2012 Durango Misfire Mystery

Hello all, been gone for a while,, super busy in shop and not very social to begin with lol. I'll expose my ignorance on this wave form, not sure whats going on here but I'm thinking coil driver. I've scoured the interwebs for examples but could find none. Cylinders 1 and 2 both show misfires on the counter intermittently, can't feel them most of the time. Waveforms on 1 and 2 are pretty much identical. We've moved coils and plugs around (and a bunch of other stuff before I got smart bought a pico cop "wand") Pics are off my phone as they seemed clearer than the Verdict's screen shots. Red line is current ramp green is secondary. Weird how the secondary voltage goes negative, is that indicative of a short in the primary? My gut says yes. Last pic is a zoom of Cyl1

I’m not sure but have you checked for spark with a spark tester gapped at 30kv? I know them 3.6 liters have cam and lifter problems.

Also have you went in and reset all adaptive memory under functional tests?? I’ve had to do that on a few dishes after replacing crank sensors it would still Miss after the new sensor install then reset memory and they would quit missing

Yeah, actually have had the valve covers off this one already and all is well in there, even did a leak down for good measure.

Do you have Peak Detect turned on? I'd like to see a waveform with the Secondary Voltage scale of 10-15 KV. If you save the .VSM file, you can transfer it to a computer and use ShopstreamConnect to view it on a PC. I would like a copy of the .vsm, too, if you can upload it. Current draw seems high, too, IMO. It, also, seems to be of an inconsistent pattern.

ShopStream Connect

drive.google.com/file/d/1jlkwNJ0wHFw3t6I...tpa/view?usp=sharing

I'll get you a .vsm with just the secondary tomorrow. The current draw inconsistency between the three screen shots? Or something else?

Not just Secondary. Current, too, please. (Make sure Peak Detect is ON) I would like a known good, too, if possible.

The current draw inconsistency between the three screen shots?

Yes. All three traces have a dwell of 3 ms. The top trace ramps all the way until turn-off. The other two plateau, after just 1 ms.

I know there is a zoom difference but, I can see turn-on oscillations on the bottom trace, but not the middle trace. The middle trace stands out as shorted, to me. But, but the turn-on oscillations, on the bottom trace, make me hesitate to say that IT is shorted.

I think, on these, I would do a resistance measurement, between Primary and Secondary.

I just looked at the wiring diagram for this. These are 2-wire coils. That means we can look at Primary Voltage. I would, still, like to see Secondary and Current. But, I would ALSO like to see Primary Voltage and Current. Set your Scope on a 400 V scale and back-probe the CONTROL side of the coil.

You were questioning the coil Driver. You want to see the voltage get pulled all the way to ground during turn-on. You, also, want the turn-off to be instant and complete.

Ahh, that's what i thought, the first trace is a known good. Sorry

Got some .vsm's and in the process I think I found the problem, in a previous wiring repair, the wires to the #1 and #2 coils were reversed. I feel silly for not having noticed that when I was ohm-ing out the wires!

Also, it won't let me upload the vsm's, want me to email them to you?

BetterCallBrody wrote: Also, it won't let me upload the vsm's, want me to email them to you?

There is a trick to upload the .vsm files. Just change the file extension to .psdata.
(or, any of the Allowed file extensions--- Allowed file extensions : jpg, jpeg, gif, png, txt, rtf, pdf, zip, tar.gz, tgz, tar.bz2, PSDATA)

For example: change the file name from waveform.vsm to waveform.psdata. Or, just add the .psdata extension to the end: waveform.vsm.psdata

Or, email them to me:

ssautomotive13@gmail.com

Fixed the swapped wires Friday evening and re-checked waveforms and all is good now. Can't believe the coils were even sparking, guess thats a 2 wire coil thing? Also seems like it should've been throwing a circuit code of some sort! Anyway I'm still emailing you the vsm's. Maybe you can post them here for reference, now we know what reversed coils look like.

BetterCallBrody wrote: Fixed the swapped wires Friday evening and re-checked waveforms and all is good now. Can't believe the coils were even sparking, guess thats a 2 wire coil thing? Also seems like it should've been throwing a circuit code of some sort!

That's great!

Anyway I'm still emailing you the vsm's. Maybe you can post them here for reference

Good. I'd, still like to see them.

now we know what reversed coils look like.

:woohoo: Now, I am going to have to play/experiment. Thanks for the update!