Weird very lean condition on LS3
05-26-2017, 12:05 PM
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Weird very lean condition on LS3 Hey guys, I'm tuning a 1954 chevy pickup with a GM LS3 525 hp crate engine swapped in and a pre 06 4l60e. The guy who did the swap got the ecm/tcm and wiring harness from PSI Conversion and it's a 2008 Silverado e38 ecm.
I am getting some really weird lean conditions. At warmup in open loop with my wideband in a narrowband bung, the wideband is reading 1.29 lambda or 19.5 afr, the leanest that the wideband will go. The electric fan comes on at 195* and the INSTANT the fan kicks on the wideband goes very close to stoich and is perfectly normal. The other weird issues though are that at decel (DFCO disabled) it goes full lean and when I tried to go wot, the afr goes from stoich while cruising to 19.5 afr lean on my wideband at wot. It immediately was popping and sputtering, so I let off. My lambda vs maf error histogram showed 70% error at wot lol. Something is definitely off.
Any ideas on what this could be? I've checked fuel pressure and it is 58 psi at the rail. I've checked for vacuum leaks around the intake and there is nothing to be found. I've checked for loose grounds, checked spark plugs, checked injectors to make sure they are indeed stock LS3 injectors and they are. I'm stumped on this. At this point, it seems like something electrical related since the fan kicking on makes the afr normal, but that doesn't explain it at wot. Could it be a harness issue with the PSI Conversion harness? I've read where they have been known to pin things wrong in the past. If anybody has any input, please let me know. Thanks.
I am getting some really weird lean conditions. At warmup in open loop with my wideband in a narrowband bung, the wideband is reading 1.29 lambda or 19.5 afr, the leanest that the wideband will go. The electric fan comes on at 195* and the INSTANT the fan kicks on the wideband goes very close to stoich and is perfectly normal. The other weird issues though are that at decel (DFCO disabled) it goes full lean and when I tried to go wot, the afr goes from stoich while cruising to 19.5 afr lean on my wideband at wot. It immediately was popping and sputtering, so I let off. My lambda vs maf error histogram showed 70% error at wot lol. Something is definitely off.
Any ideas on what this could be? I've checked fuel pressure and it is 58 psi at the rail. I've checked for vacuum leaks around the intake and there is nothing to be found. I've checked for loose grounds, checked spark plugs, checked injectors to make sure they are indeed stock LS3 injectors and they are. I'm stumped on this. At this point, it seems like something electrical related since the fan kicking on makes the afr normal, but that doesn't explain it at wot. Could it be a harness issue with the PSI Conversion harness? I've read where they have been known to pin things wrong in the past. If anybody has any input, please let me know. Thanks.
05-26-2017, 01:02 PM
#2
I bet it has something to do with open vs closed loop
Hey guys, I'm tuning a 1954 chevy pickup with a GM LS3 525 hp crate engine swapped in and a pre 06 4l60e. The guy who did the swap got the ecm/tcm and wiring harness from PSI Conversion and it's a 2008 Silverado e38 ecm.
I am getting some really weird lean conditions. At warmup in open loop with my wideband in a narrowband bung, the wideband is reading 1.29 lambda or 19.5 afr, the leanest that the wideband will go. The electric fan comes on at 195* and the INSTANT the fan kicks on the wideband goes very close to stoich and is perfectly normal. The other weird issues though are that at decel (DFCO disabled) it goes full lean and when I tried to go wot, the afr goes from stoich while cruising to 19.5 afr lean on my wideband at wot. It immediately was popping and sputtering, so I let off. My lambda vs maf error histogram showed 70% error at wot lol. Something is definitely off.
Any ideas on what this could be? I've checked fuel pressure and it is 58 psi at the rail. I've checked for vacuum leaks around the intake and there is nothing to be found. I've checked for loose grounds, checked spark plugs, checked injectors to make sure they are indeed stock LS3 injectors and they are. I'm stumped on this. At this point, it seems like something electrical related since the fan kicking on makes the afr normal, but that doesn't explain it at wot. Could it be a harness issue with the PSI Conversion harness? I've read where they have been known to pin things wrong in the past. If anybody has any input, please let me know. Thanks.
I am getting some really weird lean conditions. At warmup in open loop with my wideband in a narrowband bung, the wideband is reading 1.29 lambda or 19.5 afr, the leanest that the wideband will go. The electric fan comes on at 195* and the INSTANT the fan kicks on the wideband goes very close to stoich and is perfectly normal. The other weird issues though are that at decel (DFCO disabled) it goes full lean and when I tried to go wot, the afr goes from stoich while cruising to 19.5 afr lean on my wideband at wot. It immediately was popping and sputtering, so I let off. My lambda vs maf error histogram showed 70% error at wot lol. Something is definitely off.
Any ideas on what this could be? I've checked fuel pressure and it is 58 psi at the rail. I've checked for vacuum leaks around the intake and there is nothing to be found. I've checked for loose grounds, checked spark plugs, checked injectors to make sure they are indeed stock LS3 injectors and they are. I'm stumped on this. At this point, it seems like something electrical related since the fan kicking on makes the afr normal, but that doesn't explain it at wot. Could it be a harness issue with the PSI Conversion harness? I've read where they have been known to pin things wrong in the past. If anybody has any input, please let me know. Thanks.
05-26-2017, 01:09 PM
#3
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I was originally running closed loop though and the LTFTs were maxed out 25% error lean. It did the same exact thing in closed loop and would run really lean if you cleared the trims while idling until the trims learned.
05-26-2017, 02:51 PM
#4