2008 Tiburon GS with 172k Miles, Automatic Trans. Its throwing a fault code for P0448, which shouldn't be related, but who knows at this point.
The car a few weeks ago had Cylinder 2 and 3's spark plugs die on it in my works parking lot. I went ahead and swapped all four of them out and replaced the wires. Before I did that, it was terrible. It drives now.
However, a new issue popped up after the change that wasn't a thing before the change.
The car starts a little rough, it misfires in park, stopped at a red light, or stop sign as well as acceleration if I really mash my pedal down, if I'm light on the pedal, it doesn't do it so much. My first thought was an issue with spark, checked the gapping, its correct. Checked the resistance on the wires and its all fine. Sprayed a little misting of water on the wires while running to see if I could force some arcing and nothing.
I live in Clarksville, TN and theres been a lot of humidity the last few nights likely due to the nasty ass Cumberland river being so close, but I notice that if I fire my car up when there is more humidity out, it gets a bit worse. Granted, it could also just be the temperature drop from later in the day as well, but I'm not 100% sure at this point.
I've cleaned the IAC, Throttle Body, and the MAF, there hasn't been a change in the cars operation. I even swapped out the IAC and MAF with no changes as well. I busted out a meter and read the voltage of my upstream O2 Sensor, and it appears to be functioning. That being said, I hooked it up to a OBD I borrowed from O'reillys and monitored my O2 readings, and I notice when the misfires occur, there is a dip on the O2 meter from the top of the wave form, when it doesn't occur, it looks like it should, so I'm ruling out air flow. I've also done a compression test, which it passed, and there doesn't appear to be any mysterious fluids in my oil. So I'm not thinking a blown head gasket or an issue with anything inside the engine it self.
So now I'm on fuel.
Today, I noticed that on my tac, my RPMs will wobble a bit on acceleration. The only time my RPM needle moves at idle, is when it appears to miss and when it does it drops RPMs and heads back up. If the AC is turned on, the RPM drops happen more consistently, especially in Drive or Reverse. I pulled the plugs the other day to see if there was anything that could clue me into whats going down, and they're pretty clean (I mean, about three weeks old, I doubt I'd see anything on them anyway but I guess it was worth a shot?) like, nada on them. I'd almost think the engine was running lean, which it could very well be, I don't smell gas from the car. So I feel like there are periods during the misses where the engine isn't getting enough fuel.
When its going on the highway, it runs fine. That being said, if I push it up there like flooring it, It'll drop into gear for a split second, but head back into a higher one. It doesn't seem like it wants to really push RPM's that much higher than 4k. Transmission appears fine, nothing weird with it, it shifts great, so I'm feeling its dropping power when it gets into these gears and it cant sustain it very long causing it to revert back to another gear.
Oil changes have been regular, trans fluid kept up with as well. The car isn't over heating, alternator and batteries both checked and fine.
Its been pretty random as well. Used to think it started up okay on a colder start and didn't start really wigging out until higher temps, but its back to not really caring and doing it whenever. It starting alright under a colder start was after a bottle of Techron was mixed in it and I drove it 50 miles to get it flowing through the system.
I'm narrowing it down to what seems like Pump or Injectors, but I don't really have a way of figuring out which it could be and I'd like to be a bit more concrete in a diagnosing the issue since at this point, I'm tossing parts at it and praying.
Everything points to a vacuum leak.
1st, you're complaining that, "it misfires in park, stopped at a red light, or stop sign ..."
So, it's more pronounced at low rpms when engine vacuum is highest.
The real clue is, "when the misfires occur, there is a dip on the O2 meter from the top of the waveform..."
That's telling you it's running lean. If this were a fuel delivery issue, it wouldn't be more pronounced at idle when the fuel demand is at its lowest.
The wave form didn't look like the one in the image. What pointed me towards fuel is that it looks normal until the miss occurs, then it looks something like this:
Its not like the fuel curve is bottoming out when it happens, its that the fuel curve dips on a miss. That being said, i've been all over the cars vacuum lines looking for a leak, and I can't find anything. Nor can I hear anything. I've even tried soapy water and it isn't turning up anything.
Your waveform sketch shows the O2 sensor getting stuck lean momentarily.
Have you thought about your PCV valve getting hung up (stuck open) intermittently?
I suppose its possible, its not throwing a code specifically for it, but if you're saying it sounds like a vacuum leak, I know if it gets stuck it can act as one. I may yank it out and have a look, its pretty easy to get to
Can't yank it out with the tools I have, however, when I pulled the hose, it had oil in it. So I'm guessing its probably stuck open, the only thing that turns me off about the idea is my exhaust isn't smoking. Its a pretty inexpensive part, I'm going to swap it tomorrow regardless of if its good or not, it doesn't look like its ever been replaced and apparently they're supposed to be replaced every 60k or so. Bought the car used, I love used cars.
And to boot, I think my old spark plugs had oil on them. This may actually be it.
Alright, no dice. Went up and got a brand new PCV valve and hose, its still doing it. The PCV I pulled out didn't rattle like it should, but it was sealing and opening just fine. No holes in the hose, but replaced it for good measure.
Also worth mentioning, I ruled out vac leak a bit back because of a lack of audible evidence of it, and the RPMs aren't surging up nor is it Idling high. When I say its idling rough, it Idles normally, with an occasional misfire, or what SOUNDS like a misfire. When it does it, the RPM needle drops a bit and returns to normal. The RPMs feel normal. When I accelerate, if I mash the gas, the engine sounds like this:
https://www.youtube.com/watch?v=UL80srzvlL8 (The noise is around 12 seconds, ignore the rest of the video its pointless.) You can hear the engine sound like its stuttering upon accel, ignore the metal tink. Its a can of soda popping. It DOES NOT do this every time, just occasionally. Sometimes, if the conditions are right (which I have no idea yet what those are) it wont do it at all, until the engine is at Operating Temp. Then sometimes, it decides it wants to do it no matter the temp. Its hella weird.
Thanks for the video. If I've followed along right, this is more of an intermittent misfire at lower rpms than a rough idle
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Your Tiburon has a coil pack and the 2nd sentence of your original post is interesting, "The car a few weeks ago had Cylinder 2 and 3's spark plugs die on it......"
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That's interesting because you have a "wasted spark" ignition coil pack, You have 2 coils for 4 cylinders and Cylinders #s 2 & 3 share a single coil. If that coil were intermittently shorting out (internally) it would cause that intermittent misfire and explain the previous issue with the #2 and #3 spark plugs.
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If you click on the image to enlarge it, you can see the cylinder numbers are marked just below the towers.
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Cylinders 1 & 4 share one coil. Cylinders 2 & 3 share the other coil.
........... might be worth considering
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Thats exactly what it was. I had the same thought when I got off work today.
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The issue occurs the most when its moist out, or when the car is HOT. So I figured electronics aren't big fans of moisture or heat, I knew it wasn't the wires or the plugs, so the only thing left really ignition wise that could pump the symptoms I had was the coil pack.
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What initially turned me off to the idea was that it looked fine, and I wasn't throwing codes for misfires, I had to watch them live on an OBD, and they were only popping for Cylinder 3. However, after work today, a coworker lent me one of his shop OBD's that fed better live data, and when I flipped the AC on to see how bad things would get, it picked up a cylinder 2 as well as a 3 misfire. That is when it all fell into place. Drove up to Pick a part, ripped a pack off a Tiburon that had a closed hood (didn't want one that got rained on) drove home, swapped the part out, and bam. Started up and idles perfectly.
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I saw several mechanics, and gave them the same list of symptoms, I was told it was:
Compression, Fuel pump, Fuel injectors, bad alternator, bad battery, vacuum leak, IAC, dirty combustion chamber, bad fuel, the list goes on. Not a single soul said a thing about the coil pack, you are the absolute first. Reddit, New Tiburon, multiple Fort Campbell and Clarksville Mechanics, and you're the first.
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Its resolved now, live data is showing things are back to normal. O2 readings normal, Catalytic converter probably on suicide watch with all the OL driving its taken, but we're back to CL. No misses, no rough, drove it on the interstate and floored it and power is back, gas mileage is back, and all it took was $20 and an afternoon ripping something out of a junked car.
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Thank you for your suggestions, I honestly wish I saw your comment sooner.
Thanks for letting us know how you fixed the problem. It helps a lot of other people with similar issues when guys come back and let the forum know how they resolved these issues
Not a problem, I hope someone sees this down the line and it helps them. This has plagued me for weeks now and I'm thankful its over.
I would continue the diagnosis with a look st the fuels filter and the injectors. If it has a MAP sensor, I would pull it and clean it out as they get crudded up over time. Also, get a new PCV valve.
The cars version of the MAP is the MAF, its been pulled, cleaned, and I even swapped it with another just to verify if there was an issue with that specific part, no change.
The PCV should be fine. Are you referring to the CPV on the charcoal box? That should be the one for P0448, its in the works.
Is there a way to tell if the injectors are clogged? I've took a screw driver to them to listen to their clicking and they all sound correct. I haven't even bothered with the Fuel Filter and Pump yet, but the car isn't dying or experiencing issues on inclines.
The MAF sensor and the MAP sensor are two different things and serve two different functions.. The MAF sensor will be located in the air intake and the MAP sensor will be located on the valve cover. The PCV valve is connected from the valve cover to the intake manifold, not the charcoal canister. If it's a V6, it doesn't have a MAP sensor, but you didn't say what engine you had in your post.
Probably did a poor job with that bit, thats my bad. I stated 4 spark plugs were changed, but I suppose thats a bit ambiguous on my part. Its a GS, its a 4 banger.
I'll take a look at the MAP sensor for the car right now and see whats up.
There can be no quality without accuracy.
Sorry, the MAP sensor is no the intake manifold, not the valve cover.
The MAP sensor is on the intake manifold, not the valve cover. Sorry.
Its going to be a pain in the ass to get off. The top screw holding it into place comes off easily enough, the bottom screw however, is hella rusted and WILL NOT move. This is going to be a most excellent part to remove. However, judging from where it is, and that the whole area was cleaned recently as it was hella dirty, it could be adding to my issues.
LMAO its not the MAP, its my TPS.
My car DOES NOT have a MAP sensor, it has the MAF and thats it. I looked at schematic after schematic and browsed a few tiburon related web boards and this car model doesn't use one, it runs off MAF. Got confused because if you look at them from behind, they look very similar.