Help: 5.3 L59 Running SUPER rich

I have a 5.3 Gen III L59 that is swapped into an old Pontiac that I am just now starting to run more/drive around a little (vehicle is currently uninsured, unregistered, running open headers, no seat belts, no hood, so putting on any real break-in miles is going to have wait a little bit)

Regardless, when I do start it and let it warm up and drive it in and out of the shop, any human with a working nose can tell you it's running INSANELY rich. Now, it has a pretty substantial cam (BTR Stage 4 Truck) so I know it's normal to add a little bit past stoich to keep it happy.

But my commanded air-fuel never goes above the 12.4 range, and it smells and acts way richer still. Plugs come out black, overpowering exhaust, even flames (cold)/pops (hot) at idle. Not to mention that I have to keep changing my oil after like every 5 starts because it's so fuel-spoiled.

If anybody can tell me what parameters I should be looking at on HPTuners 3.x I would very much appreciate it.

Thanks in advance,
Devin

P.S. Since I forgot to put in original post. Before anyone asks. No I don't have wideband. I know I know...

But from what I'm getting from the stock narrow O2's- around 650-800 mV- I can safely assume a very rich state

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Originally Posted by neond123

I have a 5.3 Gen III L59 ... running open headers ...

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Having a leak in the exhaust system can drive the oxygen sensor to read as lean - causing the computer to add fuel to the maximum allowed by the calibration (typically 25% to 50% over the base amount). An open exhaust will cause this to happen on both banks.

If you need to run the engine before a proper exhaust system is installed, unplug both connections to the oxygen sensors - this will put the computer into open loop mode.

Post the tune and logs.

As said, you can't run o2 sensors with open headers, they will never report correctly. Having the commanded never change from 12.4 is something else though. I need to see what is going on and how the tune is setup to comment further.

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Originally Posted by 5FDP

Post the tune and logs.

As said, you can't run o2 sensors with open headers, they will never report correctly. Having the commanded never change from 12.4 is something else though. I need to see what is going on and how the tune is setup to comment further.

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I have 18" of extension that the O2's are sitting in, 6" after the collector, 10" after the outlet. I was under the impression this was enough. Clearly something is wrong. It starts backfiring as soon as it gets above like 130 F*


Here is the tune I'm currently running and some logs. Please note, in the logs, if it goes above the 12.x range, it's because I overrode it to do so.

Attachment 93973Attachment 93974

P.S. Popping/backfires only happen at idle (800-900 rpm) to about 1,300 rpm.
Only started about a week ago. It may be because the plugs are super fouled, but it's running too rich, causing the foul, incomplete combustion is causing more rich, etc etc. I need to stop the chicken from laying the egg.

How many times do you have to be told to unplug the O2s?

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Originally Posted by 2xLS1

How many times do you have to be told to unplug the O2s?

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The guy asked to see my tune. I gave it to him. Maybe he knows something else. Just looking for input. Thank you for your concern regarding my ability to follow directions.

Unplugging the o2 sensors will help for the time being because even with those exhaust extensions it will still skew the narrowbands.

Nothing else is stopping the commanded AFR from going up to stoich. If you aren't running a flex fuel sensor, just set the whole stoich table to 14.68.

I see it has larger injectors, what are they and did they come with data? There is far more to injector data than just the flow rate change.

If you have a wideband, get it working and into your scanner logs. That is how you will be calibrating the MAF and VE tables to correct the fueling.

Quote:

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Originally Posted by 5FDP

Unplugging the o2 sensors will help for the time being because even with those exhaust extensions it will still skew the narrowbands.

Nothing else is stopping the commanded AFR from going up to stoich. If you aren't running a flex fuel sensor, just set the whole stoich table to 14.68.

I see it has larger injectors, what are they and did they come with data? There is far more to injector data than just the flow rate change.

If you have a wideband, get it working and into your scanner logs. That is how you will be calibrating the MAF and VE tables to correct the fueling.

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The injectors are 2009 flex fuel injectors. I don't know the part numbers off hand. 36 lb/hr GM OE
I didn't change any parameters except for the flow rate. 😬😬

And no, I'm not running flex right now, just 93. I disabled the option on my tune but I'll set the AFR-Ethanol % table to stoich and see what it does.

I disconnected the O2's when I started it tonight and it seemed to smell less pungent and backfire a little less. Still a decent bit, but less.

No wideband right now :/, get paid next week. Will invest in an AEM.

UPDATE: Updated open loop stoich tables, didn't touch the EQ. Its commanding stoich now so that's very good. Still running open loop no O2's. It doesn't backfire as much at idle. But when you gas it driving and then come to a stop and it drops back down it really starts popping for a while. Is this just an open header thing? Im going to run straight pipes (mufflers are expensive) with an X crossover to see if the added scavenging helps with the backfires.

Update the rest of the tune with the correct injector data.

Use this excel spreadsheet to copy the 2009 data into the spreadsheet so it can spit out the LS1 based injector data. Then copy paste that into the tune so everything jives.




Pops and crackles with no cats and just headers is normal. You're going to hear all the noises while off throttle and when DFCO kicks in and out.