Hi.
Got codes for random misfire and to all 8 cylinders.
Found some genius replaced the coils assembly and left it sitting in its place.

Bolted the assembly to the back of the block and the MIL light vanished by itself with no erasing error codes. Had obviously, poor high voltage grounding.

Read at several places the possible causes and collected them on a list :
p { margin-bottom: 0.08in; } MISFIRE CAUSES


Poor contact on fuel pump relay
Poor fuel pump wiring connections
Bad spark plugs
Bad spark cables
Bad coils
Vacuum leak in the intake manifold, sucking or whistling noise
defective Exhaust Gas Recirculation (EGR) valve
bad gasoline
dirty fuel injectors,
Injector leak, dripping
low fuel pressure,
Weak valve springs
Clogged catalytic converter -A vacuum reading that gradually drops while the engine is idling almost always points to an exhaust restriction.
An oscillating vacuum reading usually indicates a leaky valve or worn valve guides.
An EGR valve that is stuck open at idle can have the same effect as a vacuum leak.
loose positive crankcase ventilation (PCV) hose,
Leaky PCV valve
wrong PCV valve
Weak fuel pump (low fuel pressure)
faulty fuel pressure regulator
Incorrect ignition timing
Defective Mass Air Flow Sensor
Defective Crankshaft and/or Camshaft Sensor
Defective Throttle Position Sensor
Valve problems
Too low fuel level in tank

 

Thank you for reporting what the cure was.