Dreaded code P0300, have a few scan shots

[th3 shifty]

Hey guys I just did the MPFI injector change last week and got it all together. I also changed the following:

Spark plugs
Wires
Cap/rotor
Intake plenum gasket
Coil and ICM

Started up the truck (96 tahoe) and started out with a really high idle, I quickly found that to be a vacuum leak from the new injector to plenum gasket area and solved it. Cleared the code started up the truck, starts as a high idle then drops to 800 and maintains. Soon after that I quickly get the P0300 code.
I have a foxwell scanner and hooked it up and found the followingsee pics)

Now I’m not good reading fuel tables are pretending to know what half this stuff is, I DO know that -22 spark advance at idle is wrong, and the motor is pulling timing to pull down the idle.

It’s only throwing 1 code, I have soaked that motor down with carb cleaner to try and find another vacuum leak but I have found one.
Any help is appreciated

 

[Fless]

It's adding a lot of fuel on both banks at that RPM; what do the STFTs look like at 1500 or 2000 RPM?

 

[OR VietVet]

Why was all the work done? On a whim or to upgrade or to address a problem? Go back and inspect your work.

 

[th3 shifty]

Why was all the work done? On a whim or to upgrade or to address a problem? Go back and inspect your work.

Almost the entire truck was original, it was starting to be sluggish and idle was starting to be poor

 

[east302]

Were those screenshots taken in closed loop (engine warmed up)? As Fless mentioned, see if the trims trend toward zero as rpm is increased. That’s usually a vacuum leak - unmetered air is coming in downstream of the MAF sensor, the computer sees too much air being reported by the oxygen sensors and is trying to add fuel to get it back to the proper fuel-air ratio. Positive trims.

The intake tubing after the MAF isn’t open somewhere, all clamps are tight?

If your scanner will do it, also see if it shows misfire counts by cylinder.

Edit: Your screenshot shows the coolant temperature (ECT) at 86 degrees. Let it warm up and see what the trims show.

 

[Hoesgottaeat2]

Couldn't hurt to pull the IACV and clean it up with some carb cleaner and throw it back in to see if that makes a difference. Costs nothing to try and it'll take (5) minutes. I know the code doesn't correlate, but the symptom certainly does. Wouldn't hurt to try.

 

[th3 shifty]

Thanks for the suggestions, I’ll get to work on those today and see what comes of it.

 

[th3 shifty]

Ok boys here’s the scoop, pulled the IAC cleaned it, no change. Got the truck up to temp as far as it would go here in 20*f weather which was 167*, fuel trims fell to 50%, and idle spark advance to -16 degrees.

Took my car cleaner spray abs started to hose down the engine around the plenum, nothing. Then started on all hoses and vacuum lines, nothing. I hit the oval top section where the new fuel connector comes up, and sure enough I have a leak there.

Now, how do you get that part to seal because I spent forever working on that part to seat

 

[east302]

I always lightly wipe the injector housing o-ring and the inside of the upper intake with oil and then put the upper intake down. Best bet is to pull it and try again or put a new o-ring on. It may have broken or just slipped out of the groove.

If you’ve already done all of that with oil, white lithium, etc. then see if the inside of the plenum is scratched or something.

 

[th3 shifty]

Good tip, no I didn’t lube it at all, so I’ll do that. Sucks I have to pull everything back out