'11 Corolla Misfire Case Study

Hey youtubers, we are discussing an unusual misfire diag that I helped a friend with. I hope you all enjoy!
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[@CartersDiagnostics]

I believe a loaded test would have shown more compression loss, due to less cylinder fill. During cranking and idle the cylinder has more time to fill, masking the issue.

[@VoltageDropDiagnostics]

I agree 100% unfortunately it wasnt a car that I was actually working on, so I didn't get a chance to get that waveform. I just wanted to share the differences that I was able to find, even just at idle.

[@michaelmack2888]

Great video and explanation of the diagnostic process. I have to admit I would have never caught such a small difference in the waveforms. Again, great job!

[@VoltageDropDiagnostics]

Thanks Mike!

[@grabovg]

🤢 on the 🦷 root canal. Great video

[@VoltageDropDiagnostics]

Thanks Gera!

[@smiles7631]

Great video and explanation of the waveforms!

[@kennethebel7726]

Crazy, I just struggled through a cylinder 1 misfire on a 2015 Corolla 1.8L (2ZR-FE) that was an intake rocker arm which fell off. Was on a junkyard engine I had just installed. Only misfired under heavy load. Great video, thanks PJ. BTW, TAS told me just to reinstall it, but I ordered a new one.

[@hightttech]

Really enjoyed the comparison and narrative. Thank you.

[@VoltageDropDiagnostics]

Thanks for watching!

[@DallasAutoDiag]

Thanks for sharing the case.

[@VoltageDropDiagnostics]

Thanks!

[@bartscave]

Great diagnosis. Always good to see another video from you PJ! Thanks.

[@VoltageDropDiagnostics]

Thanks, Bart!

[@shaffere33]

Awesome video and great find!

[@VoltageDropDiagnostics]

Thanks!

[@goodautodiagnosticsllc7475]

Awesome case study and combined effort!

[@VoltageDropDiagnostics]

Thanks Brian!

[@dtandfam8100]

Awesome explanation of in cylinder pressure analysis! Thank you for posting this!

[@VoltageDropDiagnostics]

Thanks for watching!

[@PaulOneel]

Glad to see you posting again

[@VoltageDropDiagnostics]

Thanks! Glad to be back!

[@BrianMann216]

Fantastic job 👏 well explained.

[@VoltageDropDiagnostics]

Thanks!

[@rp5029]

Great case study sir. Thank you for sharing.

[@VoltageDropDiagnostics]

Glad you enjoyed it

[@alrifainidal]

well done mate. great job i am thankful to learn from you

[@VoltageDropDiagnostics]

I appreciate that!

[@neverstoplearning382]

Another great little class. Thanks for the video. Best regards.

[@VoltageDropDiagnostics]

Thanks!

[@spot-onautomotivediagnosti7583]

Great case study! The combined efforts here are A+ Thanks for sharing.

[@VoltageDropDiagnostics]

Thanks Don!

[@jgeorges3061]

PJ, Great thought process and information was showed in this video always learning now I need to save to buy pressure trance for in cylinder test to find those hard problem as James had thanks for sharing brother.

[@kc360awareness]

Great job PJ. Glad to see you back making diag videos. Well explained and appreciated.

[@VoltageDropDiagnostics]

Thanks Kevin!

[@jamesl197999]

Great case study.

[@VoltageDropDiagnostics]

Thanks!

[@SuperMarioDiagnostics]

That is an impressive find! Truly nice work! Sure beats blind teardown 💪

[@VoltageDropDiagnostics]

Thanks Mario!

[@romanosautomotive]

Great video PJ. Good to see you back again 🤜🤛

[@VoltageDropDiagnostics]

Thanks!

[@kevincampbell8298]

Interesting difference in shape between the 2 and single intake valves.

[@VoltageDropDiagnostics]

Yeah! Not much of a change… but enough of one.

[@tylerwilliams3868]

great video love learning about these incylinder pressures. been trying to get my shop to buy one. but just having a scope IN general has been so great

[@accaautodiagnostics]

Depending on what scanner you use they can use pressure transducers in scope mode and you can do the same..

[@esmelvingomez9505]

Great video, new subscriber here. I believe this could have been found with an old school running compression test. Great job and amazing eye 😂

[@PaulysAuto]

This is a great video PJ...it's crazy how difficult it is to identify this even with the WPS. Thanks for sharing this with us!

[@VoltageDropDiagnostics]

Thanks buddy!

[@kirkabrahamson1148]

Good to see you back on the tube again PJ. Great video. In cylinder is definitely not the easiest to diag when it comes to oddball problems but as you had done by breaking it down you got to the problem. Lots of good points to take away from this especially practicing on known goods, somethin most of has have trouble doing as usually too busy trying to fix the bad 😂😂

[@VoltageDropDiagnostics]

You got that right! I only think about getting known goods when a bad is in front of me haha

[@macdonaldsmotorworks]

nicely done and I didn't find you rambly at all... I honestly like hearing your thought process as to how you determined what was up. This really illustrates though that having known good is really important, and if/when we've got a car that isn't missing that we can study (even if only for 20 minutes) it's much easier to spot problems when they come into the bay

[@VoltageDropDiagnostics]

Yeah, when I was first sent the "bad" waveform I wouldve bet a paycheck on the exhaust valve closing timing being off. It just seemed far later than most other toyotas that I have seen. This was a lesson for me on continuing to look at and study known good vehicles.

[@juansautodiagnostic6199]

Great video man.

[@VoltageDropDiagnostics]

Thanks!

[@High_Tech_Mountain]

Great captures and case study brother! I wonder what a cranking intake capture would look like as well. Thank you for sharing w/us and to that Toyota group… the proof is in the captures! 💪💪💪

[@VoltageDropDiagnostics]

Thanks Angel. I’m curious as to what you think. Do you think there would’ve been a noticeable difference in the intake waveform?

[@High_Tech_Mountain]

@@VoltageDropDiagnostics I would like to believe that you would see a difference because one of the two valves wasn’t opening. Obviously not a difference like the Chevy example. Definitely interesting case study!

[@thecardoc100]

Nice job PJ. When the next one comes along, take advantage of the Snap Throttle test and as mentioned by some of the others put a transducer in the intake and watch the vacuum pulls. With a Snap Throttle test, the faster the engine revs the less air that gets into the cylinder when only one of the valves is working and the loss of compression will really stand out.

[@HouseCallAutoRepair]

Sounds like Bernie!

[@VoltageDropDiagnostics]

I agree. Unfortunately this wasn't a car that I was working on myself so I didn't get a chance to get those waveforms. And the valve cover was already off before I had a chance to ask for them. Although if you have any waveforms from a 4 valve engine with a singular valve not opening, id love to see them to see what it would look like snap throttle.

[@thecardoc100]

@@VoltageDropDiagnostics Hi PJ. I did find a reference capture but it is in one of Bernie's classes so I can't share it here. There is a dramatic difference of course in the peak compression but you also see the cylinder pull some vacuum on the intake stroke and you don't see that on the reference cylinder capture. I also placed a link for this week's variable cam timing class online that Tim and I are doing in case anyone is interested.

[@davidwagner3356]

This was an excellent video. Just goes to show that we can't study enough waveforms to get really good at it. I can say for myself that IVC is one part of the waveform that I don't pay close enough attention to I think mainly because sometimes it's hard to see at first glance.

[@VoltageDropDiagnostics]

Yeah, I agree. I go through phases where I get really deep into in cylinder waveform analysis. But then it fades away for a few months and I need to relearn everything that I forgot when I get back into it.

[@jameswasher3938]

"No way to diagnose without a teardown"? Shut the engine off, remove the pressure transducer, insert an endoscope just barely into the cylinder and watch the valves while you bar the engine over? Of course, be careful near TDC should you happen to end up on an exhaust stroke first. Great video. Thanks

[@VoltageDropDiagnostics]

Actually, you’re right and i didn’t think of this.

[@kc360awareness]

Wow that’s a simple approach.

[@billrimmer5596]

Thanks!

[@HouseCallAutoRepair]

I became interested in cars before there was solid state... Compared to gaming, I've gone from an Atari to virtual reality, and missed everything in between... This stuff blows my mind, but it's so amazing!

[@VoltageDropDiagnostics]

It is cool to me! I love learning about this stuff.

[@thecarguy306]

Nice case study PJ. I wonder what an intake pressure waveform would uncover as well? Less of a "pull" on that cylinder? I too don't practice this stuff enough but love when I get the opportunity to.

[@VoltageDropDiagnostics]

I wish that I was able to get that waveform. Although I feel like at idle the difference wouldve been hard. And at high RPMs intake waveforms just look like a mess to me haha

[@duanedonaldson2262]

Typical valve overlap, the intake valve opens before the exhaust valve closes to help intake airflow, and gases entering the cylinder gain a little extra speed. Intake opens before TDC and exhaust valve closes after TDC, you should have these specs for each Toyota engine. Also, get used to measuring the downward slope at 380 degrees to help with bad timing issues. Thanks for the case study.

[@jeremyanthony9300]

Faye Hadley would be awesome at diagnosing this too..

[@martinezautodiag1670]

Great explanation and case. I would like to see the intake pulse with a pulse sensor, I believe it would be a lower pull on that cylinder. Thanks for sharing this.

[@VoltageDropDiagnostics]

I wish I had one to share! I wonder how much lower it would actually be.

[@jameswasher3938]

@@VoltageDropDiagnostics That would be great to have. Almost makes me want to remove a rocker from a dual intake engine to test it out.

[@CartersDiagnostics]

@@jameswasher3938 do it

[@jameswasher3938]

@@CartersDiagnostics I'm retired now so I don't have a lot of vehicles coming through the shop. Sorry.

[@Mclain555]

Great explanation. I wonder if probing the intake pulses at wot would have shed some more light at the issue. I had a case of a peugeot with variable valve lift that would start to Misfire when reaching 80 degrees C. Was able to capture the intake pulses using the OE sensor and determine it was dropping an intake seat when reaching that temp.

[@VoltageDropDiagnostics]

That’s a good question! I wish that I had an intake waveform to share!

[@danman9017]

good job

[@VoltageDropDiagnostics]

Thanks

[@SchrodingersBox]

Good presentation. Seems a bit of subjectivity to the analysis. I recently started doing in cylinder pressures and it’s hard for me to justify tear down based on minor changes like that.

[@VoltageDropDiagnostics]

Yeah, I went over and watched your recent in cylinder video showing the Brandon Steckler syringe demonstration! Solid video! I took a 8 hour class from him! A couple of times! He is pretty amazing with these techniques! Keep practicing with it. With enough experience with these testing techniques, you too can be comfortable justifying tear down because although that change seemed minor. Pressure shouldn't be increasing during the compression stroke until the intake valve close. And with experience, they'll start to stick out like a sore thumb! Hope you learned something!

[@colejensen5812]

So, what was causing the misfire? 1. The waveform indicated that the overall cylinder pressure was the same between known good and the cylinder that was misfiring. Which means similar air mass (Maybe not fuel volume though) 2. The expansion stroke indicated that cylinder volume was not lost as the pressure did not fall below atmosphere. 3. Slope of the voltage during the compression stroke is an interesting artifact to a missing rocker, but was it really the smoking gun? It seems to me that there is nothing in this waveform that would indicate why the cylinder was failing to contribute. I think we needed the snap throttle test to really understand what was going on in the cylinder. Combustion chamber air velocity? Combustion chamber swirl? Overall fuel volume(due to one less path for fuel to enter the chamber)? What were the fuel trims?

[@VoltageDropDiagnostics]

We know that the misfire happened at medium loads, not really at idle. We know that the misfire was caused by a missing rocker, most likely causing less than required air volume in the cylinder at higher RPMs. I agree, a snap throttle test would've been more conclusive, but I only have what I have. Remember, I wasn't the tech working on this vehicle. I just tried to show what I seen while observing the waveforms that were sent to me. This waveform may not have been perfect, but it was enough for me to say "look here when you get the cover off"

[@jeremyanthony9300]

Welcome back man. I have a 2012 with 92,500 miles on it. This past Sunday, I was out with my family, and when I left I went to start the car and the battery light came on. Stupidly, I drove the car about 10 miles back to my house. I got home and I hooked up my topdon battery tester and the car was only putting out 8volts . A couple hours later, my dad and I decided to drive it to the Toyota dealership and I went about a foot and the car died instantly. I had it towed to the dealership. The next , the dealership called me and said the car needed a new battery and a new alternator. I told the dealership to do the job. I picked up the car and the total bill was with diag, parts, and labor the total was $985.00 . They charged me $170 for the diag. The question I have is did I ruin the battery by driving the car 10 miles home running off only the battery? Get back and lmk. Thank you.

[@HouseCallAutoRepair]

Would be impossible to tell 'why' it was replaced, but there is no way running the battery down to a discharged state this way, is going to permanently damage a good battery. The battery however, may have already been in a less than perfect state to begin with, and may have been the reason the alternator quit.

[@kc360awareness]

I agree. Your battery probably wasn’t completely bad, but I hesitate to put a new starter or alternator up with an old battery. The dealership tech probably did you a favor in the long run by being thorough.

[@TR4G]

Great video, new sub earned easily 😊

[@VoltageDropDiagnostics]

Thanks man!

[@bnewton239]

good one

[@VoltageDropDiagnostics]

Thanks!

[@billshaughnessy3955]

Great case study! I am curious, are the cam lobe profiles different for the intake valves? I wonder if the non opening valve has greater lift.

[@VoltageDropDiagnostics]

No, I’m pretty sure they’re both the same profile.

[@alanw5879]

Hello there,, another great video. I was wondering if you happen to get in any 03-05' 2.4l in the shop, can you do a quick video to explain toyota's A/F sensors alittle more. I know they have bias voltage on both wires. If I remember correctly its 3-3.3volts. But im just trying to understand the diag process alittle better. How to identify a sensor fault vs. a sensor thats sending inaccurate data due to other issues. Toyota seems to be the more difficult ones out of the bunch to diagnose. Its easy to check for failed heater circuits and such but as for the positive and negative current variation for rich and lean conditions is somewhat confusing still. Thanks much

[@VoltageDropDiagnostics]

I have a video on that system.

[@drewbush6535]

I have a voltage question. Mazda3 head lights dim at night when I let off the gas and more so when hitting the brakes. (Manual transmission) thoughts 🤔

[@johnnigro4536]

Do you have a video explaining how you placed the waveforms on top of each so perfectly ? I struggle with that. Thanks for the great stuff

[@VoltageDropDiagnostics]

No. But Super Mario diagnostics has a video showing the process

[@crasher88]

you said compression test were done I assume that means a regular cranking compression test both wet and dry was performed. I'm curious to know what the results of a running compression test would have shown

[@alenmihelcic8267]

I have leaking gasket when is heating, colant go in cilinder and interrupt

[@VoltageDropDiagnostics]

Yeah, thats fairly typical on this engine.

[@zedxrom7867]

Misfire under light to medium load, with good compression and leak down. It takes less than 10 minutes to pull the valve cover and look for broken/cracked valve springs or any other obvious valve related problems indicated by the condition. How practical is this in real life, I don't know. Cool study anyway.

[@VoltageDropDiagnostics]

I know where you’re coming from. But if you already have a spark plug out to do a compression test, this adds zero time. Just use a pressure transducer to do your compression test instead of a gauge. Then you’re killing many birds with one stone performing this test instead.

[@hightttech]

Many vehicles are NOT so easy; rocker covers BURIED. Practice practice practice, and enjoy the easy ones.

[@CartersDiagnostics]

The experience gain is worth the extra time.

[@hoaxs1939]

Curious if this would be enough to have a caused a fluttering vaccum guage. Good case study, thank you for sharing.

[@hightttech]

Definitely would like to see delta sensor on intake and exhaust, along with in-cylinder snap-accelerate and cruise waveforms.

[@VoltageDropDiagnostics]

Thats a really good question! I wish that I knew the answer to that question.

[@gregfe6962]

grate aerodynamics lesson, another baby step to go. Apart of the mechanics the most bothers me your root treatment, analogically if you weld your engine oil plug and your never change the oil. I can tell you from my experience only is not going to end happily.

[@dimasrodriguez3155]

What is the fix?

[@VoltageDropDiagnostics]

What was the failure?

[@two6s722]

Noice!

[@VoltageDropDiagnostics]

Thanks!

[@deeznutz3494]

These “old school testing methods” you speak of wouldn’t have missed anything, that is, if the correct method was applied. You say the misfire was light/irregular at idle, then got worse as RPM increased.. So there’s no doubt the compression tested normal at cranking speed since the RPM is too low. I’m willing to bet, and I’m sure others would agree, that if you have a miss that runs up the counter at idle and can be felt, a running compression test would show lower than that of a known good cylinder. You didn’t say there was any popping noise from the engine, so If the leakage test comes up negative, and running compression is low, The next place I’m looking is intake valve lift. At this point, my diagnostic is done Scoping a compression trace may provide precise data, that I guess could prove itself to be useful for the sake of diagnosing for some.. But ultimately, the use of conventional tools, along with the proper equation, would give a more clearer picture of where to look next and would get you there more quickly, without over-analyzing data, needing known-good waveforms, or a tear down. This is a prime example of a scope being misused, and why I steer clear of using one at all costs. You just caught a fish for James by helping him here. Instead, he needs to be taught how to catch his own fish by analyzing symptoms and creating a diagnostic strategy that best suits the situation, and to use the right diagnostic tool for the given problem. Blindly looking at scope data without properly analyzing symptoms (or in other words, replacing the 6 step diagnostic procedure with a scope) can easily lead you to a dead end (and I’ve seen it happen), because in many cases nothing jumps out at you when looking at scope data, and therefore I believe this can hinder an inexperienced tech from developing a diagnostic sense. I guess there’s nothing wrong using a scope in place of a compression gauge to get your readings. But if you’re really telling me that dissecting this vast multitude of scope data is *the* way of coming to the final conclusion in this instance, I’d have to disagree

[@VoltageDropDiagnostics]

Thanks for watching!

[@bifftannen3167]

you're just mad because you cant afford a scope ! ( like me) , so , yea, im mad too !

[@alexschmidbauer3671]

What was the cause of the rocker arm falling Off ?

[@jamesjeter8539]

It’s hard to say, but in most cases, high engine rpm. More common on a manual transmission, but most automatic transmissions can be shifted manually and over-reved. The vehicle in this video is an automatic transmission. And again, it’s hard to say what exactly caused it, it’s just more likely to be from excessive engine speed.

[@richardcranium5839]

really minute difference.

[@VoltageDropDiagnostics]

yeah, without knowing the symptoms (medium load misfire) and knowing what diag was already done, there is no way I could've put a finger on that exact part of the waveform and said "this is your problem" But it takes multiple clues to lead you down a path.

[@catherinecunningham2543]

😎 P r o m o s m.