2005 Honda Pilot COP Secondary Waveform question

2005 Pilot (3.5L). Just under 200k miles. When leaving on a family trip, It threw a code (poor cat performance I recall). Fuel trims normalish at idle, but bank 1 goes way negative (response to rich condition) under load. Half way through my trip, I have a burnt exhaust valve on Bank 1, cylinder 2.
Note, there is something going on with the EVAP which the MODE 6 is telling me, I havn't looked into yet.

Put it new exhaust valves, and aftermarket CAT on bank 1. Bench tested the bank 1 injectors using a external pump/regulator/arduino pwm micro-controller into a set of graduated cylinders: no leaky injectors, all put out the same amount of volume, spray patterns look decent. For shits and giggles, I swapped around the injectors and coils from bank 1 to bank 2. Made sure valve lash was adjusted before getting everything was back together.

After getting everthing back together, still the same story on fuel trims: Fuel trims normalish at idle, but bank 1 STFT goes way negative, -25. Tied into the fuel pressure line, and pressure is within spec. Swapped lambda sensors between bank 1 and 2, and I still get the same response on bank 1.
Did a quick scope of the injectors on the vehicle....I could see where the bank 1 injectors is shortening the pulse as result of the negative fuel trim.

So, I then turn to secondary ignition. Since this is a COP, and I didn't want to mess with variability of the COP probes, I used the Hantek wire extensions, and hooked up the typical capacitance probe on the extension wire.



I notice a discontinuity in the spark line - see red arrow this is from bank 2. Anyone know what this might be? It seems to be common with bank 2.




The two below are from a cylinder in bank 1 at idle. The norm (whether right or wrong) is a ~500V spark line, approx 1.5ms. Occasionally, there is a random jump in the spark line, as shown by the other photo - double or even quadrouple the 500V. I would have to believe this is not normal. Would this be intermittently failing coils? Cant check the primary as it is inside the COP.


Thanks in advance.

What happens to the firing kv while the spark duration time is reduced?

Basically, the higher spark kv point indicates elevated secondary resistance. Does this happen at idle only or under different conditions as well? Which ones, if so?(make sure it does not spark outside the cylinder)

At this point the coil itself would not be my primary suspect. The amp readings under both conditions look good, there is no overshoot etc.

The short burn time of around .5ms will cause misfire, what does scan data reveal? Are the misfire counters elevated for this whole bank?

Thanks for the reply. Random and a handful reported on #1, 3, and 6. (So, some on both banks). I find AutoEnginuity to be quite buggy, especially on Honda's but that's all I got.

The first post was all at idle. But I see an occasional spark line jump similarly at higher engine speed as well.

Higher secondary reistance.. could still be in the coil pack or boot (or plugs)? If I trust the old saying of everything on the left half of the spark line is outside the chamber, the possibly the coil pack assembly (boots?) Or plugs. Seems like a sparking outside the plug would also result in a much lower spark kV, no? Spark kV goes up double/triple or more when this happens.

The kV peak jumps around quite a bit...between 5 and 12 normally) at idle. It is not consistant. I can get it to see 15 under snap if I'm lucky. I haven't seen much higher than that.

Outside/inside the chamber is not a very fortunate expression (as I think about it), although often a time used ....

What this phrase primarily is about is wether an observed irregularity in the secondary is due to the dynamic,varying factors that effect the spark - compression, A/F ratio, timing - or not. Figure a carbon fouled spark plug: It's high resistance, will shorten the firing time and so on. It will show on the left half of this imaginary spark line,yet it is in the combustion chamber....

Just to make sure you don't chase a tooling issue : Does generic OBD2 show the elevated bank 1 trim as well? Do you experience lack of power?

Wondering if you're fighting a restricted EGR passage in the intake, causing more gasses to feed bank one (and thus show rich). You could try disconnecting the EGR valve and see if the fuel trims improve.

I'm very interested to hear more about your Arduino fuel injector flow tester! Do you have some links or pictures of your build?