Hi All,
I am not a fan of secondary ignition diagnostics. I am of the firm belief that one thing can look too much like another.
When I look at the #5 pattern it looks like to me it could be caused by a poor injector spray pattern. (as Romain pointed out)
When I look at the #5 pattern it looks like to me it could be caused by EGR turbulence (as Romain pointed out)
When I look at the #5 pattern it looks like to me it could be caused by turbulence from a valve sealing issue. (as Romain pointed out)
When I look at the #5 pattern it looks like to me it could be caused by a loose spark plug.
When I look at the #5 pattern it looks like to me it could be caused by carboned valves soaking up fuel on #5.
When I look at the #5 pattern it looks like to me it could be caused by maybe something else that doesn’t occur to me.
Personally the only thing I believe it’s possible to see for sure in secondary ignition patterns are patterns of normal, high and low resistence.
When I take a look at #5 pattern all I feel confidant in saying is that I see high resistance in the burn line. However since Carl seemed to highlight the rotor gap I’ll do what I don’t like to anyway and take a SWAG and say:
When I look at the #5 pattern I see high resistance in the burn line that looks like to me it could be a crossfire to another cylinder ......or it could be something else that doesn't occur to me.
If block learn of 128 is 0 LTFT then I guess 158 / 128 = 1.23 would mean an LTFT of +23% ? The clues from the block learn if Edwin and I are doing close conversions sure don’t add up though. I'll have to go along with Edwin here. A +23 or +26 sure indicates a lambda issue that could easily be single cylinder lambda related misfire. Maybe this truck has another bank 1 issue totally unrelated to the misfire. I don’t see an ignition misfire causing this much +LTFT
Darn! I hate trying to do this with secondary patterns. They make me SWAGGER
Personally when it comes to misfires give me a vacuum guage,O2 waveforms, and most times FT’s (but even better a gas analyzer) any day