Diagnose a Misfire LIKE A BOSS (DIY vs "Pro" Mechanic!)

[@Cryptosporidium-zu2sc]

Got a cylinder 1 misfire on a 2010 challeneger v6, your videos really help me become a better technician and make sure I get the diagnosis right the first time. I'm definitely going to thoroughly test everything before just throwing plugs at it or something it's what my customer deserves. Thank you for these videos man I'm a huge fan of you work. I find the actual diagnosing part not only necessary, but extremely fun and engaging.

[@SchrodingersBox]

Thanks man!!

[@rastacloud46]

Man, I wish I lived close to this guy so I could pay him to work on my car. What a great mechanic & a cool channel.

[@balloney2175]

he didn't show where he clamped the stuff

[@tommiesuggs9126]

Me to

[@kellismith4329]

I would happily pay him to just diagnose mine with his scanner, I can do the labor if I know what to replace

[@szn4kt603]

Where are you located

[@SchrodingersBox]

Denver colorado.

[@evglern]

Matt, I greatly appreciate your gift for teaching and explaining the way things work, and how to properly diagnose problems. It’s good to know the “why” and not just the “how”. You don’t simply “shoot a parts cannon” at the problem. Your time and effort to provide information on this channel is exemplary. Thank you for all you do!

[@shermangarvin8804]

Qpa

[@JuanPedro-vy3hw]

Great teacher

[@spelunkerd]

Thanks for the shoutout, Matt. You showed another quality diagnostic video, what we're all looking for. The lean pattern jumped out with a snap throttle, great case.

[@esemando]

0+0

[@netocdmx9736]

I have a misfire on #3 Mecanico replace spark plugs and coils; and nothing changed, I took the car to my house and this was a great profesional information.!! Thank you , you have your self a new follower.! I’m going to check injectors next…😀

[@Kaunas-rx3qv]

Another great example of how science wins the day and clearly shown through your methodology. It was nice to see your dedication to the two channels at the beginning; a thoughtful touch. I’ll be sure to follow the links to their sites. Many thanks Matt.

[@SuperMarioDiagnostics]

I, for one, very much enjoy scope based diagnostics, which i appreciate you doing matt. It covers everything, you can see the coil operating well, the oscillations at the beginning of the dwell segment and also at the end of the firing line. And the importance of establishing a baseline. Those are absolutely fundamental to secondary ignition waveform diagnosis. Keep em coming, great stuff. Maybe you'll indulge us to more scope based diagnostics, current ramping, primary and secondary waveform diagnostics, and maybe even in cylinder transducer compression waveform for those mechanical issues. It's be inferesting to see more of your take on these approaches.

[@SchrodingersBox]

Couldn’t agree more man! My original thinking of “most of my viewers don’t own a scope so i wont use it” was flawed. The scope is actually one of then best training tools because you can “see” the behavior of the voltage and amperage and how they are related to resistance variables. Yes i will be using it more, but mostly to explain principles.

[@SuperMarioDiagnostics]

Looking forward to it!

[@arthurgiannakis2156]

Loved this video. Great method of diagnosis by process of elimination and logical reasoning. Brilliantly done. I don't think anyone should have to pay a professional who's method of diagnosis is throwing parts at the problem and hoping. Anyone can do that. You pay a pro because they have the equipment but more importantly the skills and brainpower to identify and the positively isolate the problem first time. That's their trade after all. If a pro replaced 4 spark plugs and all the wires and the car is still mis-firing, why should they be paid? Mechanics are hella expensive.

[@SchrodingersBox]

Absolutely agreed!!! Thats exactly why I made this channel, so people could have an option!

[@juantaloupe71]

This is the type of professional work people need at shops. Great video thank you!!!

[@SteveRobReviews]

Nicely done Matt . Two terrific mentions and congrats on 100K , you have put in lots of hard work and have had lots of fun along the way too . Cheers 👍👍

[@SchrodingersBox]

Thanks my friend! Good to hear from you again!

[@seanzabala2401]

Great info here! I learned a lot from this guy, so whenever possible, i watch the ads to at least give back to this helpful friend.

[@lonniepersinger4676]

As Einstein once said "If you can't explain it to a six year old, you don't understand it yourself". Well Matt, you certainly understand what you're doing because I'm as green as it gets with auto fuel/electrical systems, and I understood everything you did. Exemplary Job!

[@SchrodingersBox]

Thanks, thats a great compliment!

[@billk5727]

Okay good one Matt! Glad to see you're excited and ready to go with the new channel.

[@joshuarivera7630]

I have a 2000 Dodge Durango with the 4.7L v8. I had a single cylinder misfire on #1. I tested the resistance on the all the ignition coils and fuel injectors as well as the voltages on the harness. Voltage was good, but i went to do a continuity test on #1 injector, it was completely dead. I had an open circuit. I suspected it as i had a check engine light for cylinder 1 fuel injector circuit. I tested it because i didn't know if it was the injector or the voltage.

[@dennisrandall9698]

In the beginning I thought I wasn’t gonna learn a thing. Yeah this dude is smart as shit. I’m impressed. Subscribed

[@arthurtamayo6522]

yEAH, What he said.

[@503dcccccccccccc]

Checking the coil that way would have saved me a trip to the part store and about an hour and a half laying comfortably across my grill and air box last night

[@Cavalier_Steve]

Fantastic video as always Matt, loved that you can see a fuel issue using the scope I didn’t know that! Cheers.

[@ozzman530]

This video was the straw that broke the camels back for me. Thought I could avoid it for years but my jaw dropped when watching this one. I went and joined the pay channel. I would love to be this fluid, dynamic and precise with auto troubleshooting.

[@SchrodingersBox]

Now you will!!

[@Infinite81023]

Brother! Gratitude, love and appreciation. Perfect example being the change we want to see.

[@SchrodingersBox]

Thank you!!

[@SteveLowe65]

Anytime I've run across a single cylinder misfire, I've always swapped coils with an adjacent cylinder to see if the misfire follows the coil or not before deciding that the coil is suspect. Learned a different, more efficient way today, thank you! Also, feel the need for an oscilloscope!

[@SchrodingersBox]

Yes i normally do that as well but in applications where the coil is below the plenum it is way better to do testing like this.

[@Verschlimmbesserung]

You're a mechanic people could trust you with their cars. Good job.

[@levibingham3048]

Thx for being yourself.. one of the genuine folks out there

[@slapsone6173]

Awesome video! This mechanic is a expert and explains things clearly !

[@marioespinoza8321]

I just want to thank you for taking the time to teach the average guy to get us to the next level

[@todayintheshopbanksy5904]

'Yeah, I meant the coil in the injector was bad'. Great video Matt, looking forward to the pay channel.

[@SchrodingersBox]

Dang actually you know what- I wonder if it’s possible that is what he meant and the owner miscommunicated it??? Oh snap lol!

[@TheRykpaalt]

COOL! All this stuff new to me. I like your confidence and explanation. A good teacher, one who know s the subject, makes teaching understandable to us tyros. Thank you.

[@MrLee20099]

Love to see you do a diagnostic on a P0300 code. Lots of mechanics seem to just throw parts when they see that one. Cheers

[@SchrodingersBox]

I have probably a dozen videos on P0300. One of my favorites is the Jeep - I forget title of the video but searching jeep and P0300 should find it.

[@JoaquinChea]

I have a 2014 Dodge Grand Caravan SXT in the repair shop as I’m writing this for a Cylinder 5 misfire which is not intermittent, you can feel it at idle but not so much when driving. The shop replaced the fuel injector because the ohms reading was 3.6 compared to the 3.0 on the others they suspected a bad spray pattern could be the fault. That didn’t solve the problem. Next they removed the valve cover to inspect the camshafts and lifters they claimed that this particular engine has a high failure rate. All the lifters, camshafts and springs appeared fine, they used borescope to inspect the valves and no damage was found. They reassembled and test drove the van and they say misfire disappeared after hard driving and said that indicates carbon buildup on the valves causing the misfire. They did a carbon of the van with a “BG” product. They test drove the van and said all was good. I picked up the van and after just about two miles the check engine lamp came on and I stopped the van and plugged in my basic check engine tool and it had the same P0305 code! Now the shop is telling me that the cylinder head may be bad and needs to be sent to a machine shop for inspection and repair. I’ve lost all confidence that they can fix the root problem at this point so I need a second opinion. Do you think this cylinder head could be the problem? P.S. I forgot to mention they did a leak down test on the #5 cylinder and it passed, and said valves were sealing.

[@SchrodingersBox]

not sure what to say but before all of that, they should be able to narrow it this is a fuel, spark, or compression issue. that is the very first step. they have to determine which of these it is before proceeding. if they can’t do that, someone else needs to look at it.

[@ThunderbirdRocket]

Awesome little learning gem & excellent coaching ! I’m binge watching ! 😃 Feeding the hunger ! Thanks !!

[@SchrodingersBox]

I know the feeling lol. Enjoy!!!

[@seanbruce6268]

Love the channel. Checking the injector eliminates poor terminal tension between injector and connector, nothing like having a comeback a week later on something you were positive about.

[@SchrodingersBox]

Ah good point about the terminal connection- very true. The resistance test is not excessive after all!!

[@DylanRabier]

Great diagnosis Matt. To the point and no BS 😁 Thx! 👍

[@goat_horde]

If you find this useful please dont skip the ads so the guy gets a couple pennies atleast for the free info hes been giving to us so generously

[@tacticalresearchweapons7267]

Good evening sir just another Mastertech with my two cents good thing to tell the DY is you can pull a single injector wire off on each unit without the risk of hitting 10,000 KV from dis ignition, continue to pour each injector wire to listen for change and when you pull in injector wire with no change that is your cylinder misfire. All the basic diagnosis fuel compression injector pulse which is the grounding signal from the PCM flashing injector for on-time same thing happens for the coil I’ll call Elsa hot from the PCM they are used as a ground sink from the powertrain control module have fun guys.

[@toddcott9510]

So you could have made the same diagnosis by elimination alone. What sort of a mechanic must the first guy must have been. Another excellent video. My best from Scotland.

[@u.s.a.198]

I had the same thing. Bright light on the constant 12volt side of injector but a barely seen filament on test light for the pulse side. Thank you!

[@SchrodingersBox]

That is what would be expected. The pulsewidth in the control side is just a few milliseconds so filament doesn’t ever heat up enough to light fully.

[@bobfalfa76]

Not too bad for a DIYer, just kidding,haha!! Nice diagnosis and follow up test to prove your theory. "Professionals" take note, this is how it's done.

[@markchidester6239]

Love the shirt, only from a scientist! Oh yeah, great video too!

[@maisyray]

Thank you for this video, as i have exhausted all my other options. Because I too just throw coils and plugs to fix this in the past.

[@wyattoneable]

That was a great shout out for some exceptional channels. Now back to the video...

[@stuzman52]

Very nicely done Matt with a clear and concise explanation. And great follow through with the procedures to coincide your explanation. Very nice of you Matt to give me a shout-out as it’s very much appreciated! The very best wishes to you and your family. And of course, I hope your new website will be a great hit. There’s going to be a lot of folks with vast amounts of new knowledge!!! 😀😀👍

[@SchrodingersBox]

Can't thank you enough Terry! I hope this brings you new viewership. It's true- I learned more about electrical from you than everyone else combined!

[@stuzman52]

Schrodingers Box Always a pleasure to help Matt! Holler out if you ever need anything! 😀

[@ozzstars_cars]

Stuzman is the man with the electrical plan! Good to have great channel resources to get proper guidance and education from people that know what they are doing!

[@Ironblank1]

stuzman I wanted to make couple of questions on this video and since Matt don’t like stupid questions maybe you can help me with the following.. 1) how did he know that the current draw of the test light was not going to damage the driver? 2) how base on spike on the scope he knew there was a fuel problem? 3) do you know where I can find information on how to read a scope?

[@stuzman52]

Hi Tito and hope you're doing well! For question 1, most fuel injectors will run about one amp and most test lights are around 200mA. So the current draw of the test light is less than the current driver capability. So there is no problem in damaging the driver. For question 2, you noticed that the spark line was rising up significantly at the end when the RPM was increased. This shows that the cylinder was running out of fuel making the air-fuel mixture leaner. You also noticed that the spark line looked okay when the engine was idling. This is because the computer is able to compensate for a low fuel condition at idle. But when the engine speed is increased, the air will move much faster than the fuel. And by the time the O2 sensor sees the lean condition, the computer has to compensate. Of course with the air moving much faster, the scope is able to see this lean condition. And on question 3, it takes practice in learning to diagnose waveforms in what it's telling you. Some pretty good channels that uses a scope are here on KZbin. Two channels that comes to mind are scannerdanner and south main auto. Of course there are quite a few others out there too. So a little searching and I'm sure you'll find them. Hope that answers your questions and good luck on your knowledge of learning systems.

[@Honky_Konky_Phooey]

You always talk sense it makes you wonder how the “professionals” cope at all, keep up the good work 👍

[@SchrodingersBox]

It seems the only way to me lol! I mean- it's just so.... logical! How else can you know ANYTHING other than through logic!! Guessing pisses me off lol!

[@jimbeckettplay]

I would guess that it should... LOL BTW, great shirt, and great channel.

[@gwho]

I feel like they bs you to keep up appearances and save face.

[@PeterHernandez-lg2eh]

2006 stock sti. Po302 moved swapped plugs and ignition coils . Po302 came back. Car runs great. Did a compression and leakdown on all cylinders . Alk within specs.. could it be the injectors or a vacuum leak. Have a bidirectional scanner and smoke machine all check out . Evap system seems ok.

[@SchrodingersBox]

Could be either. I would start with a fuel trim analysis as the first step.

[@FFcossag]

Quick, pedantic note on what you said at 11:10 : You had not *yet* shown that there was an open winding. At that point in the video, it could also have been a mechanically stuck injector. It's a minor point, and it was definitely proven that the injector was *bad*, but I think it's worth noting that the tests showed up to 11:10 did not specifically prove an open coil.

[@SchrodingersBox]

Not possible because there was not 12V on the ground side of the injector when ground side control was open. Only an open winding could cause that.

[@220274mark]

My van going in on Monday. Blowing black smoke on acceleration. Misfiring like he'll when engine hot. Also sometimes won't rev when I start up. Puffs put black smoke then it seems to release.

[@shawnyd8009]

A 194 bulb with the leads pulled out makes a great noid light for injectors. Great Diag !

[@SchrodingersBox]

Yep that would also have been a perfectly good way to evaluate the circuit!! In fact that's how I normally do it, but I had a lot of requests for the testlight which is essentially the same thing (except I split it into feed and control side instead of one test across the connector like a Noid light would).

[@henrycervantezzz5566]

This dude's a genius

[@carymotter4844]

I just learned so much I think my head exploded all you need is a little product awareness logical and you rock man you just rock thank you so much

[@SimplyDiagnostics]

Nice to see you giving a shout to Terry (Stutzman) he’s one of the nicest gents on YT 👍 Steve

[@SchrodingersBox]

Indeed he is!! I learned more from him than everyone else combined.

[@fstlnj29]

Needed this today. Great video and as always thank you for doing these and walking us through this...

[@SchrodingersBox]

You are so welcome!

[@gearhead1302]

Nice video. Might want to mention though that it can be harmful to use test lights with low impedance on computer circuits. That's why I just like to use my multimeter. They do make high impedance test lights though.

[@dtnel]

Don't forget a good way to check a injector for firing is a plain old simple stethoscope. I do it from time to time just so I know what my vehicle should be sounding like.

[@Fastlife660]

Matt what if the vehicle don’t have a spark plug wire for example like the notorious 2002 expedition you worked on. How would I use the probe ?

[@SchrodingersBox]

In that case I either just use a capacitive probe or you can also rig a wire between the plug and coil and do an inductive pickup on that wire- in other words make a spark plug wire.

[@Fastlife660]

@@SchrodingersBox thanks for the quick reply

[@LearnTagalogandIlocano]

Glad I stumbled into your channel. Very informative. Been watching MISFIRE videos. My car is vibrating/shaking with a flashing service engine soon that appears and reappears when the car vibrates. Brought to a known auto shop and I was told it was a misfire. They changed the coil, test drive it, but car vibrates and service engine showed up again. They weren't able to fix the problem. I was told it could be an engine problem or an internal engine problem and was suggested to go to an engine shop. But I'm still somehow skeptical, boyfriend who is a mechanic himself doesn't think it is engine problem, but isn't here to see it himself. Now I don't know what's my next step. To go see another shop or listen to them and go to engine shop.

[@SchrodingersBox]

Misfire is one of the easiest diagnoses there is. It’s surprising a shop could not diagnose it. that’s sad. Your first step is to determine if it’s single or multi-cylinder misfire. At least was that determined? Btw don’t respond in tagalog lol.

[@LearnTagalogandIlocano]

@@SchrodingersBox Thank you for taking the time to respond. 😃 It's single misfire, since they said it may have internal damage on cylinder 3. They changed it, test drive and it vibrated and service engine showed up again. They switched the coils, and still with the misfire. So they took of the new coil they put and returned back the coil that's in there. I asked if the other parts that can also possibly cause the misfire were still good or if they were checked, air system, plug wires, injector, spark plug, etc and was told yes, that's why they think it's internal damage. And that's that, it wasn't fixed and was recommended to go to an engine shop.

[@SchrodingersBox]

Ok assuming they did all those checks correctly (I’m not so sure), mechanical failure would indeed be more likely but not conclusive. It’s ridiculously easy to check. They can do either a compression test or a leakdown test. Either of these tests would confirm the misfire is due to a serious mechanical failure. The leakdown test would actually specify exactly what that failure is (head gasket, rings, valves etc). It’s just really hard for me to conceive they tested all those systems and yet they didn’t do a much simpler test to confirm it’s mechanical. That’s weird to me. It’s also possible however that you have something as simple as a vacuum leak in the intake manifold- causing an air leak or even coolant to enter the #3 cylinder and make it misfire. Did they check for that? I bet not. Wish I could look at it!

[@LearnTagalogandIlocano]

@@SchrodingersBox And I wish we're in the same city. No, they didn't mention about those tests and I didn't know either to ask if they did it. I wonder what they would have done if I've known about it and they didn't perform those. I think I'll look for other repair shops around before considering an engine shop or other options. 😕 Thank you for your time. God bless you. 🙏

[@LearnTagalogandIlocano]

@@SchrodingersBox No they didn't mention either about if they checked the intake manifold.

[@davidkelp9444]

Much better video than last time. I'm glad you got rid of it. This is more like you. Thanks.

[@SchrodingersBox]

I loved that last video! It was hilarious!

[@davidkelp9444]

I know you had fun with it and you always have intelligent replies to the haters. It just wasn't why I signed on to your channel and recommend to others.

[@SchrodingersBox]

Understood bro. Actually my advertisers felt the same way apparently as they let me have it and threatened to pull back from the channel so I definitely had to remove it lol.

[@djmv2002]

Awesome channel keeps what learned fresh and picking up new knowledge.

[@geraldmartin3625]

I love the scientific approach. I still do not completely understand how diagnose electrical problems, but your video series has gotten me miles ahead of where I was as far as diagnostic capabilities. Is Quantum Mechanix going to be an actual website or a You Tube based channel?

[@SchrodingersBox]

ACtual website. and on it, you WILL be able to learn to diagnose electrical problems every bit as good as I do. It's all about understanding the fundamental concepts. Once you do that- you can choose any way you want to do the diagnostics based on your available tools. I could have done this with a multipler, a scope, a test light, jumper wires....

[@vap0rtranz]

that vid made me subscribe, and I don't even have a misfiring engine. superb! thanks Matt

[@SchrodingersBox]

Hahaha well if you ever run into one you’re prepared!!

[@TheDisgruntledMechanic]

That is so cool to mention those guys. Both have awesome channels. Now as Wyatt said, back to the video!

[@TheDisgruntledMechanic]

Nice job for a DIY'er! Now I am going to have to give you that $3.99/ month. Damn! BTW-- good video! Congrats on the 100,000+ subs.

[@nandor690]

APPEASE US OHH MIGHTY APPEASER!!!! 😂 Great video

[@Burning7ducks]

😂

[@zachfabbian1441]

Thank you. Great information. Learned more on this video then my AUTO CLASS

[@SchrodingersBox]

Glad it was helpful!

[@aiiceejew]

This freakin Dude is awesome. He's a trip. Featuring old school with new school applications.

[@Highway94]

I completely understood the diagnoses on the injector by touching it and not feeling that slight vibration. I also understood how the test light helped by glowing indicating that the injector was infact getting power, but what I dont understand is how the obd that you used helped you figure that out ? How was it that the pulses lead you to it being a fuel problem??

[@SchrodingersBox]

it wasn’t OBD- I directly scoped the secondary. there is a long vertical line called the firing line and right after that is a short flat line called the spark line before the waveform trails off. that spark line is how I suspected it was likely to be a fuel problem. when I increased RPM the spark line, instead of being flat, jumped up and almost matched the firing line in height. this is because fuel is electroconductive so the absence of an electro conductor increased resistance on the spark exponentially resulting in that spark line voltage increase (ohms law). That led me to suspect fuel.

[@Highway94]

@@SchrodingersBox I see! Thanks man youre really helpful!

[@ozzstars_cars]

Hey nice find there Matt. Like a boss!

[@SchrodingersBox]

Thanks Ozz, good to see you back!

[@Roudter]

It's a shame that a lot of so-called professionals have given up on trying to understand electronics fundamentals....Ground (sink) switching.....total mind blower... Thanks...

[@timothyjones8753]

Very novice question. Does seeing a spark from the ignition coil really rule out the ignition coil? Reason for the question: My in-laws van had a p0300 code and the mechanic they took it to said they needed new ignition coils on all 8 cylinders. Having watched as many of your videos and soaked up as much info as I could prior to working on anything, I wanted to do some diagnosing first. I went through and checked spark and all 8 cylinders were giving spark from a good 1 - 1 1/2 inch air gap so I figured that ruled it out. My uncle-in-law (who is a mechanic and a racer) said that that test doesn't really rule it out though because it's not under load. His reasoning was that in open air it can spark a lot easier than it can under the pressure from compression and that the only way to really rule it out would be to hook a scope to it and test them that way. This being the first time I've ever tried to diagnose something like this, I left it up to my in-laws who said replace them. I wasn't surprised when the light came back on the next day. Electrical is not my strong suit (I'm Chem E not EE), is that true, even if there's spark, it doesn't rule out the coils?

[@SchrodingersBox]

An open air gap of 1-1/2 inches requires more than enough voltage to safely say the coil is not faulty. Remember in a compressed you also have gas which is electroconductive- a capacitance not available with air gap.

[@Shas4Ever]

Today is the first video I saw, and right away I have subscribed your channel.

[@davidweum9334]

Beyond my skill set. No scanner cant follow

[@SchrodingersBox]

Watch some of my "diagnosis and understanding" training videos first then re-watch and you will understand

[@chevyss18]

I only get misfire code in high rpm on cylinder 6 , also a tapping noise on full throttle , took out spark plugs and they had a little oil on threads

[@SchrodingersBox]

did you get any data?

[@chevyss18]

@@SchrodingersBox p0300 on cylinder 6 light starts flashing on full throttle then goes away in a min , checked coils good checked fuel injectors and good ,,,I’m thinking lifters 😔or valve

[@macknumber9]

I have mode 6 data that gives me misfires but not that many and they are random....I have seen every cylinder give me misfires at different times. I am chasing a mild slight shake felt at idle in the driver seat/floorpan....I hooked up vaccum gauge and pull 22 inches at idle and the needle is sitting still no fluctuation at all....I have replaced ignition coil plugs and wires (I know be easy on me I don't have the money yet for an oscilloscope and I want to learn how to do these things anyway....although the coil one tower was definitely giving me a much weaker spark then all the rest and the coil was aftermarket that was on).... Only thing left to really check is I guess compression and fuel....if this shaking is even being caused by a misfire and not a bad engine mount or harmonic balancer. The harmonic balancer does appear to move a little and definitely is original (very rusty and rubber is cracked/dry rotted)....same for engine mount I can see a very slight cracking in the rubber on one mount as well.... I guess my question is if I have good vacuum and it is stable I can probably rule out any compression issues....if it can pull good vaccuum and not fluctuate then I have good even compression no? I would think if one cylinder had weak compression it would show up as a fluctuating needle on vacuum gauge.... I either have an issue with harmonic balancer/engine mount and NO misfire or I have misfire that is causing this....I guess I would look at fuel injectors next but I just don't know how they can be intermittently causing me issues...

[@SchrodingersBox]

I would start from the very basics. start with a fuel trim analysis curved against load to get your basic starting point. right now it seems you are not eliminating variables. you have yet to rule if it’s fuel, spark or compression and are trying to look at everything. Start with the basics to get a definitive direction and stay on that path.

[@macknumber9]

@@SchrodingersBox well i forgot to mention I looked at fuel trim and I am right close to 0% on STFT and LTFT...bank 1 LTFT is around +2% and bank 2 LTFT around +6%....when I feel these shakes there is no change at all in RPM and no change at all in fuel trim.

[@SchrodingersBox]

ok that gives a great direction. I would totally start with the idea this could be engine mount/transmission mount/ harmonic balancing or other external mechanical issue first. the absence of a short term fuel trim adjustment indicates it’s less likely to be a combustion related event. if it’s not a mechanical issue, you could re-examine possibility of ignition or combustion but that isn’t evidenced right now.

[@macknumber9]

@@SchrodingersBox thank you! You are of such help always!

[@labradormcgraw]

Way to OWN the professional... like a boss!

[@waugy370z8]

99 hack job mechanics disliked this video 😆

[@SchrodingersBox]

LOL yeah its funny- as soon as I launch a video, I start getting my first dislike within a couple minutes. This means people who automatically dislike my videos actually subscribe to my channel lol!!!

[@chinodadawg8709]

this is a really good video! people like this guy are genius appreciate the video!

[@dtandfam8100]

Good work Matt! Looking forward to joining the new channel.

[@MrHC1983]

I got a hard one. Had multiple misfires, felt like a lack of power when driving up a driveway but seemed fine other then that. Decided to replace the injectors, spark plugs and coils at the same time. It was a car we'd picked up to get running for our daughter, three of the injectors got stuck in the head when swapping them out and I managed to get them out with not much effort but now I have a misfire on 4 & 6...... tried different plugs, coils and injectors. Im stumpted. I checked the wiring to the ECU and it doesn't seem to have a break in it....... so I'm tending to lean toward the head being a little off causing the injector to stay stuck open? ..... or maybe there is a vac leak around the injector maybe....... or maybe the ECU is bad?

[@SchrodingersBox]

what data do you have? I am trying to figure out why you would replace plugs, coils and injectors. what data showed all of those were bad? that seems so unlikely. especially if you suspect a vacuum leak around the injectors- what data is indicating this is a possibility?

[@MrHC1983]

@@SchrodingersBox I have a Tech2/VCM Gear. So I originally had multiple misfires on 1,2,3,4 cylinders originally. A plug change didn't fix it. To save time as it was around 200,000km's I decided just to go injectors, plugs and coils figuring it wasn't too big of a deal and it should fix it. Initially it just had the misfire, we checked the oil cap, watched the coolant to check for a head gasket issue, no problem there. The fuel rail pressure seemed fine, the O2's now atleast weirdly report one side lean, one side rich. The spark plugs vary.... under the rocket covers is clean, there was petrol in the oil which had been overfilled by the previous owner when we did the initial drain/service. At the moment I'm stuck for idea's.... other then to try and clean the carbon build up off the lifters, maybe wind the engine around and watch they all move up and down in each of the cyclinders to rule out a value issue, swap out the injectors again for the two problem cylinders, look down the 2 main problematic injector holes with a drain camera to check for any issue and to try and rtv seal the tops of them as I refit.... maybe rtv the intake instead of using the factory gasket even tho it looks OK..... outside that I guess a compression test. The weird thing is I had no misfire on 6 at all before I did all the work and only the smallest amount on 4. Now they are the mains....

[@SchrodingersBox]

Well unfortunately none of that helps but if you have a tech 2 scantool- holy hell that’s awesome! how easy is that! What’s the injector ground side switching modulation showing and have you correlated cam and crank signals? What’s the total trim curved against load while running? That will give you a basic beginning direction to go on.

[@aminmombini6882]

Thanks ,i really appriciate you for such a simple and practical test and diagnostic method, Just i 've been confuding when you're using the scope,i mean ,i don't know how to set up the scope and trigger to catch the wave form ,do me a favor with introducing a good surce to find out all the secret about how using the scope. best wishes.

[@adamburgins441]

Great video. I'm currently searching a misfire on my 90 GT Safari. Brand new engine one year old. Lots of new things also like water pump yada yada yada. I'm almost positive out of laughs that it's being just almost exactly the day of a year of the repairs that something failed because it had a year warranty😅😅😅

[@SchrodingersBox]

If it was under warranty they should fix it. Or better yet just determine the cause of the misfire and tell them what it needs

[@sanctealphonse4510]

Part two should be you calling the Craigslist serial mechanic and confronting him. LOL

[@SchrodingersBox]

Hahahaha. I actually have a previous video on a low power complaint on I think it was a Ford Taurus where the mobile mechanic who misdiagnosed it DID show up while I was diagnosing the car!!! It's a great story!

[@sanctealphonse4510]

LOL, I'll have to try to find that video...sounds fun!

[@TheFlyingJerzey]

I like the dedication and commitment to your beginning community. Subd outta respect. Keep it 💯 👊

[@simelanem]

I have exactly the same problem with one of my cars, I have changed the plugs and plug cords, the coil pack works fine. I suspected the injector in the number 1 cylinder. Now I’m going to do the power test on it and possible replace all the injectors of its indeed the injector that’s faulty

[@SchrodingersBox]

why would you replace all of them if just one injector is faulty? actually- why do you suspect injector in the first place. what evidence are you basing that it is an injector problem?

[@simelanem]

@@SchrodingersBox I checked the spark, I changed plugs, check the fuel supply. Everything is working as it should. I checked the diagnostic code and it came back with 3 codes one of them was P0261. I have since removed the injector rail. I’m sending it to someone who can do a test to confirm if it’s really gone bad. If they confirm that injector 1 is bad I’m changing all for peace of mind

[@SchrodingersBox]

when you say you checked fuel supply I assume you mean pressure. what was the fuel pressure?

[@simelanem]

@@SchrodingersBox Nope I didn’t check the fuel pressure, the car is running but misfiring. I check for spark and it was present, I replaced the spark plugs, but the misfire was still not solved. I checked the fuel injectors, when I disconnected power to the one in the first cylinder the engine still ran with the misfire but if I disconnected anymore of the other injectors the engine would cut off. Connected my cheap ODB2 scanner - trial software on pc. It showed 3 codes. One of them specifically pounded to the cylinder 1 injector. I then used a test light to check for power on all the injectors and they all had power. Didn’t check for compression - don’t have the tool yet, also I’m hoping it’s not that😂

[@greygoosemafia]

THEY'RE BOTH GREAT CHANNELS.

[@nickwilson1476]

Great shoutout at the begining. Dave has some excellent videos, I wish he made more of them.

[@SchrodingersBox]

Yes he does. and damn the quality of the video and audio kick your ass don’t they! It’s like blu-ray quality lol!!

[@nickwilson1476]

Will you be producing any literature for the paid channel that follows the instruction? .........Since, you know, you don't have another full-time job or anything. I'm excited for Quantum Mekanix to go live!!

[@SchrodingersBox]

Thinking about it!

[@InsideOfMyOwnMind]

The lean condition was apparent on this one even without the throttle snap. The snap showed it even more but yeah this was an extreme case. Nice job.

[@SchrodingersBox]

Where was it apparent without the increased RPM?

[@Freezinggreece2]

​@SchrodingersBox gotta love when a know it all comes in, says something is apparent, and dips without explaining their reasoning 😂

[@SchrodingersBox]

Hahahaha. That describes half the comments I get lol.

[@robmut1357]

Great example of using all your senses to troubleshoot. They can all come in handy. Well, except maybe for taste.

[@TheCowgirlNiamh]

Fantastic as always Matt!

[@adventures223]

Man you are a smart guy this stuff takes time to learn not easy for a beginner its a lot to remember theres got to be a faster better way than using a scope

[@SchrodingersBox]

yes it takes me several times to learn it too. what would be faster that using a scope for this though and having 100% confirmation this was a fuel issue?

[@adventures223]

@@SchrodingersBox thanks fot the reply i am learning from scanner danners engine performance diagnostics book it gets confusing because there are so many different ways

[@SchrodingersBox]

oh yeah for sure. there are many ways to do lots of this stuff. if you understand the principles though, they all make sense. it’s seeing the picture instead of “painting by numbers”.

[@russdavis1960]

Nicely done. I woulda thought corroded terminal on the distributor cap.

[@SchrodingersBox]

8-D

[@witnesszer0]

I just did a misfire diagnosis 2000 Chevy 3500 454 it was a ride along I was like miss miss miss miss, opened the hood looked at the spark plug wires grabbed a boot and my finger goes though I said well there's your problem spark plug wires turned to jelly got a new set and worked great I usually get the digi volt meter and ohm out the wires but this time I did not need it

[@cesarguardiola4045]

Awesome. Can't wait to learn more. Thank you for your work and channel.

[@SchrodingersBox]

My pleasure!

[@robertmoyer2311]

Matt, love your video. I'm stumped, 05 Chrysler Town and Country with the 3.3 has loss of power, major stumble at about 3900rpms, good wires, new spark plugs, strong spark at every cylinder, clean air filter, no restriction in the PVC, or Catalytic converter. Disconnect the spark plug wire from cylinder 4, and major stumble goes away, but still lack of power and random missing. Has good compression. Any clues??

[@SchrodingersBox]

sounds like it may be missing fuel on #4

[@robertmoyer2311]

Thanks, I guess checking out that injector is my next step. I can hear it working a stethoscope, perhaps it is leaking fuel, causing the over heating in the exhaust? Thanks for your help, any ideas are appreciated!

[@billyyoder8171]

Thank you Matt. Good job. Appreciate your videos. Bless you and your family.

[@patrickcox1951]

Hey man loved the video very thorough and very good job explaining the situation. Question I have a 2020 Ford F250 and it had a misfire on cylinder seven took it into the dealership they are telling me The engine needs to be replace. Before I took it to the dealership I replaced all the spark plugs The spark plug wire and the ignition coil on cylinder seven still having the same issue. My question to you is have you ever heard of a misfire being a symptom of a dead or dying engine especially a 2020 Ford F250. 7.3 L with 75,000 miles and proper maintenance. Thank you

[@SchrodingersBox]

All…. The… Time. Usually I diagnose that a new engine is needed when I find low compression in the cylinder and I determine it’s a bottom end issue. I would ask what specifically they found that suggests engine replacement. If it’s low compression in that cylinder then yeah, you have a major problem. If it’s anything else though, I can’t see that you need a new engine.

[@jeffarcher400]

It used to be common to take a plug wire off and hold near a ground to check for spark. I heard that this could damage modern computer controlled ignition. Is this a problem and is that grounding test light any cause for worry? My son's car has what we thought was a misfire but now not sure. It doesn't do it at idle like your example. It's a cyclical drop in power on the freeway at about 4000 rpm. Wouldn't a misfire be happening at 1000 times a minute so 100 every six seconds or 16.6 times per second. Way faster than the surge pulse. I was hoping fuel filter but when he accelerated it seems to push through it and clean up. I told him don't and we babied it home. It's an Ae86 with 20 valve and ITB. Any advice is appreciated, thanks 👍.

[@SchrodingersBox]

it makes no sense that grounding a spark plug wire with a small gap to check spark would damage the PCM. That’s what happens anyway- a spark plug is grounded to the block. Besides the voltage to the primary is the same regardless and is always ground side controlled or transistor fed. I would say the information is definitely inaccurate. as for the misfire- I would start with the basics. just curve the fuel trim against load to get a basic starting direction and go where it leads you.

[@marko_._]

What if the cylinder misfire fault code appears and disappears? I have driven months like this. Now it finally shows permanent P0303 error (it was P0304 before switching coils). The enging is shaking and there's no power to drive even at low speeds. Gonna replace the coil!

[@SchrodingersBox]

you have to collect the data when the issue is happening.

[@chevyengine307]

Your starting sound like professional 😂

[@UjazzLLC]

You're videos made me feel less stupid each time I open the hood of a car. I gota silar situation with my 03 MDX, I have a percistant cylinder #3 misfire that's causing others to also miss. I pulled and verified thet the #3 was getting sparkles, I changed the spark plugs but the miss stayed at #3 I swapped ignition coils but the Miss stays on #3 I swap fuel injector with another cylinder but the miss stayed at #3 Whath should I try next 🤔?

[@SchrodingersBox]

your next step is to test compression. if compression is good then you need to check for an intake leak.

[@robertruizcampwolfden8579]

I wonder if that fuel injector fix will fix the code for the misfire and turn off the Check engine light

[@SchrodingersBox]

Yes eventually it would. The parameters are 40 drive cycles without fault detection turns off the light and 60 clears it from pending memory. Obviously I just cleared it with a scantool to make it disappear faster.

[@TheZrpilot]

Matt, long time fan, lurker, and borderline on Quantum Mekanix. I DO really like your methods. I have the same truck, same motor. This might tip me over to being a paid sub to QM. Enjoyed your vid. Thank you!

[@SKWDMDYT]

Probably a dum question from somebody who knows little about diagnosis...why the change in the electrical signal going to the coil, if the problem is the fuel injector? Is that the ECU making an adjustment to compensate for the bad injector?

[@SchrodingersBox]

Good question. It’s because the spark line uses fuel as a conductor. without fuel, resistance across the air gap increases multiplicatively. If resistance increases, then voltage must increase as per Ohm’s Law. The “spike” on the spark line is the voltage increase.

[@HaroonKhan-qc7nm]

Nothing as a dum question. I had the same question.

[@fpatton]

Good question, I just learned, too

[@robmut1357]

But why did it only spike when you reved it? If lack of fuel made the voltage spike higher, wouldn’t it be there at all RPM’s? Great video, btw! We can see where you cut out the good details for the paid channel. Gotta smooth those transitions. Lol

[@SchrodingersBox]

Rob there are more dynamics to the resistance across the gap and I don’t pretend to know all of them but definitely the higher the compression the greater the resistance so by revving the engine, these other dynamics are introduced which in combination with the absence of fuel create exponentially higher resistance across the gap than at idle. You can actually detect many other secondary ignition issues- even spark outside the cylinder (cracked plug ceramic or frayed wire) based on the behavior of that spark line. You can even detect a low compression based on the shape of the spark line!

[@HeidiandFranny]

May I ask how you knew the ring on the scope was missing fuel? Does the fuel dapen out the signal? Thanks! f

[@SchrodingersBox]

I was able to see the increase in voltage on the spark line which would be due to lack of electroconduction in the combustion chamber. Conclusion: no fuel.

[@HeidiandFranny]

@@SchrodingersBox Gotcha! Thanks! That was great to watch :)

[@javiderek31]

My corvette ls3 has a random misfire at idle only. It revs up and down like a vacuum leak. Once warm it’ll idle normal. I changed the intake manifold gasket hoping it’ll fix it but nothing.

[@SchrodingersBox]

what evidence was there that showed it was an intake manifold gasket? I would totally start there. did you measure MAP or fuel trims?