Random missfires, I'm at a loss. Not sure where to go now

[Zaphod9er]

TLDR: limp mode. Towed to dealer. New HPFP bank 2(left side)$1800, problem persists. Requested $2400 for all new injectors. Declined, towed home. New OEM genuine injectors installed by me. Valves cleaned, New plugs, new oil, new fuel. Problems persist.

2013 Genesis 5.0 r-spec 70k miles

We just bought the car 6 months ago and have put 4k miles on it.

Back in May the wife was out getting the kids and the car started misfiring. Motor was shaking. Told her to stop and wait. I have it towed to the dealer. The are the pros after all. They get the car and diagnose the HPFP bank 2(left side). They charged me 1800 for replacement which is fine, $900 part and $180 an hour in labor. But then they ask for $2400 for all new injectors. I decline the service and have it towed home. I'm very good mechanically and I know I can do that service myself. Towed the car home and ordered all genuine Hyundai parts. All 8 injectors, clips, bolts, gaskets, etc. Just as the shop manual requests. While I'm working I notice the valves are a bit dirty as all GDI get. So I clean them as well. New plugs, an oil change, and I even drained the tank checked for sediment and put brand new top tier premium gas back in. Car runs great for 30 seconds then starts to stutter and stall. I let it settle, try again next day, same results. Today I get ahold of a fuel pressure tester adapter and hook it up. It hits 75psi and holds solid while the car runs. Infact it ran for 3 whole minutes before it stuttered. Pressure stayed solid at 75psi. I shut the car off, came back after an hour. Still holding at 75psi. 4 hours later its down to 60. So I'm almost positive that it isn't the feeder pump or the filter. I've done resistance checks on all the coils, primary and secondary. All of them test within spec. Car is throwing 0 codes. None pending. Non stored. Only the original in permanent from the initial missifres. P0300, p0307, p0308,p0030, p0050.
I'm at a loss on where to look next. Trying to not shoot the parts cannon because puts aren't cheap for this car.
I have a picoscope 2204a and leads should I need to use it. I'm just not sure where to start looking. Could it be a bad ground somewhere? A faulty pcm?? The "glitch" just seems so damn random. It's running much better than it was. Just not solved. I sometimes almost seems like a voltage issue. Like a bad ground or loose connection somewhere but no lights flicker or anything. Some of the solenoids will make alot of noises click n clicks under the hood.
Will try to get a video uploaded too.

Thanks for any help anyone can provide.

 

[Gunkk]

What was done about the fault with the O2 sensor?

30 seconds is about the time it takes for the car to enter closed loop after a cold startup. So it's plausible a bad O2 sensor heater (and/or related circuit) might be contributing to the misfire problem.

 

[mike44138]

Misfires on cylinders 7 & 8. O2 heater issues on both sides. Agree with diagnosing the O2 sensor issue first.

Check the battery age, voltage, condition. Make sure the terminals are tight and clean. These cars hate weak batteries and I ran into a misfire issue on my 4.6 that was simply a weak battery.

You tested the coils and replaced plugs, but you could also try swapping the plugs and coils from cylinder 7 and 8 to another cylinder, reset the codes and see if the misfiring cylinders change. If so one or both coils are most likely the issue. Inspect the full length of the injector and coil harnesses for any damage. Pay close attention for damaged wires where they enter the connectors, or corroded connectors.

You probably know this, but if it's misfires affecting multiple cylinders its usually bad fuel/pressure, ignition timing (bad coil or bad PCM inputs causing poor timing), or mechanical timing. Single cylinders tend to be plugs, coils, or injectors, but 1 misfiring cylinder can induce multiples due to the inconsistent mechanical timing it creates.

GDI with heavy carbon buildup will contribute to detonation. (which you've addressed) It causes hot spots for preignition, increased cylinder compression (lowers the cylinder volume), or blocks valves from sealing. I'd be sure you really addressed the carbon build up, but it sounds like you get it.

After that you start getting into mechanical timing, but you'd usually see way more issues and codes. Not sure if the 5.0 has variable valve timing like the 4.6 but that might be worth looking at too. The VVT is driven by oil pressure, so new oil and filter probably wouldn't hurt.

Thats just some ideas. Hope it helps.

 

[Zaphod9er]

So the saga continues.....
To round put all of the potential fuel related issues I went ahead and replaced the fuel filter and pump in the tank. Made sure to get a good full charge on the battery. Drove the car for 40 minutes around my neighborhood and put about 10 miles on it. Only had a couple of 1sec incidents that felt like could be missfires. No codes. Did some runs up to 50mph back and forth down a main road. And after the third pass heading home I finally managed to get something of substance. Car stalled and stuttered and died. Limped it home and pulled some codes.

PO300, 301, 307, 305, 308.

When I got it in the garage with the engine not running, it sounded like all of the sensors everywhere were clicking and clacking rapidly. Very odd and similar to previous startup attempts. Battery voltage was reading 12.37v with a meter when I parked it.
With so many new parts, and the fact that it ran fine for a decent stretch. I'm leaning towards voltage, ground, or potential ecu. But with nothing more than a scan too and a parts cannon. I'm feeling defeated, and exhausted.

If the alternator is putting out 13.7 upwards of 14v. I just don't see how a battery can effect the operation. Isn't the car operating off the alternator at that point? Or does it rely on the battery with the alternator as supplement?

Thanks for any direction...

I haven't looked too deep at the 02's simply because there are no more 02 codes. In all other vehicles o2 issues have always come with immediate o2 codes.

Just checked battery voltage again and it's down to 12.23 after sitting for 2 hours.

 

[Gunkk]

If the alternator is putting out 13.7 upwards of 14v. I just don't see how a battery can effect the operation. Isn't the car operating off the alternator at that point? Or does it rely on the battery with the alternator as supplement?

Just checked battery voltage again and it's down to 12.23 after sitting for 2 hours.

Some of the modules on our cars are powered directly from the fuse-block that sits atop the battery, so if the battery has a small internal short and is pulling down the line voltage, you will see issues. That block can also develop hairline fractures in the bus-bars that cause all kinds of Bad_Things(TM) like the car randomly going completely dark-dash-dead-stick while driving at speed. No bueno. Loose battery terminals can too.

A good battery at rest should be 12.6 volts. So there may be an issue there. If your battery is an AGM, switch back to an OEM spec flooded cell.

But before throwing another $250 at a car battery, spend $100 on a tender/charger like a CTEK MXS 5.0 that has some on board diagnostics that can detect excessive leak rates, slow charging, etc. I have one and use it on all my cars (has modes for both flooded cell and AGM), and I've found sometimes that my short trip DD genesis cars need a topping up every few months. Sometimes a battery just needs a good charge. For $100 you will a) probably be able to know if the battery is an issue, b) charge it up if it's good, and c) get a new tool to play with

 

[Zaphod9er]

But before throwing another $250 at a car battery, spend $100 on a tender/charger like a CTEK MXS 5.0 that has some on board diagnostics that can detect excessive leak rates, slow charging, etc. I have one and use it on all my cars (has modes for both flooded cell and AGM), and I've found sometimes that my short trip DD genesis cars need a topping up every few months. Sometimes a battery just needs a good charge. For $100 you will a) probably be able to know if the battery is an issue, b) charge it up if it's good, and c) get a new tool to play with

this is the route I will likely go. Also going to continuity/resistance test as best i can all of the power and ground connections and do wiggle tests. Just have to wait for the garage to cool down. 101 in my garage. 106 outside. Not the best time to do......well .........anything. it's funny you mention the DD aspect. This is my wife's car and she goes home to school and back, rarely does the car get more than 20 minutes or 10 miles in a single drive or day for that matter.

 

[Zaphod9er]

Picked up the CTEK and charged up the battery. It got the battery up to 12.99v. I pulled it off the charger and let it rest on a bench for 3 days. After the 3 day rest it was reading 12.75v. I hooked the battery up and went for a 16 mile drive. It lasted about 55 mins. 20mph through residential areas with stop n go and frequent turns with 6 or 7 trips down a 45mph main stretch. Drove with the headlights and AC running. No problems at all other than I think I might have seen the battery light blink once, maybe twice. I was watching the road, but something on the dash caught my eye and by the time my eye looked, there was nothing there. May do the next drive with a camera filming the gauges. When I pulled into the garage while the car was still running I checked the voltage at the battery and it was reading 13.7 at idle up to 13.8 at 2k rpm.

I checked the battery voltage when the drive was over. The voltage imediatly dropped to 12.4 when i shut off the car and slowly climbed as the car went into shutdown mode. After 3 hours at rest it is reading 12.55v still attached. I plan to go on another drive tomorrow morning to see if the battery continues to drop in voltage and missfires return. I would have to think an hour drive should have been enough to bring the battery back to 12.7 again.

Is the voltage regulator built into the alternator on these cars? Wondering if the alternator has the voltage right but lacking the amps to actually charge. I may pull it and have a local shop test it.

More to come.

 

[mike44138]

Sounding more and more like the battery.

A weak alternator getting ready to go is also a possibility. Yes, the voltage regulator is part of the alternator. Usually with a weak alternator you'd get a charge light on the dash. I had to replace one because of oil leaking on it. I didn't get a charge light till the battery was nearly stone dead. I also had an issue with a rubber stopper under the hood not pushing an alarm button so the car never went fully to sleep. Just sitting in the driveway in warm standby for a day or two and the battery would be totally flat.

These cars are very power hungry and they don't react well if they're not fed. If it gives you an idea, the spec on the shop manual for my 2009 4.6 calls for 108 amps of current. I'm sure yours is even more.

Did you find a manufacturer date anywhere on the battery? I'd see how old it is and possibly take it to get tested first before spending 2 afternoons tearing things apart and then putting it back together.

 

[Zaphod9er]

7/21 manufacturers date

Edit: pulled the alternator......only took an hour but damn is it there tight.... off to have it tested.

Edit: alternator failed on the bench at Orielys.. New one in hand.

 

[Zaphod9er]

New alternator is in and car is back together. Managed to get it done while it's still only 98 in the garage. Battery is on the CTEK to top it up. I should be driving after the kids wake up from a nap in a few hours. FINGERS CROSSED!!

______________________________

Help support this site so it can continue supporting you!

 

[fourthirteen]

Great. I hope that solves your problem.

 

[Zaphod9er]

Been on a couple drives in this ridiculous 107* heat. Usually driving 12-15 miles across 20-30 minutes on 3 separate occasions. Speeds ranging from 0-70mph. Everything seems to be fine for the most part. Like 98% fine. On two occasions I noticed a hesitation that seemed like missfires. Think 2 missfires then back to normal. Both presented while at a stop at or near idle. No codes thrown. Battery is consistently reading 12.7v now that the new alternator is in, both before and after the drives. With the battery 2 years old and having been subjected to discharges and bad charging from a defective alternator, I may just change the battery to cover both major points in the electric system.

Makes.me wonder if there is still a piece of the puzzle that is intermittent and the low voltage situation amplified it. Pretty sure the only way to find the culprit will be to follow the missfire counter to see if they stay localized to any 1 cylinder or bank. Or if it will in time just fully fail. Dont quite trust the car to my wife and kids, certainly not in this heat. Going to go drive again to simulate a short visit with back to back startups and see what happens. Especially now that the car has had a good heat soak.

The saga continues.....



Edit: cylinder 1 has had 3 missfires a cording to the counter. Which isn't bad for a 10 mile/20 minute drive. I just want 0 missfires. Am I asking too much? I guess I will have to just put multiple drives and pull counts each time to build a data set.

 

[Charlie1982]

Been on a couple drives in this ridiculous 107* heat. Usually driving 12-15 miles across 20-30 minutes on 3 separate occasions. Speeds ranging from 0-70mph. Everything seems to be fine for the most part. Like 98% fine. On two occasions I noticed a hesitation that seemed like missfires. Think 2 missfires then back to normal. Both presented while at a stop at or near idle. No codes thrown. Battery is consistently reading 12.7v now that the new alternator is in, both before and after the drives. With the battery 2 years old and having been subjected to discharges and bad charging from a defective alternator, I may just change the battery to cover both major points in the electric system.

Makes.me wonder if there is still a piece of the puzzle that is intermittent and the low voltage situation amplified it. Pretty sure the only way to find the culprit will be to follow the missfire counter to see if they stay localized to any 1 cylinder or bank. Or if it will in time just fully fail. Dont quite trust the car to my wife and kids, certainly not in this heat. Going to go drive again to simulate a short visit with back to back startups and see what happens. Especially now that the car has had a good heat soak.

The saga continues.....



Edit: cylinder 1 has had 3 missfires a cording to the counter. Which isn't bad for a 10 mile/20 minute drive. I just want 0 missfires. Am I asking too much? I guess I will have to just put multiple drives and pull counts each time to build a data set.

I had begun to suspect a bad alternator, based on your previous posts, so I'm glad that helped. Also I think a new battery is a good idea, based on how many problems I've read from other people on here talking about how power-hungry this car can be.

3 misfires on a 20 minute drive is nothing to worry about, in my opinion. Think about how many thousand times each spark plug fired during that length of a drive. But, as one of the others posted above, you could try swapping coils around and see if the misfire moves to another cylinder or not.