Hyundai Theta II Engine in Newer Years

[Mad_Hatter]

Originally Posted by smc733
Really glad to hear that most of you think the sound is normal, and so many have had Theta II engines last long without issue. It adds to my suspicion that the engine may just not be as tolerant to poor maintenance, and for those of us who ensure timely oil changes, the chances of an issue might be lower.

The one other issue I very occasionally (less than once a month) have, is that on a first of the day start, it will lug for 3 seconds as if it is going to stall, then the RPMs come up. Probably nothing. As far as oil burning, I've been keeping an eye on that, and I haven't lost a drop, dipstick still goes right to the second dot right up until the oil change. The dealers around here always go with 5w-30 since Hyundai revised the recommendations upwards.

I'm going to have the dealer take a look when I get my next oil change (this coming weekend), but it seems like I can rest a bit easier and just keep the car as I like it.

Is your air filter clean or dirtied up?..You have 70k on this DI engine, have you ran a system cleaner (like a Berrymans) before or even a spray intake cleaner for the valves? Really dirty, caked valves can interfere with air flow, combustion and the valve's ability to shut all the way.

You can clean them yourselves but it's more involved then just dumping a can of cleaner into the tank. You've got to introduce the cleaner via the intake. A shop can do this if you don't want to bother, but it'll cost ya a pretty coin..

Your throttle plate could be dirtied up as well. Cleaning that would be similar to the valve cleaning but a little more involved because you really should get in there with a good solvent (i use carb cleaner), toothbrush and rags. And while you're in there, check the PCV valve.

 

[wag123]

Originally Posted by smc733
I am thinking of just trading the car in for a 2016 or 2017 Camry (pre new DI engine/8spd) that I can keep until the wheels fall off. Likely an LE, but maybe an XLE, only thing I will do is that I will probably put in an aftermarket headunit so that I can keep CarPlay.
New Camrys have dual fuel injection systems, both direct and port injection, offering the advantages of both. No oil dilution or carbon build-up problems have been reported. The Aisin 8-speed automatic comes from the same transmission family as the previous 6-speed, it is fine. Durability has not been an issue (outside of early AWD V/6 applications) and should not be an issue going forward. Early shift quality complaints have been addressed with improved software. 2019 and up Camrys come standard with Apple Carplay.

 

[WhizkidTN]

FWIW: My Optima's engine, which never used oil or had ANY issues (even while tuned making lots more HP/TQ), up until it developed the "rod knock of death" at ~76K miles in Dec '18. In less than two weeks, I had a new long-block engine replacement and a life-time warranty on the engine. The new long-block has all the improved internals. They even paid for my rental and moved over all my engine mods to the new engine (except the ECU tune, which they overwrote with updated knock sensor firmware). I have been very pleased thus far and my new engine (now re-tuned) develops tons of power, as before. So, yes, I'm a happy camper and the original owner.

Stock: 274HP/269ft-lbs on 87 octane at the crank.
Now: ~350HP/310+ft-lbs on 93 octane at the crank (estimated).
Downside: Open wheel FWD (no LSD) so easy to smoke a tire but on-ramps and such are VERY fun and she sounds great!

FYI: I took some pictures of my intake valves on the old engine when they pulled it and they had plenty of gunk on them but not nearly as bad as others I've seen online. That despite running dual OCCs, OCI of 4K miles, Top Tier 93 octane gas and such so my efforts only slowed the process, not stopped it. I'm very glad the new Theta III 2.5L (and turbo) has both PFI and GDI which will resolve this concern once and for all (assuming you run gas cleaner ever so often).

 

[rekit]

Bought the wife a 2016 Optima from Hertz after reading the problems were confined to the earlier years. Was pretty PO'ed when we got the letter to update the software that looks for the rod knock. Bought this car so we would have a newer, dependable ride. (my Tacoma is reliable but it is an 01 with 240K on it) . 60K on it now and it is an amazing car. I'm doing 3500 OCI's with the Kia filters and full syn 5-30 Pennzoil. No issues yet. But living close to Houston and driving there for Dr. visits, it's gonna be hair-raising to get off the freeway if that limp-home mode kicks in. Has anyone been in that mode? How brutal is the power reduction? Around here, to get over you have to speed up, not slow down.

 

[wemay]

Type and viscosity of oil makes no difference if the vehicle has the issue. Every last one of the forum entries i've read on the Hyundai boards where a member gives background prior to their vehicle's demise has said they used top brand synthetics. Most used 5w30 (some Xw40 for turbo) and carried out meticulous maintenance.

 

[1978elcamino]

Set aside 100 bucks a month for a year and a half. If in the next 2 years something happens you have already set aside the funds for a used engine for R&R.

 

[smc733]

Originally Posted by Mad_Hatter
Originally Posted by smc733
Really glad to hear that most of you think the sound is normal, and so many have had Theta II engines last long without issue. It adds to my suspicion that the engine may just not be as tolerant to poor maintenance, and for those of us who ensure timely oil changes, the chances of an issue might be lower.

The one other issue I very occasionally (less than once a month) have, is that on a first of the day start, it will lug for 3 seconds as if it is going to stall, then the RPMs come up. Probably nothing. As far as oil burning, I've been keeping an eye on that, and I haven't lost a drop, dipstick still goes right to the second dot right up until the oil change. The dealers around here always go with 5w-30 since Hyundai revised the recommendations upwards.

I'm going to have the dealer take a look when I get my next oil change (this coming weekend), but it seems like I can rest a bit easier and just keep the car as I like it.

Is your air filter clean or dirtied up?..You have 70k on this DI engine, have you ran a system cleaner (like a Berrymans) before or even a spray intake cleaner for the valves? Really dirty, caked valves can interfere with air flow, combustion and the valve's ability to shut all the way.

You can clean them yourselves but it's more involved then just dumping a can of cleaner into the tank. You've got to introduce the cleaner via the intake. A shop can do this if you don't want to bother, but it'll cost ya a pretty coin..

Your throttle plate could be dirtied up as well. Cleaning that would be similar to the valve cleaning but a little more involved because you really should get in there with a good solvent (i use carb cleaner), toothbrush and rags. And while you're in there, check the PCV valve.

I've tried to stick to Top Tier stations as much as possible, and run either Techron or Gumout Regane before each oil change, but I realize the impact of this is limited on DI engines. Perhaps if I were to keep the car for sure, I might spring for dealer service on these items.

Originally Posted by wag123
Originally Posted by smc733
I am thinking of just trading the car in for a 2016 or 2017 Camry (pre new DI engine/8spd) that I can keep until the wheels fall off. Likely an LE, but maybe an XLE, only thing I will do is that I will probably put in an aftermarket headunit so that I can keep CarPlay.
New Camrys have dual fuel injection systems, both direct and port injection, offering the advantages of both. No oil dilution or carbon build-up problems have been reported. The Aisin 8-speed automatic comes from the same transmission family as the previous 6-speed, it is fine. Durability has not been an issue (outside of early AWD V/6 applications) and should not be an issue going forward. Early shift quality complaints have been addressed with improved software. 2019 and up Camrys come standard with Apple Carplay.

Interesting and good to know. I kind of prefer the more simple design of the last generation, but the new ones do have a number of nice upgrades on the LE compared to last gen. Maybe if I go this way, I'll test drive them.

Originally Posted by WhizkidTN
FWIW: My Optima's engine, which never used oil or had ANY issues (even while tuned making lots more HP/TQ), up until it developed the "rod knock of death" at ~76K miles in Dec '18. In less than two weeks, I had a new long-block engine replacement and a life-time warranty on the engine. The new long-block has all the improved internals. They even paid for my rental and moved over all my engine mods to the new engine (except the ECU tune, which they overwrote with updated knock sensor firmware). I have been very pleased thus far and my new engine (now re-tuned) develops tons of power, as before. So, yes, I'm a happy camper and the original owner.

Stock: 274HP/269ft-lbs on 87 octane at the crank.
Now: ~350HP/310+ft-lbs on 93 octane at the crank (estimated).
Downside: Open wheel FWD (no LSD) so easy to smoke a tire but on-ramps and such are VERY fun and she sounds great!

FYI: I took some pictures of my intake valves on the old engine when they pulled it and they had plenty of gunk on them but not nearly as bad as others I've seen online. That despite running dual OCCs, OCI of 4K miles, Top Tier 93 octane gas and such so my efforts only slowed the process, not stopped it. I'm very glad the new Theta III 2.5L (and turbo) has both PFI and GDI which will resolve this concern once and for all (assuming you run gas cleaner ever so often).

This is what has me worried, that things are good until suddenly they're not on these engines. That said... I do know that a 2011-2012 model was an almost sure failure, while there were design changes for MY '13 and again MY '15 that seem to make the issue less common.

Originally Posted by rekit
Bought the wife a 2016 Optima from Hertz after reading the problems were confined to the earlier years. Was pretty PO'ed when we got the letter to update the software that looks for the rod knock. Bought this car so we would have a newer, dependable ride. (my Tacoma is reliable but it is an 01 with 240K on it) . 60K on it now and it is an amazing car. I'm doing 3500 OCI's with the Kia filters and full syn 5-30 Pennzoil. No issues yet. But living close to Houston and driving there for Dr. visits, it's gonna be hair-raising to get off the freeway if that limp-home mode kicks in. Has anyone been in that mode? How brutal is the power reduction? Around here, to get over you have to speed up, not slow down.

That's my fear, too. I really don't want to be cruising at 70mph and have to deal with a sudden failure or kick-down. I am torn on whether or not campaign 953 is just to be careful on newer models, or whether Hyundai knows something is up. They are finalizing a class action suit that makes the engine warranty lifetime. Given the issues they had with offices being raided, retaliating against a whistleblower, etc... it has all led me to being a bit more distrusting of them as time goes on.

Originally Posted by wemay
Type and viscosity of oil makes no difference if the vehicle has the issue. Every last one of the forum entries i've read on the Hyundai boards where a member gives background prior to their vehicle's demise has said they used top brand synthetics. Most used 5w30 (some Xw40 for turbo) and carried out meticulous maintenance.

Yep, another fear of mine, there are at least a few reports of people following the book or better and seeing a failure before 100k.

Originally Posted by 1978elcamino
Set aside 100 bucks a month for a year and a half. If in the next 2 years something happens you have already set aside the funds for a used engine for R&R.

It's covered by Hyundai up to at least 120k miles, and potentially unlimited if the class action settlement gets finalized. Money isn't a concern to me anyhow, it's purely a matter of the hassle.

 

[Propflux01]

Of course, this Camry you wish to purchase will never have an issue during its lifetime, correct?

 

[smc733]

Originally Posted by Propflux01
Of course, this Camry you wish to purchase will never have an issue during its lifetime, correct?


I will never understand why people get so defensive when discussing a product made by a multi-billion dollar company that they don't work for.

I am sure it will have some problems in its lifetime, but I am also sure it is much less likely to have catastrophic and potentially dangerous engine failure under 100k miles.

 

[Mad_Hatter]

Originally Posted by smc733
I've tried to stick to Top Tier stations as much as possible, and run either Techron or Gumout Regane before each oil change, but I realize the impact of this is limited on DI engines. Perhaps if I were to keep the car for sure, I might spring for dealer service on these items.

Unfortunately Top Tier and the pour in treatments do nothing for the valves and throttle body (a dirty TB can cause stumbling or hesitation, poor idle). Plus, what does your manual say about servicing the PCV valve. A clogged or sticking PCV valve can cause hesitation/surging. A stuck open or slightly open one can act like a small vacuum leak.

All of this can be done with some basic tools on a Saturday afternoon if you're the least bit mechanically inclined. On my Kia with the Lamda engine for example, it takes 5mins to get to the throttle body and 3 bolts and some clips to take it off for cleaning on the bench. And while that's out I'll inspect/clean/replace the PCV valve. I can't get to the PCV without removing the TB. When I put the TB on I could, if I were inclined to, spray some cleaner into the intake to tackle the valves (this part helps to have a friend behind the wheel to regulate the throttle). Like I said, not very hard just a little time consuming but you'll save a pretty penny v. a shop doing it. But your call, totally understand if "free time" comes at a premium for ya.. fwiw, in case you were wondering.. there are plenty of YouTube vids out there that can walk you through it. I know paying a shop helps keep the economy going ...‚, but I also like hearing it when people DIY it.

 

[Whammo]

Here's a quote from a Kia Tech on this forum awhile back: " Hyundai/Kia GDI engines really don't have coking problems on the valves. While the intake valves are open, the direct inject sprays a short burst of fuel that leaves the chamber and into the intake tract. This is done to rinse the valves with fuel and therefore fuel additive. You're really overthinking this. I've seen these cars close to 200k with no issues and just going to Jiffy Lube or Walmart for the cheapest oil. The Hyundai "Theta" engine has been a solid performer since it's inception over a decade ago. Direct injection was added 7 years ago. If there were any kind of coking problems, they would have been revealed by now.

If you do short trips, use a 30 weight synthetic for dilution. If you do long trips that let the oil heat up and burn off the fuel dilution, use a 20 weight synthetic. Hyundai says 3750 severe and 7500 normal for intervals. There are plenty of solid UOA's on here with 10k or more miles."

 

[Mad_Hatter]

Originally Posted by Whammo
Here's a quote from a Kia Tech on this forum awhile back: " Hyundai/Kia GDI engines really don't have coking problems on the valves. While the intake valves are open, the direct inject sprays a short burst of fuel that leaves the chamber and into the intake tract. This is done to rinse the valves with fuel and therefore fuel additive. You're really overthinking this. I've seen these cars close to 200k with no issues and just going to Jiffy Lube or Walmart for the cheapest oil. The Hyundai "Theta" engine has been a solid performer since it's inception over a decade ago. Direct injection was added 7 years ago. If there were any kind of coking problems, they would have been revealed by now.

I don't think that's physically possible. Once the exhaust valve opens/closes the downward stroke creates negative pressure relative to the manifold, in the combustion chamber. For injector spray to do what that person is describing would involve the intake valve staying open after spray and the fuel spray being sucked up into the intake, how that's possible with the pressure difference. Unless I'm missing something or got it wrong but i don't believe I do.

*edit: plus I don't believe the injector sprays until just before TDC and the valve is closed by then. Spraying much before TDC would evap most of the fuel due to high cylinder temps and/or risk pre ignition, wouldn't it??

 

[WhizkidTN]

Originally Posted by Whammo
Here's a quote from a Kia Tech on this forum awhile back: " Hyundai/Kia GDI engines really don't have coking problems on the valves. While the intake valves are open, the direct inject sprays a short burst of fuel that leaves the chamber and into the intake tract. This is done to rinse the valves with fuel and therefore fuel additive. You're really overthinking this. I've seen these cars close to 200k with no issues and just going to Jiffy Lube or Walmart for the cheapest oil. The Hyundai "Theta" engine has been a solid performer since it's inception over a decade ago. Direct injection was added 7 years ago. If there were any kind of coking problems, they would have been revealed by now.

If you do short trips, use a 30 weight synthetic for dilution. If you do long trips that let the oil heat up and burn off the fuel dilution, use a 20 weight synthetic. Hyundai says 3750 severe and 7500 normal for intervals. There are plenty of solid UOA's on here with 10k or more miles."


My experience with the 2.0L turbo engine shows that these engines do have a slow coking problem on the intake valves.
I ran 0W-40 full synthetic oil, had dual Oil Catch Cans (a very good version), used 93 octane Top Tier gas, did oil/filter change intervals of 4K miles, would annually run Redline SI-I fuel system cleaner and did the "Italian tune-up" regularly. At 77K miles, I have pictures of the intake valves of my "rod knock of death" engine back from Dec '18. It did have significant deposits on it. However, it did run great and had good mileage (given it had plenty of bolt-ons, an ECU tune and my slightly heavy foot).

 

[circuitsmith]

Originally Posted by Mad_Hatter
I don't think that's physically possible. Once the exhaust valve opens/closes the downward stroke creates negative pressure relative to the manifold, in the combustion chamber. For injector spray to do what that person is describing would involve the intake valve staying open after spray and the fuel spray being sucked up into the intake, how that's possible with the pressure difference. Unless I'm missing something or got it wrong but i don't believe I do.


Actually when the intake valve first opens the chamber may be at approx atmospheric pressure; and the intake manifold is at some degree of vacuum.
So exhaust gases in the chamber can travel from the chamber to the intake manifold.
Variable valve overlap, plus pressure/rarefaction waves in the manifolds can enhance the effect.
Many engines use this to take the place of a separate EGR system.

 

[circuitsmith]

Originally Posted by WhizkidTN
My experience with the 2.0L turbo engine shows that these engines do have a slow coking problem on the intake valves.
I ... had dual Oil Catch Cans (a very good version), ... I have pictures of the intake valves of my "rod knock of death" engine back from Dec '18. It did have significant deposits on it.


This demonstrates that IV deposits are not entirely (or even mostly) due to PCV fumes.
As I mentioned in my last post, some exhaust gases can travel from the combustion chamber and into the intake ports, past the intake valves when they first start to open.
And that is a source of intake valve deposits.

 

[WhizkidTN]

Originally Posted by circuitsmith
Originally Posted by WhizkidTN
My experience with the 2.0L turbo engine shows that these engines do have a slow coking problem on the intake valves.
I ... had dual Oil Catch Cans (a very good version), ... I have pictures of the intake valves of my "rod knock of death" engine back from Dec '18. It did have significant deposits on it.


This demonstrates that IV deposits are not entirely (or even mostly) due to PCV fumes.
As I mentioned in my last post, some exhaust gases can travel from the combustion chamber and into the intake ports, past the intake valves when they first start to open.
And that is a source of intake valve deposits.


This engine does not have a traditional EGR valve/piping but relies on the valve overlap to create the "EGR effect" for emissions, hence what you posit makes sense.
Interesting enough, my throttle Body was very clean and always has been (not even really needing a cleaning).

 

[Mad_Hatter]

Originally Posted by circuitsmith
Originally Posted by Mad_Hatter
I don't think that's physically possible. Once the exhaust valve opens/closes the downward stroke creates negative pressure relative to the manifold, in the combustion chamber. For injector spray to do what that person is describing would involve the intake valve staying open after spray and the fuel spray being sucked up into the intake, how that's possible with the pressure difference. Unless I'm missing something or got it wrong but i don't believe I do.


Actually when the intake valve first opens the chamber may be at approx atmospheric pressure; and the intake manifold is at some degree of vacuum.
So exhaust gases in the chamber can travel from the chamber to the intake manifold.
Variable valve overlap, plus pressure/rarefaction waves in the manifolds can enhance the effect.
Many engines use this to take the place of a separate EGR system.

Interesting. Admittedly VVT and overlap is not (obviously) something I know a heck of a lot about...that said, is there enough unburnt fuel in the exhaust gas to provide a cleaning effect on the intake valve? I mean isn't the whole idea behind DI is for a more efficient burn? So realistically, how much fuel could be left in the exhaust to wash/clean the intake valves? Is this a reliable means to cleaning intake valves on a direct injected engine? I'm not being rhetorical or intentionally obtuse, I'm just trying to wrap my head around how this works in re cleaning intake valves. This just doesn't seem like a reliable/efficient way to keep them clean.

 

[circuitsmith]

Originally Posted by Mad_Hatter
is there enough unburnt fuel in the exhaust gas to provide a cleaning effect on the intake valve?

There's plenty if fuel is injected immediately after the exhaust valve closes.

 

[Mad_Hatter]

Originally Posted by circuitsmith
Originally Posted by Mad_Hatter
is there enough unburnt fuel in the exhaust gas to provide a cleaning effect on the intake valve?

There's plenty if fuel is injected immediately after the exhaust valve closes.

In the scenario you propose, during what stroke is the fuel injected into the cylinder?

 

[KrisZ]

Originally Posted by Mad_Hatter
Originally Posted by circuitsmith
Originally Posted by Mad_Hatter
is there enough unburnt fuel in the exhaust gas to provide a cleaning effect on the intake valve?

There's plenty if fuel is injected immediately after the exhaust valve closes.

In the scenario you propose, during what stroke is the fuel injected into the cylinder?


With direct injection fuel can be injected at any point during the cycle. All manufacturers have different fuel injection timings and lengths, but one thing is common, all of them do not use a single fuel injection time anymore.

So with multiple injection and variable exhaust and intake valve timing, all sorts of things are possible there weren't before.
However I don't think any if that can be used to somehow direct the fuel in order to clean the intake valves.