Misfire with no check engine codes on 2006 H6?

[idosubaru]

How do you diagnose a light misfire with no check engine light?

2006 Tribeca 210,000 miles, new plugs and air filter. Constant light misfire. 

Runs and drives fine as a daily driver, seems to under perform a little which isn't ideal as it's my main tow vehicle. 

[heartless]

might be a wire(s) on its way out??

those are the coil on plug type, correct?

but yeah, kinda hard to know which with no CEL giving an indication of which cylinder is the problem

have you checked for any arcing in the dark?

[1 Lucky Texan]

NGK plugs?

[idosubaru]

1 hour ago, 1 Lucky Texan said:

NGK plugs?

Yes. OEM. 

Edited August 1, 2020 by idosubaru

[idosubaru]

21 hours ago, heartless said:

might be a wire(s) on its way out??

those are the coil on plug type, correct?

but yeah, kinda hard to know which with no CEL giving an indication of which cylinder is the problem

have you checked for any arcing in the dark?

COPs, so no wires.  haven’t checked for arcing. Maybe I should pull COPs and checks for oil leaks but there’s not a drop of oil anywhere and no CEL so I doubt it’s that.

Im wondering if I can pull data, freeze frame, if that’s easy enough to do in a situation like this. Look at throttle, O2, etc.   

Edited August 1, 2020 by idosubaru

[1 Lucky Texan]

wonder if a light stream of propane fed in the intake while idling would make a change in the symptom? might exonerate or prove a fuel issue instead of spark???