robof16
April 28th, 2020, 11:26 AM
Convinced it must be a vacuum leak – multiple smoke tests, some minor leaks around TB shaft, etc. fixed and, no change. In fact, I think it is getting worse; sets the P0300 code sooner/more often.
Truck starts and runs great/strong; at WOT the injectors are at 90% duty cycle so I’m guessing it’s making pretty good power. Idle quality is actually pretty good besides the slight roughness from the misfires and the P0300 DTC. Minor work left to do on startup friction I think but that’s it.
For reference if looking at tune: 12212156 OS
6.0 Yukon XL transplant.
TBSS intake, Texas Speed Stage 2 truck cam (212/218, .550, 112+2), 92mm throttle body, 8.1L (30pph) injectors - referenced, stock manifolds/exhaust
Smoke test, no vacuum leaks, good fuel pressure, new injectors, new MAF cleaned, head/chassis grounds-serviced, old coils, relatively new plugs (iridium gapped at .040) and wires, O2 sensors recent but not new.
In the “Cruise” log the few misfires that appear are only when the vehicle comes to a complete stop, otherwise, zero. At idle, they pile up pretty quickly. Usually 2-4 cylinders have more misfire occurrences but it varies which ones so, they truly appear to be random.
WBO2 shows good AFR at idle and all other loads.
Haven’t had anyone look at tune yet so maybe something there.
Also wondering what IAC steps should be at idle? In other words, do I need to drill a hole in the blade?
Truck starts and runs great/strong; at WOT the injectors are at 90% duty cycle so I’m guessing it’s making pretty good power. Idle quality is actually pretty good besides the slight roughness from the misfires and the P0300 DTC. Minor work left to do on startup friction I think but that’s it.
For reference if looking at tune: 12212156 OS
6.0 Yukon XL transplant.
TBSS intake, Texas Speed Stage 2 truck cam (212/218, .550, 112+2), 92mm throttle body, 8.1L (30pph) injectors - referenced, stock manifolds/exhaust
Smoke test, no vacuum leaks, good fuel pressure, new injectors, new MAF cleaned, head/chassis grounds-serviced, old coils, relatively new plugs (iridium gapped at .040) and wires, O2 sensors recent but not new.
In the “Cruise” log the few misfires that appear are only when the vehicle comes to a complete stop, otherwise, zero. At idle, they pile up pretty quickly. Usually 2-4 cylinders have more misfire occurrences but it varies which ones so, they truly appear to be random.
WBO2 shows good AFR at idle and all other loads.
Haven’t had anyone look at tune yet so maybe something there.
Also wondering what IAC steps should be at idle? In other words, do I need to drill a hole in the blade?