Stick To Your Diagnostic Game Plan!!

In this video I jumped the gun on a misfire diagnostic. I made an assumption based of pattern failures and it cost me an hours time. It doesn’t sound like much but it is frustrating to me because I hate wasting time and making assumptions that are made with out gathering data. Any how, problem solved. -Enjoy!

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  • YHYH

    Author Reply

    Great job Eric. Great video. I'm curious to know if any other misfire source malfunction (i.e. ignition coil) would have the same effect on the other cylinders, or is this problem unique to the fuel injector. It sounds like perhaps it could be an ECU software issue unique to that make/model car. I'm wondering if the ECU has the latest software update that may affect that issue. Just a thought.

  • OMG Eric O is human!

  • I'm going to apply for a job at SMA. I arrive before Mr. O., walk the lot, diagnose the cars, fill out work orders with "runs like poop", then let Mr. O do the rest. If he can do it, I can do it.

    Your skill level is truly amazing 🏆

  • Part hanger would say need engine, and it would fix it, but way to expensive

  • I'm going to have to put my scope to work, from now on. That was very enlightening Eric.
    Recently had an Acura in the shop with all the cylinders throwing misfire codes. I didn't draw that job, but those involved assumed the INTERNET fix of valve adjustment, was the way to go… I doubted it, but if it returns, most likely it will come my way.

  • So…is the moral of the story…slow is faster?

  • i believe if you do a ecm pcm reset and start it after u can see what cylinder is misfiring.pcm going loco lol

  • In a previous career, I was managing some on aircraft testing (it was a two day test). I had a well defined plan that should have worked. Near the end of day two, some of the crew was getting anxious to clean up. I let them convince me that they could start pulling some equipment unrelated to the test I was performing. All of the sudden my test went to sh!t. It turns out there was one connection that they pulled that they shouldn't have. I was pissed…. almost as pissed as the Major that scheduled two days of aircraft downtime for us to do the testing.

    Since then, I ALWAYS stick to my plan!! Some lessons come hard.

  • This is a funky Honda. They got lucky to have you to found the exact problem.

  • A JA J

    Author Reply

    As a pilot we use checklists for everything. Even the for things we have done a zillion times we whip out the checklist and usually follow it line by line

  • This is how ya got to be good. Nothing like spitting on a car an goin to lunch to comeback and see your mistake laughing at yas

  • O2 sensor loop likely make other cylinders to rich to deal with unconsumed O2 — that's where your misfire counts come in.

  • I have a pro mechanic friend…then I go to pick-a-part and get the part it needs for a few dollars.

  • Great job and so true about having a routine.

  • Problems like this make your channel worth watching

  • Could the failed Injector be drawing enough current to bring down the other injectors? Seems unlikely, but it's an idea.

  • Eric, this is a S.W.A.G., but could the shorted injector cause the injector driver in the module to act up from increased amperage due to the shorted injector ? just wondering.

  • Eric, thanks for this lesson.

  • @3:27 and I thought I was the only one who ever did the “stick the dollar bill up to the tailpipe” trick to see whether or not somethings misfiring.

  • I haven't scoped my own car yet so I haven't learned. But I remember you saying something along the lines of a misfire is counted by checking the engine speed at a certain point in time, if the ECU is not what it expects it to be, it counts a misfire. Something along those lines. Generally injectors are driven from the ECU. So It's possible that the injector going short is pulling parts of the ECU low and is making the ECU go wonky? I dunno, this is pure speculation, there's a reason I'm not a mechanic.

  • Yep stuck to what you normally do. Works for me…….happens to us all

  • Yes, Eric, after all, one of your mottos is "sometimes you need to slow down to go fast". Case and point…

  • That's the weirdest thing I've ever seen. I wonder if the one injector being shorted was pulling down the current for the rest of them and causing them to not fire correctly? But that doesn't explain why their per firing amperage didn't go up after you disconnected #1, or at least I didn't see it go up. I'm curious as to what the fuel pressure was reading during these tests.

  • I look forward to how you fixed it.

  • Sometimes rabbit holes are disguised as diagnostic funnels and we let our smarts out smart us. Nice recovery

  • Just a theory- it’s possible that a shorted injector would put too much demand on the injector driver in the ecm, which would then have increased resistance as it started to overheat from being overloaded. I saw that happen twice on Cummins engines about 7 years apart. You can bet your paycheck I remembered real quick the second time around that the computer isn’t always right. They would both misfire until you hooked up the laptop and did a cutout test. As soon as I clicked “start” on both trucks, the miss went away. Cummins said it’s because their t/s software actually forces the drivers to put out max power to all 6 injectors during the test.

  • Definately a strange one, if the ground is common to all 6 injectors the short could be affecting the firing of the other 5 when plugged in.

  • Thank you for this video, it reminds us to stick to routine, other wise we go chasing other potential problems.

  • Is the shorted injector pulling the supply voltage down when it fires ?

  • almost a pico only tool too fix this car your thoughts

  • Could the shorting injector be pulling the voltage lower for the other injectors, or if the feed to the injectors is current limited, current flowing preferentially in the shorted injector reduces that available to the others, and hence can’t open properly, causing misfires?

  • is it getting fire?
    is it getting fuel?
    is it getting air?

  • I went down a few of these rabbit trails because I didnt do my normal procedure them days was working on a 2000 4runner with the 3.4l v6 and couldn't figure out why it was missing on 3 different cylinders found out that the timing was fine and the fuel was fine spark was fine but the number 1 cylinder coil was bad causing the other cylinders to not get there spark as well so thought it was spark plugs and these Toyota have 3 coils on passenger side and 3 wires on driver side 2 of the miss fires were on 1 coil because the coil runs one wire and the spark plug connected to the coil and the 3rd was a coil that was going bad if it would have been left longer would of been 4 cylinders missing out of 6 was frustrating to say the least 19 years on factory coils isn't bad though

  • That was great!!!!!

  • Very interesting diagnostic find Eric O

  • Never seen a injector 1 cause multiply miss fires on other cylinders interesting very interesting

  • When I was in my automotive electrical class we would have to diagnose bugs that the teachers would put into the car. One team got a headlamps inoperable on what I think was a Toyota Camry from the early to mid 2000’s. They spent a solid two days trying to figure it out. They checked fuses, current draw, continuity, everything and then some. Turns out that model has a weird switch that is kinda hidden away. It’s this little push button thing. All they had to do was hit the switch and the lights worked perfectly. That team was so pissed. I thought they were going to cry.

  • Eric is terrible at making mistakes. I state I Am the king of wasting time and making mistakes. Huh he thinks hes so great! LOL
    luv ya man

  • My turn. Yea i mean this guy is just a jerk . Never liked him lol

  • I'm surprised & a bit disappointed the PCM injector drivers don't have current limiting.

    Wouldn't take much extra components & would protect against shorts.

  • Very strange that one injector would cause all of those problems.  I know what Mr. E needed.  Ms. Marie was not there to keep an eye on him!  LOL

  • The bad injector was stealing amps from other injectors remember the Gm multec. Injectors would always short out and do this we have all been down the bunny trail.

  • Is there any blasphemy in this link?

  • Is it possible that the shorted injector was causing o2 sensors to read extremely rich making the computer cut down on fuel on all injectors causing a lean misfire on all cylinders? Great video i enjoyed watching your thought process as you went through the problem!

  • Things like this are what makes automotive interesting. But in this case, that skill is the culprit.