Ignition waveform analysis

Caleb Technician Mishawaka, Indiana Posted   Latest  
Question
AESwave
ATS - Automotive Test Solutions
Pico Technology
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Driveability
2014 Chrysler Town & Country 3.6L (ERB) 6-spd (62TE)
P0302 - Cylinder 2 Misfire Detected

Hey guys Im gonna start out by saying I have hardly ever used Secondary Ignition as a diagnostic aid because I have never had equipment that I trusted. I got this 14 Town and Country in tonight with a dead miss on #2 when power braking in the bay. I know I need to go to training but I pay for this site so I figured I would post this up. Im not looking for an answer as to what is wrong as much as how you interpret the waveform and why. It was late I hooked up to the #2 coil trigger which is our problem cylinder. Also hooked up to Cyl. #1 as a known good reference. I will post 2 screen shots during the powerbrake and it was a dead miss on #2 at the time. I have measured the burn time on both screenshots for the different cylinders. I am using 10:1 anntenuators on both channels. 

Channel 1 Cylinder 1

Channel 2 Cylinder 2

diag​.​net/file/f2abhsz5t…

diag​.​net/file/f7h77hh3k…

I have also attached the Pico file.

diag​.​net/file/f3mj72vtd…

Ready to listen and learn.

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Brandon Diagnostician
Reading , Pennsylvania
Brandon Default
 

I’ll download in the morming. 👍

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Caleb Technician
Mishawaka, Indiana
Caleb Default
 

Thanks Brandon

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Randy Diagnostician
Glendora, California
Randy Default
 

If you split your firing line first part is out side cylinder . That is good . So it is not ignition . Do more in cylinder testing

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

I'm 47 and never really learned Secondary analysis either. It was a "thing of the past" when I started in civilian repair. Have you watched the (looong) video here?; youtube​.​com/watch?v=yCchGN… I think you are seeing turbulence on the red trace. And since this is a Chrysler, which means we know the head is bad, that makes sense. :-)

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Caleb Technician
Mishawaka, Indiana
Caleb Default
 

Hey Geoff. Yes I watched that video but it was about a year ago lol.

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

I think I started it three years ago and haven't finished. I did, however, remember the scene with Jim blowing air onto the spark generator. (unless that is a different video!) Think of it like blowing lightly on a candle; the flame jumps all over; ya know? (rhetorical)

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Randy Diagnostician
Glendora, California
Randy Default
 

Yep you are correct

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Joe Diagnostician
Jersey City, New Jersey
Joe Default
 

Hey Caleb ,you 100% have turbulence caused by a valve to valve seat leak. The red trace displays this. Jim Morton teaches this in the presentation posted above. The horizontal line represents Spark duration. That being said if you split that line in half. Every bump and wiggle to the left is caused by an external condition. Bad plug, wire, coil issue. Every bump wiggle to the right of the middle…

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Joe Diagnostician
Jersey City, New Jersey
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youtu​.​be/TgFJVL_WsMA

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Caleb Technician
Mishawaka, Indiana
Caleb Default
 

Thanks Joe. I have started mechanical testing this morning. I do have a Nicholson pulse sensor and a WPS 500 so im definitely putting them to use. Although I dont know much about secondary I know enough to say that the #2 waveform was unlike a secondary I have ever seen. I have an idea of high resistance or lean but this was way above my head haha. Thanks a lot!

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Jim Mobile Technician
Southampton, Pennsylvania
Jim Default
   

GREAT explanation, Joe. When I'm down in Florida for the Florida Foundation Training event, I'll bring you along incase I lose my voice. Watching very carefully where the Spark KV begins it's path along the Burn Time is the secret. When I downloaded the file, you can see that most times, specially when Power Braking the Firing KV is very high, all of that "NOISE" is the combustion chamber TRYING…

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Jim Mobile Technician
Southampton, Pennsylvania
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I also encourage anyone that wants to expand their knowledge on Ignition and combustion chamber operation to watch my Good Friend Mac Vandenbrink's videos. That man has forgetting more then I'll ever know.

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Andres Diagnostician
North Lauderdale, Florida
Andres Default
   

Actually 2 days ago I had a Car with misfire #3 under heavy load. The car came in with new coils and had old champion plugs that I switched out for good ones. Still misfire under heavy load! I checked secondary on all 4 cylinders and found my #3 looking like your #2. I thought it might of been carbon build up (GDI engine) so I pulled the intake and found no carbon... Switched the injectors(3 and…

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Darren Mechanic
West Allis, Wisconsin
Darren Default
 

Believe it or not I have had faulty sp plugs give me that waveform....

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Caleb Technician
Mishawaka, Indiana
Caleb Update
 

Hey guys her is a capture with Nicholson sensor in exhaust during power brake/ misfire event. diag​.​net/file/f4isrl6rh… ​ Here is a cranking capture diag​.​net/file/f4523moor… ​ Ive also added both Pico Files. Cyl#1 is always the sync. I will try to post some more soon. Thanks.

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Joe Diagnostician
Jersey City, New Jersey
Joe Default
 

Caleb this looks really cool. The Nicholson sensor is the gold trace and that represents the exhaust pulse. The red trace is the intake pulses ? When you power braked the exhaust valve did not seal and that's why the pulse raised irregular. Is that correct I am learning with this waveform analysis technique also.

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Joe Owner/Technician
Benicia, California
Joe Default
 

That was my assumption. I just received my nicholson pulse sensor so I’m eager to learn if this is correct

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Jj Technician
Quincy, Massachusetts
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Could that also be why it's so low on the cyl. 2 intake stroke? Exhaust valve open during intake? I'm super new to this type of diagnosis, still working in getting the pieces together to build a pulse sensor. Edit: Weak/broken spring maybe?

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Stephen Technician
Gallatin, Tennessee
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I have edited this post. On re-read I found that i had mis-read the capture with the exhaust waveform capture and my post had several errors. I apologize for error(s). I think that the following is correct. The exhaust pulse for cyl 2 looks normal to me. I see that the exhaust pulse for #3 is missing. The exhaust pulse for #3 is located just after the ign(C-P of the graph) of #5. Notice that…

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Jj Technician
Quincy, Massachusetts
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I see it now, I was misreading the graph. So basically the exhaust stroke ends and the actual exhaust pulse takes time to make it to the sensor? In that same capture, is the small hump in between the cyl. 3 and 4 pulses of any concern?

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Stephen Technician
Gallatin, Tennessee
Stephen Default
 

Thanks for making me re-evaluate the capture. I see that I have given you incorrect information. The exhaust pulse, for a cylinder of interest, is found to the left, not as I stated earlier, to the right of the ign/tdc of the companion cylinder. I initially wrote it that way, then changed it because that didn’t line up with #2 being the bad cylinder, which is the stated bad cylinder by CM. In…

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Ray Diagnostician
North York, Ontario
Ray Default
   

Caleb, in your first capture with the transducer in the exhaust, during the brake torque, any misfire, in 1 or more cylinders, will cause the erratic exhaust pulses. In your cranking capture, the relative compression, the intake and the exhaust stroke pulses for each cylinder look perfect. For the misfire in cylinder 2, I would concentrate on a bad spark plug or a carbon track in the plug…

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Scott Owner
Moreno Valley, California
Scott Default
 

Hi Caleb, I agree it looks like there is a mechanical/valve sealing issue - turbulence, but... Here's a few pictures of a 1988 Corvette that had a misfire on cylinders 1 & 5, similar pattern and it was caused by the spark plugs. It surprised me and looking at the plugs, they were correct for the vehicle and I saw nothing that would have caused this. They looked like they were recently…

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Joe Diagnostician
Jersey City, New Jersey
Joe Default
 

Hey Scott, I notice the hash immediately at the spark Kv point. Suggesting the problem is outside the combustion chamber. I am not sure if it looks that way because of the zoom level of the waveform.

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Scott Owner
Moreno Valley, California
Scott Default
 

Hi Joe, There's probably a few things going on here. This machine is circa 1991, CRT screen - it's a Snap-on Counselor II, that Snap-on doesn't support anymore. I'd have to dust off the manual to see what the sample rate is, but it's probably pretty low. There's some memory chips that need to be replaced, the lead set was repaired by me and actually needs to be replaced, but is unobtanium. With…

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Joe Diagnostician
Jersey City, New Jersey
Joe Default
 

I appreciate the file you shared Scott. Thanks again

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Richard Technician
Stony Brook, New York
Richard Default
 

I think you have a faulty plug or boot. You capture with the relative compression and the FLS in the intake looks really good to me. I would think that capture would rule out mechanical. Nice job collecting all the captures.

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Richard Technician
Stony Brook, New York
Richard Default
 

I was just looking through your original file and noticed that the miss does not seem to be present at idle. This would further indicate a plug or boot issue to me. I usually see mechanical issues at idle, because the sealing has to happen at lower rpms. Misses that come and go can usually be found in the ignition or rarely the fuel injection. At least that is the way I always seem to experience…

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Randy Diagnostician
Glendora, California
Randy Default
 

So richard if you had plug boot or plug bad why does your kv voltage not change in the first part of your firing line . If you had a shorted boot or plug you would expect to see kv voltage low . Read jim mortins post on kv line out putt

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Randy Diagnostician
Glendora, California
Randy Default
 

This was my scan tool 40 plus years ago

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Richard Technician
Stony Brook, New York
Richard Default
 

I like it! Its so futuristic. :) I have heard that those Sun units were very expensive at the time. I never had a chance to use one. I would imagine it stayed in one particular spot as opposed to dragging it around the shop? I honestly don't know how you guys worked on those 80's and early 90's cars. I see some cars with 10 miles of vacuum hoses and a carb, I shudder in fear. I never would have…

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Jim Mobile Technician
Southampton, Pennsylvania
Jim Default
 

Those Sun Scopes and the Allen Smart scope could easily cost $40 to $60K when they were loaded up. Myself and a lot of others mounted it up on an "I" beam which made it easier to move around in front of the vehicles. Most of the ones I had where in the front of the vehicle that I had on the Clayton Water Brake Dyno I had. I also worked for Sun Ele. and went out to the shops after the purchase to…

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Scott Owner
Moreno Valley, California
Scott Default
 

Jim, Back in the early 80's a shop I worked at was sold the Sun Interrogator. Management loved it - "Well after a battery of tests the 'machine' said you need - XYZ, ZYX, RST, TSR..." I found it pretty much useless for a few reasons. It took awhile to hook up all the leads and run through the tests and then to narrow down what was the source of the high voltage required on cylinder 4 required…

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Jim Mobile Technician
Southampton, Pennsylvania
Jim Default
 

Scott, I agree with you, I started with Sun before the Interrogator and the Investigator units came out. When I went out to teach how to use those units, I tried to get a feel for the techs ability as fast as I could. If I thought they could handle it, I would show them how to perform those automatic test, Then I would take them into the basic testing without the machine doing the test. There…

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Jim Mobile Technician
Southampton, Pennsylvania
Jim Default
 

That Interrogator is NOT mine, I just saw it in a corner of a garage and took the picture.

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Richard Technician
Stony Brook, New York
Richard Default
 

That's crazy how expensive they were. Especially when you consider the times, I think you could probably buy a small house for that price. I suppose we are all spoiled today with the newer scopes and scan tools. The ability to zoom in and capture the data. I have seen screen shots with those older scopes and I cant make out anything. Scopes now can save so much more and the cost has dropped…

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Randy Diagnostician
Glendora, California
Randy Default
   

Richard those days you had a scope or not . Like today you have the right test equipment or not . You have to invest to diag . could you fix a car quickly in todays cars with out a good scan tool no . same back then. this was my first scope . my dad taught me how to use it

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Jim Mobile Technician
Southampton, Pennsylvania
Jim Default
 

Richard, A little bit of a funny story about having those scopes back then. A real good friend of mine owned the local auto parts store and asked me for a favor, he stated that is business was suffering due to the shop owners sending some of their customer's vehicles back to the dealerships because these shops were having a hard time diagnosing driveability issues ( We are talking mid 80's with…

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Ray Diagnostician
North York, Ontario
Ray Default
 

Randy, in the first post of the 2014 Chrysler Town and Country waveforms, they only show the primary coil winding turn off voltage kick. With a good Sample Interval, all of the primary coil winding turn off voltages should all measure the same, either at idle or during WOT snaps or during brake torques. But on some COPs, it is sometimes difficult to get accurate secondary winding kv voltages.

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Randy Diagnostician
Glendora, California
Randy Default
 

Ray so if in doubt pull coil and putt spark plug lead on a recheck . right

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Ray Diagnostician
North York, Ontario
Ray Default
   

Randy, you're right and I would compare the misfiring cylinder's kv with the kv on a non misfiring cylinder. The scope's sample rate has to be higher to capture the kv output, accurately! Autonerdz sells a Coil-On-plug Extension Lead set of 4, PP400 and each extension lead has the same resistance, so the kv measurements will be accurate. But you have to lubricate the inside of the plug boot…

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Randy Diagnostician
Glendora, California
Randy Default
 

Yes. i now i have a set

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Caleb Technician
Mishawaka, Indiana
Caleb Default
 

Hey Ray , can you show me how to change the sample rate??

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Dmitriy Analyst
Toronto, Ontario
Dmitriy Default
 

Caleb, Ray will provide the optimal settings, but meanwhile you can try bumping up the number of samples to be collected to 5 or 10MS. The sample rate is the number of samples divided by screen time (the latter is 5 seconds for 500ms/div timebase). You can confirm the sample rate by opening View/Properties dialog. diag​.​net/file/fv8093jtb… ​

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Ray Diagnostician
North York, Ontario
Ray Default
 

Dmitriy beat me to it.

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Richard Technician
Stony Brook, New York
Richard Default
 

I tend to agree with you, however that relative compression and FLS sensor say the engine is breathing fine. Ray pointed out that the sample rate is a bit low, and I agree. I didn't see that last night. Caleb still did a really nice job collecting the data.

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Joe Diagnostician
Jersey City, New Jersey
Joe Default
   

At the end of your investigation did the customer ok the work Caleb ?

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Caleb Technician
Mishawaka, Indiana
Caleb Update
 

Hey everyone. I will try to post the conclusion tomm. when I get some time.

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Joe Owner/Technician
Benicia, California
Joe Default
 

Any info yet? Dying to know what you find

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Stephen Technician
Gallatin, Tennessee
Stephen Default
 

In analyzing the capture with the running exhaust; I see that cyl’s 6,1&2 have relatively equal exhaust pulses. Cyl #3 exhaust pulse is very low. Cyl 4 and 5 have distorted pulses that line up with #1 firing event. So I’m wondering if #1 has a small exhaust leak. I explained my thinking in more detail, in my response to JC.

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Simon Diagnostician
Auckland, New Zealand
Simon Default
   

Hi guys, Ive been watching this post with great interest! Ive been a Pico scope user for about 12 years now and Im still learning! I believe that the comments above about an in cylinder event are correct, but one thing that concerns me is the burn time on cylinders 1 and 2 at idle. The burn time is over 2 ms when normally we should be seeing about 1-1.5 ms. Besides a potential mechanical issue…

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Brandon Diagnostician
Reading , Pennsylvania
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Simon, anything that is going to effect how the firIng lone will also effect the burn line duration . The amount of energy in a coil is finite and must dissipate as the electrical energy is converted back to magnetic energy

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Caleb Technician
Mishawaka, Indiana
Caleb Update
 

Hey guys so the outcome was kind of boring lol. So after taking the RC test with the FLS in the exhaust and the WPS in the intake it was time to go in cylinder. Not only was I trying to learn on this one but the #2 coil is under the intake so I wanted to see what I could do before pulling the intake. Anyway I grabbed an in cylinder with the WPS500 from cylinder #1 for a known good cranking and…

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Randy Diagnostician
Glendora, California
Randy Default
 

so coil or plug bad

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Caleb Technician
Mishawaka, Indiana
Caleb Default
 

The coil.

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Randy Diagnostician
Glendora, California
Randy Default
 

Of course did not see the missing bell in pattern . Good discussion

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