Failure mode - GM 8.1L / 6.0L Vortec Gasoline (HD 2001-2007, Express/Savana vans incl.)

Ignition service at mileage: coils, wires, plugs (misfire under load)

Reliability tier: aggregated - verify before ordering, see /disclosure/

Symptoms

misfire under load / rough idle at higher mileage
worn plug wires (arcing, carbon tracks) - short coil-to-plug leads on the small block, wire kits on the 8.1
routine plug service item across the run

Compare with the other causes of the same sign on this engine: misfire, rough idle, hesitation or surging

Root cause

Both engines are PFI with coil-per-cylinder ignition; coils, leads and plugs are the routine high-mileage service items. The 8.1L carries a dedicated coil/wire PN line (longer leads), the small block a shared 4.8/5.3/6.0 line.

Diagnosis

isolate the misfiring cylinder, swap-test the coil
inspect leads for arcing/tracking in the dark
plug service at the documented intervals - gapped correctly per engine

Fixes

service: plugs, wires and coils as wear dictates - OEM part numbers are on the parts list ()

spark-plug - more than one option: 6.0L Vortec Spark Plug (OEM), 8.1L Vortec Spark Plug (OEM)
ignition-coil - more than one option: 6.0L Vortec Ignition Coil Kit (OEM), 8.1L Vortec Ignition Coil 1st Design (OEM), GM Truck V8 Ignition Coil (shared 4.8-8.1 line) (OEM)
spark-plug-wire - more than one option: 6.0L Vortec Spark Plug / Coil Wire (OEM), 6.0L Vortec Spark Plug Wire Kit (OEM), 8.1L Vortec Spark Plug Wire Kit 2003-2007 (OEM), 8.1L Vortec Spark Plug Wire Kit 2001-2002 (OEM)

Prevalence

common

Parts for this repair run about $65-$150: see them next to the other repairs on this engine in repair costs.