Autonerdz forums

Hi Kevin,

I have not encountered that issue.  I think using tinfoil to shim the clamp around the lead should be very helpful.  Try that and let us know. 

The other issue I'm not clear on is if you are placing the pickup on the plug wire or the coil wire.  With distributor ignition, you will only see the complete secondary picture on the coil wire.  You can then trigger off of a plug wire using an inductive clamp on the external trigger port, or the other channel, so you can focus on the cylinder of interest.  (Note:  the capacitive secondary pickup will not trigger the external trigger because the output is negative and the external trigger is a fixed positive trigger at around 2V.)

Anyway, if you are on the plug wire and the plug breaks down under load the signal may fall below your trigger point and you may not see much useful info anyway.

Hope this is helpful.

Hi Kevin,

If you email me some psd files of your captures, I can take a look at your settings and see what you are seeing.  Might be able to offer some suggestions.

Mac's COP III works fine with the Pico.  It's only attenuated 10:1 though, so you won't see the full primary spike.  The primary spike has no real diagnostic value anyway, so it's not a big loss.   



Here is a capture of a 3.0 Chrysler firing order 123456.  Channel B (top) is an RPM 80 inductive clamp on #1 wire.  Channel A is coil wire secondary parade.  One of the disrtibutor towers has a grounded test light in it instead of the plug wire.  The game is to identify which one. 

Triggering this way divides the sample rate in half on the 212/3 because we are using both channels.  A good altenative is to use the inductive clamp with the external trigger and then using only one channel.  This gives full sampling to the secondary capture, while still triggering off #1.  You cannot use the capacitive secondary pickup on the external trigger though because the ext trigger is a fixed 1-2V pos trigger.  The secondary is a negative spike so the ext trigger won't see it.   

Also, I wanted to point out the nice detail of those patterns, even though your at a relatively slow timebase.  The coil turn on oscillations and the turn-off oscillations are both there...some scopes won't even display this unless the timebase is sped up, but then you can only look at one or two firings.  This would be cool to zoom in on the burn lines, turn-on and turn-off oscillations.  Later, Matt.

Well then, I'm going with cylinder #4.  It has a lower and longer spark line.  I would like to see that one zoomed in.  The zoomed sequence you posted looks good, to me.  It is a tad difficult to see with the 20ms/div timebase, but it still sticks out to me.  As a dumb question, why isn't the firing line lower?  Were there issues inside of the cap also?  Thanks, Matt.  Give the full details weather my answer is right or wrong, please.   

Very good, Matt.  You are correct.  Here is #4 zoomed:



There may have been a little cap and rotor wear but not bad.

If you were using PicoScope, you would have simply zoomed and then scrolled through the capture to see them all up close like this.  Good eye 

Yes, the 'Greatest Gap' is in the cap on cylinder #4.  At this time base using both channels though you can't rely on capturing the full kv spike every time.  You have a sample every 20us.  Firing lines can be only 10us.  So, we are really pushing it here.

Hi Kevin,

That's a nice bunch of captures.  You are a quick study!  Here is one we thought would make for a good discussion.  I'm off to the Vision Conference tomorrow but will post zooms on any areas, as requested, when I get a chance



Note the trigger settings.  He has used the external trigger on #1 to devote the full sample rate to one channel while still syncing the capture for cylinder ID.

He has his samples turned up to 32.000 so at 5ms/div, he is sampling at 375,000 samples per second.  This means that there is a sample every 2.7 millionths of a second.   This is fast enough to display every max kv event and all the detail needed.

For comparison, a Fluke 97/98, at this time base, would be sampling at 6104 samples per second (true sample rate)  Pico is over 61 times faster!

Ok, enough math.  My head hurts.

I'll let you take it from here, Kevin.  The game is, what's wrong with the car?

Wow, it says misfire (singular) present I suppose #1 could be lean from the pattern but the rest look like cylinder turbulance (engine mecanical or vacuum leak) to me but can't be, not on all cylinders? EGR probelms? But I'd be surprised if the EGR did that to all cylinders on a snap throttle. I have seen some Ford COP coils with carbon tracking inside the coil cause a pattern that looks like turbulance but I assume this nissan (no year or model) is 1 coil? I'm anxious to know the answer.