engine seems to be running fine, cant find a vacuum leak,
i checked the resistance on all my injectors, and they were 14.
Heres the freeze frame
and the current specs at idle
Not sure where to look next
I know you checked them, but by any chance are any of the vacuum lines original at all? On my 99 I found a couple tucked away which were only mush where you couldn't see them, especially the pcv hose cluster.
Other than that do you hear a ticking? A leaky or just starting to crack exhaust manifold/gasket/coupling with the cats can be the issue.
I have a '98 that was throwing the P0171 & and the P0174.
No vacuum leaks, injectors were operating within range. No intake gasket leaks. Fuel pressure was within spec. No ticking. The cats were operating with normal backpressure.
My issue was the mass airflow sensor. Using my scan tool, the g/s were reading very low, and after cleaning the wires with CRC mass airflow cleaner, both codes went away.
One year later, both codes came back. The mass airflow g/s were too low again, and after replacing it with the OEM part both codes went away.
No issues since (3 years), and my fuel economy picked up and has stayed up around 1.5 mpg higher then before the change.
(Forgot to mention, initially it was only showing one code, the P0174)
If you have a scan tool, you should also check the short and long term fuel trims. The other bank may not be reading high enough to trip the second code.
Initially I couldn't see your freeze frames, and after trying again now I do.
As I remember, my trims were worse than yours. When both codes were finally tripped, both banks were adding 25%+ under partial throttle (50%)
I do hear a slight ticking, and I'm not sure about the hoses. It does look like someone messed with the pcv valve hose before, if that's what this hose is in the picture,
Its on the back of the manifold.
It does seem to be a vacuum leak according to this video:
https://www.dropbox.com/s/k9zacv14dgpshyx/2021-12-07%2018.06.14.mp4?dl=0
https://gyazo.com/5d98df742c8351fae2e2a1dad84befdb
That Freeze Frame data from when that P0171 code was thrown is weird. The truck was at idle.
You had a combined positive STFT + LTFT of under 5% on bank 1.
That's hardly "running lean enough" to throw that code.
However, looking at your Live Data, both of your cylinder banks are running really lean. Again, the truck was at idle.
What stands out is comparing the ECT readings between the screen captures.
The Live Data shows a cold engine. 127 degrees with high positive fuel trims on both banks.
The Freeze Frame shows a warm engine. 174 degrees with low positive fuel trims.
That seems like an intake manifold gasket leak.
The warmer it gets the smaller the leak.
Maybe hook up your scanner again and watch your fuel trims (from cold start) from when entering closed loop, to fully warmed up to see if the Positive fuel trims go down as the ECT goes up.
If it does, let the engine cool off again, and this time spray some brake cleaner or carb cleaner around the intake manifold as you watch the fuel trims on your scanner during warm up.
If the fuel trims go down, well there you go.
