08 Hyundai Veracruz

on this veracruz I had an engine miss, felt like typical ign type miss-bad plug or coil- the only code was a P0305. It had new plugs and a new coil on that cylinder. I could duplicate the problem with a power stall or by driving it and the miss fire counter only showed #5, an occasional miss on another cyl.
The fuel trims were good on long and short termand mass air flow performed like expected and could not find any vaccum leaks, it would make the check engine light flash when driving.
Now for the rest of the story, I am fairly new with a scope, could not get to the #5 coil so I changed the plug and coil with another cylinder, no change. found a connector for #1, 3, and 5 injector, scoped the injectors 1 at a time, all looked the same and appeared to be a good pattern I did it both ways. long story short I could not pin point a problem, changed that injector and fixed it and have no idea what I should have seen on the scope-can anyone explain it to me?? thanks for your time

I personally couldn't tell you but a skilled technician can tell by the rising slope of the injector pattern whether it is opening properly or even closing properly. I imagine if you were to scope a good injector and the bad one and superimpose them on top of each other you would see a difference.

that was my point, I scoped #1,3,and 5, they all looked the same to me, I had to miss something

You may not have 'missed' anything.

All of the waveforms could very well have looked the same. A scope can't see 'dirt' that doesn't cause an increase in resistance to the injector coil.

Hindsight is 20/20, but an injector balance test would have identified that injector as being 'different' or 'suspect' from the others. This would have been my next step after performing everything you already did.

The only other test I like to perform is a relative compression check just to ensure there are no compression, timing, issues when dealing with misfires.

You performed very good troubleshooting!

Out of curiosity, did you scope voltage and current?

I did do it both ways just did see anything weird and wanted to go ahha i see the problem, I still got to the end just wanted to see it

mobileauto wrote: I did do it both ways just did see anything weird and wanted to go ahha i see the problem, I still got to the end just wanted to see it

I read this article yesterday www.searchautoparts.com/motorage/drivabi...ent-misfire-concerns which suggests that if you monitor the downstream O2 sensor it will show rich when the misfire occurs if it's a spark problem and lean if it's a
fuel problem. It would be interesting to replicate the problem (might try that myself sometime) and see how it works.

Not trying to be a jerk, but are you sure the fuel trims were reasonable during the misfire? Because if you truly had a bad injector, I figure it should have created some kind of trim reaction. +10-20%, usually.

Otherwise, I'm with Weycraze. An injector balance test likely would have pinned this down, but I don't own one. :silly: If you're game for experimenting with your scope, I've had decent results from using a knock sensor on fuel rails to identify injectors that aren't operating. Not saying it would have shown you the problem on this car, just another tool in the box.

www.scannerdanner.com/forum/diagnostic-t...-a-knock-sensor.html

Possible that injector o ring leaking air.

Tyler, that is a fabulous idea,

I cant wait to try this on a known good vehicle for testing!

Sweet

ok guys and gals, I have an update on the hyundai, and yes I am still screwing with it. after the injector it ran well for 2 weeks, got a call that it started running bad and then died, now it was a crank no start--was convinced it lost a fuel pump, checked power at the pump and it was good, checked pressure there and it was good. at this point is started but was missing but now it was on #2. I checked the coil and it was firing and the noid light blinked on the injector, by the way, had codes P0300, P0302 and P2169 or 2189 I forgot but it was lean on bank 2 which makes sense. end of day so I came back the next day, cleared codes and started it, now it set code P0306, P0300 and P2189, looked at miss fire counter and it is counting misses on #5, curiosity got me, cleared the codes and miss is gone. unplugged #2, computer killed the injector on that cylinder, 0.0ms, but now it is counting misses on #3--now on the last restart, it was not missing, it died and is a crank no start again.
I know I have got myself way off track somewhere, cant see the forest for the trees, if someone has seen this before great but I am hoping someone can shove me in a direction to start to get a handle on this

sorry for the long post and thanks in advance

ok, I have a fix finally, wish I could tell you i figured it out with a scope and scan tool, some great testing and brain power but no that aint it...... I finally convinced myself it had to be the fuel pump, just gut feeling, was out of ideas and really frustrated, so I pulled the access cover, unplugged the pump and took it out to find

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the dam thing was full of water. I am guessing after I gave it back to her the last time it ran fine until she bought gas and here I am.
I drained the tank, replaced the pump and so far no more problems

ok, I have a fix finally, wish I could tell you i figured it out with a scope and scan tool, some great testing and brain power but no that aint it...... I finally convinced myself it had to be the fuel pump, just gut feeling, was out of ideas and really frustrated, so I pulled the access cover, unplugged the pump and took it out to find the dam thing was full of water. I am guessing after I gave it back to her the last time it ran fine until she bought gas and here I am.
I drained the tank, replaced the pump and so far no more problems