99 Tahoe 5.7 vortex P0300 code HELP

[Fless]

Is your warm engine idle 800 rpm? 30° C is not quite 90°, so the idle should come down after being fully warmed up.

The higher idle in your readings will affect the MAF reading. The MAF may be over-reporting the air that is coming in, but the engine needs to be at operating temp and at a good idle to be able to tell. At warm (correct) idle the MAF reading should be very close (in g/s) to the engine displacement in liters.

Can you get it warmed up and show us the ECT, MAF, and idle speed then?

I don't think that speaks at all to what seems to be a lean fuel condition on what looks like Bank 1 (?), but I don't understand where all the different short term fuel trim readings are coming from. There should be one reading for Bank 1 and another for Bank 2. Where are all of these O2 sensors?

 

[Mackb23]

Sorry for the late response, been a busy week but here’s an updated data screen to temp

 

[Mackb23]

Could it be my fuel injectors are bad? Again though, I didn’t have this problem before I changed the engine

 

[Mackb23]

This is a brand new spark plug from cylinder 1, 1 of the cylinders that I’m getting misfires at

 

[Fless]

The short term trims show that it's dumping fuel into both banks (Bank 1 more than Bank 2, but both excessive) so the O2 sensors are telling the engine computer that it's running lean and to give it more gas.

Is the intake intact and sealed from the engine air filter all the way to the throttle body, with no leaks?

Is the exhaust system intact?

It would be very helpful to see the MAF reading in g/s at idle, fully warmed up, along with the idle speed a the same time.

 

[Mackb23]

The short term trims show that it's dumping fuel into both banks (Bank 1 more than Bank 2, but both excessive) so the O2 sensors are telling the engine computer that it's running lean and to give it more gas.

Is the intake intact and sealed from the engine air filter all the way to the throttle body, with no leaks?

Is the exhaust system intact?

It would be very helpful to see the MAF reading in g/s at idle, fully warmed up, along with the idle speed a the same time.

 

[Mackb23]

And yeah as far as I can tell everything is intact and no leaks as far as intake and exhaust goes

 

[Mackb23]

I did look inside the throttle body and it’s pretty gonked up rhough

 

[Fless]

The MAF is over-reporting; at hot idle it should be closer to the engine displacement, likely no more than 6 g/s or so. Clean it or change it to a known good one to see how much the STFTs change. But I think there's more going on here.

When it's hot and you raise the idle to 1500 or 2000 rpm, what do the STFTs look like?

 

[Mackb23]

The MAF is over-reporting; at hot idle it should be closer to the engine displacement, likely no more than 6 g/s or so. Clean it or change it to a known good one to see how much the STFTs change. But I think there's more going on here.

When it's hot and you raise the idle to 1500 or 2000 rpm, what do the STFTs look like?

I’ll have to check that and get back with you tomorrow.. so everything I’ve done since replacing the engine, new wires, new spark plugs, new distributor, cap and rotor, pcv valve, map sensor, ignition coil, I think that’s it so far