A Closer Look At A Coil On Plug Mis-Fire

We all to often (myself included) over look opportunities to further our skills and learning. Lets take a closer look at a routine repair in the shop (bad coil swap out) and see what we can learn from it.
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--Eric O.
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Disclaimer:
Due to factors beyond the control of South Main Auto Repair, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. South Main Auto Repair assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. South Main Auto Repair recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of South Main Auto Repair, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not South Main Auto Repair.

[@mirepoixmatt1]

Love Ivan walking in and you two geeking out over wave forms. Still a great video.

[@richardbartlett4075]

You both did a fantastic job! I’m 67 and taught electrical theory and hands on at a motorcycle school in the early eighties. We did not have all the sensors and ridiculous smog applications. Retiring, I went back to motorcycle repair and high performance porting with a flowbench and do my own boring and valve grinding. But when I could not run diagnostics on a particular Harley-Davidson, I decide to get software oscilloscope for my pc. Now I’m trying to learn the use of the Hantek. Thank you both for going through the reasons and testing the component, instead of just replacing the part. Very informative, my new best “subscription”!

[@JosephKing-yw6xl]

The best explanation with details at the electrical physics level I have ever seen on UTube. These two guys are well versed in ignition diagnostics and excellent at teaching the concepts and circuitry of an ignition system. They both should be at a votech college teaching. Great team. A+ from The Professor

[@chungaleta1234]

The two of you get together and all hell breaks loose!!! The board part was a hit!!!! Genius! Do more like this.

[@andrewb2326]

Hi from Australia. My Toyota with 5vzfe had a bad misfire with unburned fuel smell. I watched this video and learned how to test the coil packs. Pulled each coil and found number 3 had half the resistance of the other 2 on the secondary side (waste spark ignition). Swapped in a spare for the old number 3 and as you would say Mr O. "bada bing bada boo" - misfire gone. New coil on order. Thank you for your channel, I am very grateful to you.

[@Klintong79]

You two should do these type videos more often together. Listening to you bounce ideas back and forth between each other really taught me a lot. Very interesting video!

[@Allazander]

Really good video! I currently have a P0300 'random misfire on multiple cylinders' in my trailblazer. The previous owner gave me a box of OEM coils, he had the same issue at some point it seems and didn't know which coil was bad so he replaced them all, the box has both the good and bad coils in it, now I can test them to see which is bad and which is good. I did do the old unplug each coil in turn at idle to see which coil(s) had no effect on idle performance and the #2 cylinder seemed to be the issue, I swapped that coil with #3, the problem followed the coil so I know the coil is the issue. If I can find a good coil in the box he gave me I'll be set without having to buy any parts. Money is really tight right now and you may have just saved me quite a bit. Thanks!

[@giovannidiiasio3357]

This is the only video I found which really let me understand how coil on plug works and how they can fail. Wonderful video indeed! Please keep doing these videos as they are unbelievably helpful. Thanks, thanks, thanks....

[@erickieffer8440]

Another great post, thank you Eric, Ivan and Hanna.

[@giuseppeverdi1253]

This has been one of my favorite S.M.A. videos! I really appreciate Eric (and guest Ivan) taking the time to explain to us how these systems work.

[@mikechiodetti6737]

Thankyou Ivan and Eric O for the "Technical Detail" with a failed coil. Great Video!

[@lawnside82]

im gettin addicted to these videos. hes like eric the car guy and scanner danner all wrapped in one.. epic!

[@trcarter80]

Thanks for thoroughly exploring and explaining everything from start to finish. Most videos leave viewers with questions unanswered. Not the case hear at all. It was beneficial having two experts explain as well.

[@textbook2o11]

This is really an exceptional video. Great combination of engineering and practical knowledge. Thanks for sharing your wisdom.

[@jordysandino6577]

Hello . I have been watching both of your all channels but individually it is so nice to see both of you together with not envy from one to another. Buenísimo 👍🏽

[@zonie1953]

The two best mechanics in one place ! What a new years gift !

[@robertdavis6708]

These two work so well together they should get engaged. Fun to watch these master minds doing their thing. JUST KIDDING GUYS, ONLY WISH I HAD A TENTH OF THE KNOWLEDE BETWEEN YOU. Great instructional.

[@stevenpelican7502]

The simple white board and visualizing the ohm readings made this highly effective training. Good Job! An example of why this works; as an aircraft mechanic F-111 at the time, I had a senior mechanic ask me an assembly process, I knew him to be an excellent mech., with 28 yrs exp. I started to explain at first, but decided it would be better retained if I took him to the book instead. He started fussing that a verbal would be fine, when I had the book open, and I noticed he wasn't paying att. I realized- he could not read. He was 60yrs old and had been doing a great job for years through visualization association retention :) Pelican

[@joelmccoin9727]

Eric O and Ivan's Auto tech school.....Excellent video, really nicely done, guys.

[@Charles_Mulberry_7977]

Ivan and Eric: The Warriors for Truth!

[@kurtkennedy5370]

I learned on a picoscope, and use it for A lot of my diagnostics. everything from blower motors, lights in the instrument cluster, is all pulse width modulated, communication issues, checking time of an engine all needs and can be done with a scope to save a ton of time and accurately diagnose a vehicle. Coming from a dealership for the past 6 years, its amazing how many people DONT use it. Nice to see it being brought out, and sharing some knowledge bombs! Keep it up!

[@throttletherapy9998]

I have viewed many videos on scope patterns and techs explaining them, but yours was undoubtedly the best in putting it in laymans terms that I can understand lab scope usage. I have been looking into a lab scope again I have used them in the past ( ie snap on vantage ) but had problems getting the right pattern, even with the help from the scope and of course diagnosng the problem wrong so I just gave up and tried other methods. My wife and I own our own repair shop been I business for 16 years. I do like the diagnostics it is what I have been doing for the last 30 years but being by myself I don't always have the opportunity to go to classes on the new and fastly changing systems of these vehicles, so thanks for the videos keep em coming!

[@CaddiDaddy]

Man you have no idea how happy this video makes me. Two techs geeking out and for also very geeky viewer to watch and enjoy. Please more geeky vids like this please.

[@insaneasylum7898]

Pretty awesome having Ivan there asking questions that we may ask. Different from most of you videos but as usual it was well worth watching. Thanks Eric O.

[@davecarlson9350]

Ivan seems like a great guy! Appreciate the mental gymnastics and you two bouncing ideas and explanations off each other. This shows how a real tech works and the brains and analytic prowess it takes to be a good one and not just a wrench turner.

[@viewfromthebilge]

Great stuff! It's cool seeing you two going through this.

[@scottfirman]

My dad told me,every year they build a car ,they make it more difficult to fix,but if you remember your basic diagnosis techniques,it doesnt matter how fancy it is,they all still work off the same basic principals. I agree with him. A test light can find more problems than any fancy computer on the market. Cars still use the basics to run,that has never changed. Granted,things have gotten more complicated,but using basic problem shooting techniques,even on the newer cars,you should be able to track down any problem.

[@johnhodgson5313]

I love it! Someone who not only finds the problem but is curious as to why! When you 2 get together there is going to be good timesThanks

[@wordey123]

Great breakdown of a diagnosis and theoretical explanations. Don't know if many automotive guys appreciate this but I sure do! Thanks!

[@johnerway7255]

Eric, great video, lots of deep info ton follow. Thanks, if you can do it, I can watch. Special thanks to Ivan, watching you two talk through the condition was super. Thanks again.

[@TileRoofsCanada]

Fantastic video, I love the dissection of the problem.

[@vacuumfreak95]

You guys are awesome. Always love when Ivan joins the fun!

[@SedatedByLife]

This is why I love watching yours and Ivan's channels. I love electrical, as much of a headache it can be, but I always learn something. I work for Chrysler and trying to move to the back and would love to have the Verus when I do. Alas, they're horribly expensive though a major asset

[@squirrelkilla7371]

As soon as Ivan pops in I got the Sanford and Son theme in my head.

[@normanwhite7182]

Great video Eric and thanks for Ivan's input as well. So interesting to see the scope patterns of the misfire as opposed to a good one, and the simple ohm test on the coil to confirm your diagnosis. Many thanks--superb.

[@johnhodgson5313]

Re: the ringing on the open circuitI haven't read all 410 comments, so this may have been covered. There is a capacitor across the switching transistor in all the electronic ignition circuits I looked at, this with the coil and its DC resistance forms an LCR circuit, so if the energy is not dissipated in the spark it will be stored in the inductance of the coil and the capacitor and will oscillate until the energy is dissipated in the resistance, so the circuit will have the ringing on the scope with an open secondary.Excellent video.

[@christheother9088]

nice description.

[@KevinJohnson-fx6wq]

Wow, that was so cool and it is true that 2 heads are better than one, at least in this case. Ivan was able to fill in really well. I especially like learning about the return voltage, albeit so small returning through the ground. It reminded me of when I made pellicles at DuPont that were basically used as dust covers to etch circuits on chips. This process was done in a clean room with this solution called nitrocellulose that was only viable when the temp was between 68 & 72 degrees and the humidity between 38 and 42. The solution was dispensed on a plate of glass spinning at a certain rate which varied depending on the specific pellicle. That was in the early 90's and we were down to only being able to have sub micron particles which was the largest gap on the chip where the circuit would still function. That process may now be obsolete with the size of the chips getting smaller and smaller. Thanks for sharing.

[@gladmarchatlein8164]

Nice demonstration guys..very educational ! I apprecited so much the drawings and explanations on the white board. Thanks for your efforts guys. Blessings for you guys ! 👍😎

[@MrLarryC11]

Excellent teaching! Thanx, guys.

[@dougtexas]

Big thumbs up! Great walk-through to explain pri:sec relationships and flow back to neg batt. And ohm check validates also. Great video.

[@craigdreisbach7975]

Another great video. I was great to attach a face to Ivan whom you sometimes mention in other videos. My favorite thing is when you say "that's your problem"..you do it with such authenticity, as if you learned it from your father when you were very young. Thank you so much for the videos.

[@Veritas_mens]

Hey there Eric, this was really great video. It was great just listening to you guys collaborating on this diagnosis. I know guys are flat out working, but you guys make a great team for these videos. Your explanations were easy to understand and informative.

[@scon2006]

Great video, you guys work well together, the questions and explainations from the other guy works very well with your teaching, definatley the way forward.

[@SouthMainAuto]

+scon2006 Thanks!

[@ssh7778]

Video looked nice and clear as I watched it. Good vid Mr. O

[@SouthMainAuto]

+steve hall It is still rendering, YT is being a bit slow today, it will be 1080P HD in a few hours I would imagine.

[@chancegeorge5583]

Great video. I really liked the white board explanation. I'm always using my white board to explain things to the wife. I'd like to see another video like this.

[@user-cm9uh6sj7n]

You guys are GREAT together Iam sitting alone with a smile on my face.. Happy New Year Eric and Ivan .

[@robhunter2435]

Very educational Thanks Ivan and Eric

[@America-ev4rk]

A conversation between two genius’s....

[@peelman1506]

I got all excited for a minute as I thought the both of you would go on about the waste spark system like in my 2000 jeep xj. The coil bar is a bit of a different animal. Great video all in all. Happy New year!.

[@mmichaeldonavon]

Eric. Great explanations from you and Ivan. Very instructive - well walked through. Having worked a great deal with 4 channel scopes, etc., it sure brought back a lot of memories. The only difference for me, was I was able to make small adjustments in order to really "clean up" a wave form, mainly amplitude and pulse width, etc. This was on an old Bendix Weather Radar, on USAF Aircraft. Its pulsed output was 65KW, and it did this 400x a second. :) Loved working on that RT! Again, super explanation by you and Ivan. You two obviously have "it together" - really well! Only comment about current flow - for me, always neg to pos. Well, there is "Hole Flow" in certain transistors - Positive Holes - love that concept. :)You are really educating me - thanks a million.

[@ericcorse]

Good video from the dynamic duo. I liked the info about grounding the coil I've never heard that.

[@coollasice4175]

*Great video. Probably the best automotive video on KZbin. More whiteboard would be awesome.*

[@Dee-hi5zj]

HEY! Having Ivan walk in to South Main during working hours is kinda like Eddie Van Halen doing a surprise visit to the Letterman Show!

[@majetoJESUS]

Very very good video!! The white board made things very clear for me. Thanks guys!!

[@toddhazell925]

A great video as usual Eric and to have Ivan pop in is a bonus. Strangely enough I was expecting some bonus footage at the end with Ivan there lol.

[@dsautorepairsdinges4367]

Love all the Rockauto magnets! Another well done video.

[@TheZrpilot]

Eric O... Older (get-r-done) Jedi Master Ivan... Younger (analytical) Jedi Master You two are fun to watch! thanks!

[@echowhiskey2411]

+Max that makes scanner danner yoda

[@TheZrpilot]

Echowhiskey​ Absolutely!

[@rplayer9969]

You two did an excellent job together. Hope to see you both do more videos together...

[@garlinwillingham7011]

HAPPY NEW YEAR! Thanks for another great video. You guys keep up the good work.

[@darrenogorman121]

Excellent work guys!!!

[@ryansauto93]

Great video Eric, I really love learning about this sort of thing. I'm not a technician and therefore have never learned about using a scope and reading waveforms but I find it very interesting. Guys like you and ScannerDanner are great teachers. I had the opportunity to meet Paul Danner this summer and he is as smart and awesome as you'd expect.

[@drvnucrzy]

I'm having a problem with my traverse and I Remember this video from a few months ago and now watching this again I'm gonna go test my coils to see if I have a problem. damn I love this channel, double thumbs up!

[@markferraro5250]

Great job Eric and Ivan. Keep me coming. Thanks

[@roadkill5333]

Hey, you guys ever listen to Click and Clack, the Tappet bros, from the N.P.R. radio show?? You remind me of those guys going back and forth about car repairs!! And being humorous, while also being informative! You two make a great team!!! Double thumbs up, if I could!!

[@SouthMainAuto]

+roadkill5333 Haha a viewer sent me an older CD of them guys, they are great :)

[@OneAuto]

LMAO Eric!!! @ 16m.44s "It comes back & punches the primary coil in the face". Nice Video guys, loving the 'Ivanostics'

[@jayreiter268]

Good explanation. This all started with radial aircraft low tension ignition. There were many "experts" then reading the patterns. Most would call out "plug, lead and coil"

[@UtahDarkHorse]

Thank you, that was super informative! And it was great to see the two of you working together. Y'all make a good team. O yeah, nice whiteboard work! 😉

[@WellsVE]

Awesome video gentlemen! Let's think about getting together for a live broadcast on this issue. When you guys were on the white board, I could tell there was a lot of brain energy being generated, my glasses were fogging up. Take care, Mark Hicks Wells Vehicle Electronics

[@daveogarf]

HI, IVAN! GREAT job!

[@BrandonF601]

This is exactly what im talking about and why i have changed my direction and approach this year. I mean, Im gonna charge the customer 1hr usually anyways or somewhere around there. Swapping the coils takes about 3 minutes out of my life and the way of life for 16 yrs now for me but knowing is what its about. Right on brother.

[@wysetech2000]

If I have to do a misfire diagnosis at work I, like you simply switch the suspect coil to another cylinder and replace the coil if the miss stays with the coil and the car is out the door but it's interesting to know the way the coil failed. Years ago we tested the primary and secondary resistance of a single coil but it's too easy now to just test the COP coil in another cylinder. Nice job guys.

[@paulcoomer8486]

Thanks for doing all that to teach us !

[@dblnessa69]

Awesome to see shop tech understanding waveforms viewed on the scope, from my servicing days of radio/tv you can call those oscillations seen on the scope "ringing".

[@ridgep551]

Great info guys! Both guys are smart!

[@jaredmance8665]

Thank you for sharing that. I learned something today. You guys are awesome.

[@SouthMainAuto]

+Jared Mance Thanks

[@shawtyel7503]

Great video on board explanation.thanks guys

[@Cavalier_Steve]

Whoa bonus SMA video having Iven in the shop! Nice video guys! Cheers!

[@emtscythe3782]

Absolutely excellent video Eric. I too have been guilty of just swapping coils. But it's was nice to poke the ol brain power and make myself think and learn more about the function and theory. I'm hoping to be able to pick up a scope soon. Keep up the good work and may the new year bring you and your wonderful family Many Blessings.

[@shaneharrison4775]

Cool work both of you and its info well used and saveing the wave forms is a good idea to help in diagnosing

[@AnhYeuEmMaiMai69]

Thanks for the new video and happy New years to you and your family....

[@buffuniballer]

I'm sorry, as one who holds an Electrical Engineering degree, I have a complaint. The switch at the bottom is OPENED when you want spark. Current flows through the primary, as your waveform describes, and then the circuit is opened. When current runs through the primary, a magnetic field is created in the coil. When that current is interrupted, the magnetic field has to go somewhere and it creates a high voltage in the secondary side. That voltage is high enough to jump the spark gap. The equation for how coils work is as follows: V = Voltage, N=Number of turns in winding. Vp*Ns = Vs*Np Because Vs/Vp = Ns/Np It's the sudden stop in the flow of current that creates the voltage and ultimately current in the secondary as the B field (magnetic field for non-physics / EE types) drops. This is why at high RPMs some coils cannot keep up as you cannot build up a sufficient B field to subsequently create the high voltage in the secondary.

[@Ebooger]

Obviously that's correct, but I thought that's the way they explained it, too, even showing that on the waveform. The lack of coil saturation dwell time, as you describe, is the high RPM limitation, that's why permance cars had dual points back in the day (one pair of contacts for make, and another pair was used for break), and why the increase in the number of actual coils in all DIS systems is such an advantage.

[@zacmurray1848]

Eric O you should do video of your tool box. Also tell us what you prefer snap on or Mac tools. Nice videos thanks for all the info!

[@joe2mercs]

A couple of points, I once checked out a coil using a VOM and was told that I should have checked out the resistance of the high voltage secondary coil using high voltage as this would more accurately reflect the natural state of its operation and possible failure mode. The second point was that a faulty coil might in turn lead to failure of the switching transistor in the ECU. Not having the resources, in the event I swapped coils and at the same time checked the resistances of the all coil windings with a standard VOM; the ECU had in fact popped its switching transistor. Great video, I feel at a disadvantage not having a scope but I guess you do what you have to do with the tools and skills available to reach the right diagnosis to effect a fix.

[@motorhead6763]

Excellent tech. I had a ford triton 5.3 in a truck same issue. I fixed using fluke ohm meter. Compared all coils found one out of spec when hot. Goofy shop charged me to change all plugs didn't stop problem. So I troubleshoot it old school. Remember physics class(I am engineer) current goes from negative to positive and collapsing electric field always induces a magnetic and collapsing magnetic field induces an electric current through flux of iron core. Cool seeing Napa coil from anywhere but China. Next snap on will make stuff there...lol..Good show! Thanks שלום

[@petemiller3534]

This video was great. Know I have seen someone who has more Rockauto car picture magnets than I. I checked out the two locker doors in the back ground.

[@SouthMainAuto]

+Pete Miller that is 1/8 of the collection haha

[@kaylamarie8309]

Great video as always! If we put you two guys in lab coats and hang a chart on the front of that truck and you might as well be two electro cardio surgeons discussing a patient. I am sure to the non initiated who do not turn wrenches it sounds exactly the same. Heck I do wrench and know what's up and it still sounds the same! Dr. Eric and Dr. Ivan lol. You guys are incredibly smart! I learn tons of stuff from you and your videos. Anyone who bitches about why getting your car fixed needs to tune in and watch the processes that take place.

[@randygudeahn7304]

Happy New Year. it was nice to chat with you and Ivan the other night. Thanks for the great vid.

[@SouthMainAuto]

+Randy Gudeahn (ProTech) Heck ya, oh and next time don't feel like you have to dress up haha

[@randygudeahn7304]

That was funny. I didn't know you guys were there.

[@cgmachanic]

I love the white board explanation!!! ex USCG mechanic

[@DanielSilva-gd5cs]

Wow! That was a very nice video. Great explanations on terms and what things should look like. I like that you are doing your thing and then you had an unexpected issue happens. It happens to many people and it can be discouraging…. I just change my spark plugs and now I can’t get the truck to idle/lose of power.

[@JeffinTD]

Old video, but still totally excellent.

[@8power0]

Graet diagnostic video , i am working on a 02 trilblazer right now with an intermittent misfire suspecting a coil and a happy new year to you all .

[@SouthMainAuto]

+8power0 uhoh.... I-6 .... might need a valve springs :)

[@laohantun7404]

Thanks mates...its really refreshed my memories. I'm from Singapore, a place cars are difficult to own, costly to own😭😭😭😭😭.

[@thunderkreider121]

Great video!!! I myself not knowing the tech part of an ignition coil with the workings of the surrounding components was lost 20 mins ago. My 2009 M3 I bought (68,000 miles) 9 months ago ran like a champ until yesterday (79,000) when I jumped on it entering the FRWY paddle shifting it down to 1st (7 speed double clutch AUTO) 7,000 RPM hitting 2nd at 8300, and dropped off the throttle at 7000 before hitting 3rd (I'm already over 80mph but it is CA) only to immediately notice I've lost power. Today on a meter it shows 6 of 8 cylinder problems. I had picked up new plugs today knowing after a little research they are over due, and now after viewing your video I believe it's very possible I blew 6 ign coils. Ouch! Thank you for the great info in layman's terms!

[@OffroadEthan]

The E90 M3 with the S65 did supersede to a new coil number in Sep 2009. I'm pretty sure from a Bosch to a Delphi. There is a SB on switching from Bosch to Delphi in almost all models

[@johnmckamy6398]

I have learned that if you gap your plugs a little tight , that it ay create the slightest of fish bite as you call them at idle that most drivers wouldn't notice . great video's

[@RedneckGarage]

Like the hat :) I had an Econoline that I fought the Coil on plug for a long time until I totaled it .... then it was no problem hahaha Can I borrow your scanner ??? LOL Nice job.

[@jmcenterprises9591]

Just came over from ETCG, subscribed here. Great vids, thanks SMA.

[@SouthMainAuto]

+J Cirafic Hey thanks!

[@robertoperezrivera5866]

A very good class keep on teaching, go bills

[@spelunkerd]

In a one week gap since your last video, I scrolled back to watch this classic one again. Brilliant review, even better after a few years. Many new COP systems don't give easy access to the secondary or to the switch side of the primary, so this is harder to analyze with modern designs. If you ever get a free moment, an update regarding how you investigate those systems (with the transistor inside the coil pack) would be helpful. Happy New Year, Eric!

[@spelunkerd]

Excellent video, I'm gonna have to find some Subaru wires. Nice to hear the dialog with Ivan.

[@gordon9042]

I was doing some of the same measurements in 1960 using an old heathkit scope.