SD injector duty and idle

[Buickquick]

I have a post here about a speed density setup on a stock 5.3L and I ran into some issues that caused me to just start over again. Since that post was made two wide band O2 sensors have died, rust I forgot to check and clean out of injector hats, fuel pump mounted probably far away from tank.
I have the fuel pump plumbed directly coming off the tank sender outlet now, removed the fuel filter, cleaned the fuel injector hats of rust, working WBO2 sensor.
2002 stock 5.3 with only long tube headers and the intake flipped backwords on speed density the IAT sensor is right behind the air filter.
The latest log and tune used for that log are included.
This engine will still not control the IAC for awhile, it took 1 min 40 sec for the idle rpm to settle and be steady. What seems odd is the injector duty cycle is already over 100% and I don't understand how unless my channels are logging math is wrong. the engine is stock with only long tube headers
I have one revision and quick smoothing of a tune based from corrections of this log it is the v8vairSD0 file

[Buickquick]

This car drives quite well on the v8vairSD0 file but I need to go drive and log it some more. The WOT pull feeling is a bit choppy its not smooth trying to figure that out but this long or almost no control of high rpm startup idle is very annoying. I don't have a way of monitoring fuel pressure while driving yet, I plan on putting a sensor in service port on fuel rail and log it with the prolink cable

[Alvin]

I have a post here about a speed density setup on a stock 5.3L and I ran into some issues that caused me to just start over again. Since that post was made two wide band O2 sensors have died, rust I forgot to check and clean out of injector hats, fuel pump mounted probably far away from tank.
I have the fuel pump plumbed directly coming off the tank sender outlet now, removed the fuel filter, cleaned the fuel injector hats of rust, working WBO2 sensor.
2002 stock 5.3 with only long tube headers and the intake flipped backwords on speed density the IAT sensor is right behind the air filter.
The latest log and tune used for that log are included.
This engine will still not control the IAC for awhile, it took 1 min 40 sec for the idle rpm to settle and be steady. What seems odd is the injector duty cycle is already over 100% and I don't understand how unless my channels are logging math is wrong. the engine is stock with only long tube headers
I have one revision and quick smoothing of a tune based from corrections of this log it is the v8vairSD0 file

I'm seeing IAC at zero with throttle at zero and yet idle is still at 2000 RPM.

You either have a bad IAC motor or a vacuum leak somewhere.


And it's still lean with the injectors over 100%. Either the injectors aren't big enough for the application or more likely I think is that it isn't holding fuel pressure at wide open.

[Buickquick]

Thanks for reading,
I have verified no intake manifold leaks on the manifold itself or manifold to heads or around the throttle body.
Only cleaned but not replaced the original IAC motor. It definitely works, seems like it doesn't respond at first for awhile then it "wakes up" The IAC mostly always parks in the 240-300 step range when cold start happens with the desired step lower in the scanner just doesn't get there for a long time.
I'll try a new or used one out to verify though.
I am with your thoughts on the furl pressure dropping during WOT I just can't monitor that yet.
The fuel tank, filler neck and cap are original and may not be venting properly perhaps too.
I'll check that out or try a drive with no cap, I definitely will order and setup a pressure sensor to log fuel pressure.

[blindsquirrel]

Mechanical gauge. Cheap. Stick it out under the rear edge of the hood, ziptie to a wiper blade or something. You don't need sending units and logging it in the scanner.

[Buickquick]

I do that now with a mechanical gauge on a 16" hose but this machine is mid engined I cannot see the gauge behind me plus the engine is sealed off from the interior. I'll come up with something

[blindsquirrel]

Video camera + mechanical gauge.

It doesn't need to be constantly monitored unless you just want to do it that way. To diagnose this specific issue all you need to do is prove that it's not dropping pressure under heavy demand.

[Alvin]

Thanks for reading,
I have verified no intake manifold leaks on the manifold itself or manifold to heads or around the throttle body.
Only cleaned but not replaced the original IAC motor. It definitely works, seems like it doesn't respond at first for awhile then it "wakes up" The IAC mostly always parks in the 240-300 step range when cold start happens with the desired step lower in the scanner just doesn't get there for a long time.
I'll try a new or used one out to verify though.
I am with your thoughts on the furl pressure dropping during WOT I just can't monitor that yet.
The fuel tank, filler neck and cap are original and may not be venting properly perhaps too.
I'll check that out or try a drive with no cap, I definitely will order and setup a pressure sensor to log fuel pressure.

The IAC doesn't report where it actually is at.. only where it is commanded to go. in that log the IAC is bad or there is a vacuum leak somwhere.

[Buickquick]

This is funny I did this underhood video job on my Buick verifying fuel pressure rise. I'll do it again on this car, I forgot about a workaround that can be utilized now. There's a removable section of the engine cover that had never been opened. I can get access to the fuel rail port for the gauge through that.
Screenshot_20230523_093108_Photos.jpg

[Buickquick]

Thanks, I am borrowing a known good IAC to swap out and test.

[Buickquick]

Good news and bad news. I won't be testing for a bit while I rebuild the transmission. Main shaft broke during the video test session for fuel pressure.
The factory fuel pressure regulator is still vacuum referenced and this test shows a good 58-60psi with some oscillation though.
https://youtu.be/DFsm7rT1Py8