves
rockers
piston tops
Lifter trays
Spark plug wires
Ignition Coils
Wiring and both engine grounds
Exhaust clamps/system
Tested Spark distance @ temp and @ startup, both fine
Fuel crossover @ blower

If I think about this a bit differently, because both banks technically richen up, it really could only be bottom of the engine (extremely doubtful), a fuel pump issue (as fuel rails get hot and/or fuel pump heats up), or a ridiculous wiring issue that is temperature specific (again, doubtful).

Oh well, at least she's got new springs in her!

Figured I'd circle back here once more.

Replacing all of those parts, freshening up the top end, putting in new injectors (incidentally the old ones came back from testing and ID said they're good as new), and a tune adjustment for the new injectors has the fuel trims more balanced / zeroed at idle. The long idle (20mins +) issue is still somewhat present, although greatly reduced. I did notice that it starts to drift at the 15-16min mark (idling, no throttle manipulation, in park), and then at the 25min mark the other bank starts moving as well. I can't imagine a scenario where I would ever idle it for a half hour, and even if I did, with the exception of the fuel trims adjusting, there are no ill effects. As soon as I put it in drive, and then return to park, it starts over again. I did check fuel temps at different points, and it's never high enough to truly cause an issue. I did find out that my fuel pressure gauge in the car displays 2psi higher than the actual sensor is putting out, so I adjusted the controller to 42psi at idle logged in HPT via the interface input. ( I believe it's a ground issue, although I've tried two stock ground points with no change. )

The car starts, runs, drives just fine.

I don't have any idle logs to compare to, to see if this is a newer issue or if it's always been present, but because of the way that it shows up over a LONG idle, I'm guessing that it's always been this way. The only thing that got me looking into it was the p0174 that may have been thrown because of any number of small leaks that I found and addressed, before fueling/airflow was adjusted because of the larger intake tube.

I still would like the tune cleaned up for transients, eoi, and flex fuel, but remote is the only option, and that's a real pita.