Stock 5.3 swap, flooding out commanded AFR's very low

[93c15005.3]

Hey guys, complete newbie here. I did an LS swap into my 93 c1500, just a 100% factory 5.3 swap. I made a stand alone harness and only tuned VATS out of the P59 ECM but I cannot get this engine to run or idle. Sometimes it will fire and I can pedal it for a few seconds but then dies, plugs are soaked and its flooded. VCM scanner shows my injector pulse width is through the roof, sometimes 50+ms and commanded AFR's as low as 3-4. I've tried playing around with some tables but can't get it to run. I downloaded a stock tune file off here and used the compare function and cannot find any differences between the two files.

I am waiting on a different set of exhaust manifolds to complete my swap so for the time being I am using open truck manifolds with only the passenger side upstream o2 sensor connected via a 8 inch section of pipe, driver side manifold runs to close to the frame to get any pipe with a o2 bung connected. I don't think this would cause this issue, I had another vehicle with a gen 3 5.3 (stock silverado) and unplugged all but its passenger side upstream and it idles, just not too happy.

I attached two files, one file is when the engine did fire for a few seconds and die, the other is me cranking it when it is flooded. Any help would be greatly appreciated, this truck has taken up my garage for far too long.

[93c15005.3]

Sorry just noticed my "engine did fire" log had the MAF unplugged, that was something I tried and didn't work. The truck acts the same with the MAF plugged in or not, right now I have to wait for the engine flooding to clear before it will start again to make a new log file with the MAF plugged in.

[blindsquirrel]

Intake restriction? MAP drops from 99 at KOEO to 97 just from turning 160 RPM on the starter.

You need to post the tune file, too. If I had a dollar for everybody who came on here and swore up and down there were no mistakes made in the tune file, no way no how, and it turns out they changed stuff they didn't understand or even remember changing...

[93c15005.3]

I'll check for intake obstructions, I tried both the factory intake and a cold air intake system and both cause the same issue. I'll attach both the as found tune and the vats delete tune I made. I have played with the tune to try and solve this myself but I ultimately end up using my "vats delete" tune after each attempt to fix it. I bought the motor, trans, harness and computer as a package deal and was told it was just a factory drop out, no tuning or performance parts added. My "vats delete" tune is the file as I received it with vats turned off and a write entire flash done.

[blindsquirrel]

You reused all the flex fuel sensor/wiring and stuff in the swap? ABS/EBCM/RSS/DIM/etc, and other parts the stock truck would've had that you now probably don't? Because flex is still enabled and DTCs for all those things are still on ('No MIL' still runs the diagnostics and can trigger other actions when they fail or can't complete). Theft deterrent DTCs still on, too.

[93c15005.3]

No, no flex fuel was used in the swap, the harness was depinned for all flex fuel, evap and rear 02's. I wrote a tune to turn off flex fuel and get rid of all DTC's, flashed it in and still nothing. The engine hit a few times but would never catch and idle. I've attached the new tune and log file for that attempt. When removing DTC's I have been simply unchecking the boxes, do I instead need to change the options on the far right to no error reported?

VATS DELETE+flex fuel+DTC's.hptvats+flexfuel+dtc delete log hits but no start.hpl

[blindsquirrel]

Unchecking the box only stops a code from turning on the light, all the related diagnostics and actions still happen. To disable something the code has to be changed to No Error Reported.

I wish I knew the reason for the No MIL Light option, but from all the searching and reading and even directly asking I have done, nobody has been able to explain it. It's not in a sticky' thread anywhere, it's not ever mentioned anywhere in the GM service manuals (kinda obviously), it's not in any of the HPT help documentation.

[blindsquirrel]

Do you have a lack of fuel, or too much fuel? How would you check for conditions like that??

screenshot.25-03-2024 05.09.50.png

[93c15005.3]

The computer is commanding too much fuel, the brand new spark plugs I put it when doing the swap are already black and when it won't start and I pull the plugs out they are dripping with unburnt fuel. Command afr shows way too rich and injector pulse width are way too high. Something in the computer is telling the engine to push way too much fuel in and I can't figure out what setting or sensor is causing that. I reached out to a guy I know with hptuner experience and he said the oxygen sensor not reading right could cause this. I should have my new exhaust manifolds this week and will get them installed and retest, I'll update with any results.

[Alvin]

I don't see anything in your log but you should also be scanning more.

Disable flex fuel if you aren't using it. log MAF. Even the default pids HPtuners loads would be more helpful than this.

[edcmat-l1]

IAT.jpg

I'd start with the obvious first.

In your one log where it did fire up, the injector pulse width did come down to a reasonable value/range when it was running for the few seconds it did.

Fix the IAT (plug it in), pull the plugs, disable the coils and injectors, crank it through. Put new plugs in it, then see what it does.

Might wanna change the oil too if it smells like fuel.

[jsf55]

And 53 psi for the fuel pressure if your using aftermarket