Autonerdz forums

Hey guys,

My name is Russ and I am new to the forum and to the picoscope. Starting to get the hang of it but still have much to learn. I am going to share some waveforms that I collected today, hope you guys can shed some light on what I have found today.

We are a small motorcycle dealership and we have a customer with a 2008 Yamaha R6S track bike. It has a high speed misfire/stumble but will only do it when at full engine temp (above 210 degrees) and about 140 MPH.

I put a channel "A" on the cam I.D. sensor. (cam position sensor) I do not see any fault with this sensor. I see a regular square wave that is consistent and regular.

Channel "B" is on the crank position sensor and I see some variations but not seeing anything thats really jumping out at me.

Channel "C" is a 20A amp clamp on the primary wire going to the ignition coils. I have all four on this clamp so that I can see the ignition pulses on all cylinders to see if the stumble is all the cylinders or just one or two. I was able to get it to do a small stumble and I can do my best to point that out on the waveform but I feel like you guys will see it.

On my dyno when the stumble gets bad enough I will see a 40hp drop in power.

I am anxious to see what you guys think.

Pleasure to meet you guys and thanks in advance! 

Wiring diagram attached and I will do my best to drop the waveforms in the dropbox.

This waveform I added channel "D" for battery voltage. I wanted to make sure the battery was not being overcharged and sending too much power to the ECU. (I had this very problem on an atv earlier this year that was causing ignition breakup)

I have uploaded this file to the dropbox under Redline Russ folder. Too large to post here.

Spence, thanks for the response. When I get to the shop tomorrow I will take a look but from what I remember I tried to get it to increase the sample rate but for some reason it would not go above 4 micro seconds (4us, correct?) if I am remembering that correctly as it is all very new to me.

Maybe if someone is willing to help get the right settings to capture the event properly that would be great!

Is there a way an admin can move this topic to the member area so I dont clutter things by reposting?

RedlinePowersports wrote on Feb 14^th, 2017 at 10:01pm:


Done

RedlinePowersports wrote on Feb 14^th, 2017 at 10:01pm:


You have requested 5 million samples and that's what you got.  Just need to step on the gas a bit more. 

Not bad though.  You appear to have captured the problem.

This is CD ignition, so the coil fires on an expanding magnetic field.  Hundreds of volts are applied to a grounded primary to make the field expand quickly and induce secondary voltage.

What I see late in your capture is that the cylinder after the CID is consistently missing it's primary current spike.  I would have to conclude that coil is misfiring.

Would be interesting to see secondary with the primary voltage and current to see where spark time is in relation to the other signals.

I have converted your oxps file to pdf and attached so more can view it.

Wow guys you caught those missing spikes and I never knew that was there...what steps did you do to get the scope to show you that?

Secondly, if they are missing the current spikes that would not be the coils fault...that would be the current signal being sent to the coil correct?

This bike does have 3 new coils on cylinders 1-3 and 1 on cylinder 4 that the customer said he recently replaced.

RedlinePowersports wrote on Feb 15^th, 2017 at 11:04am:



I would be leaning towards the coil but the secondary would be something I would like to see. I will dig up some pictures of what I have used for COP(coil on plug) secondary captures. Having your hand there at 14,000 rpms can be unnerving at times.

Do you have any silver metal tape?

Will do! Yes I do have some tape. I will definitely try that!

Spence wrote on Feb 15^th, 2017 at 12:04pm:


Exactly! 

Tom, Thanks!

If you guys had not directed me and had not spotted that, I am not sure I would have solved this.

It would seem that is a #4 bad coil. It tests fine with a meter. Book calls for 4.8-7.2K ohms and it tests at 7.0k ohms but is missing on the screen as you pointed out.

I switched cylinder 4 coil with cylinder 3 and the problem transferred!

I would say that proves that the coil that appears to be good with the meter is proven bad with the scope wouldn't you guys agree?

I am pretty confident with this diagnosis. I am also confident that this would not have been found without the Pico.