I'm doing an LS Swap with a 5.3L out of a 2005 Silverado and I have an engine surge problem when pressing the throttle.
Fuel pressure tested at 70psi on the fuel rail while the truck was running
Checked the ground on each head as well as the block
I need some help figuring out why its surging. Any help would be appreciated
Last edited by boondocker99; 09-20-2021 at 07:19 PM.
That's too much fuel pressure, you need to dial that back to 58psi.
If everything is stock on the engine with stock fuel pressure, no vacuum leaks and a complete exhaust with both front o2 sensors it should not have any surging problems.
The log you posted shows that the o2 sensors are super lean and when you press the throttle the short term fuel trims spike really high to add in a ton of fuel.
2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.
If you don't post your tune and logs when you have questions you aren't helping yourself.
I changed the fuel pump and regulator, now I have approximately 58 psi on the fuel rail.
The bad new is the truck is still surging. Any other suggestions?
A little more info on the truck
The engine does run and idle
DBW Throttle
Manual Trans
No DTC's present
Headers
The O2 sensors are plumed just behind the header, so they are not directly in the header
I did some more testing today and found that when I reset LTFT, the truck seems to run good for about a minute and a half
That first minute and a half is OPEN loop.. Meaning the PCM is NOT using the O2 sensors to control, or adjust, fueling.. So... If it runs BETTER in open loop, then I would suggest as we suggested on your post over on Ls1 tech that you have something wrong with your O2 sensors... They are telling the PCM that your engine is LEAN and so therefore the PCM is adding a bunch of fuel based on INCORRECT data from the O2's... You can either put the tune into OPEN LOOP permanently, or figure out why the O2 sensors are not working correctly. As I posted in your other post on LS1 tech (if that was you) the O2's AFTER long tube headers is NOT going to work. You need to have the O2 sensors as close to the exhaust valve as possible. Shoot for 18" max like GM does.... Oh wait.. You have long tube headers... So... Put the O2 IN the collector OF the long tube header.. About 2" after all 4 tubes come together... Then, look here for further tuning;
https://www.google.com/search?q=how+...client=gws-wiz
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