MBTC

I looked up the VIN on the car I will pick up from the dealer on Monday, and it is later than the TSB mentioned in post #86 (here).

So, can anyone answer my question? Does this mean I dodged the carbon buildup issue completely?

XhyDra

iTrader: (8)

All IS250's should be covered, because if this was a VIN only case then there's more to this than it seems. You have to think if not every one was affected than there's certain parts in the powertrain that are different. That would suggest that there's a fix, but it does not seem that way.

This issue has not escalated to anything worst than rough idle and misfires. Until someone can post documented material stating that it damaged the car in some way all we can do is request a carbon-build up clean up if necessary.

There are several members on CL that have well over 100k on their IS's and haven't had to deal with this issue so it could be attributed to many things.

MBTC

Yes, they are all covered under warranty (I think that's what you're saying), and even out of warranty it sounds like the cleaning is not particularly expensive, so no worries for everyone else.

But, as I submit a noob question from someone who is a first time Lexus owner starting on Monday, do you understand my question? I'm just trying to map out what sort of cleaners I need, or plan my ownership of the car, etc... I'm the type to analyze everything like that

I'm just wondering if the fact that my VIN # from the Tahara plant, which is sequentially after the ones listed, means there was an engine change that fixes the issue at the root? If it happens it happens, I'm not going to be disappointed. Remind me to tell you guys how much I spent on wheel bearings and hub assemblies on my 2002 Maxima! And you never knew if you had the problem or not until it was too late (and dealers around here suck), thus my upscaling the brand a bit for better service).

You guys know way more about cars than me, particularly this brand, so I'm just asking a question and hoping to learn some things.

XhyDra

iTrader: (8)

My advice to you as a new owner would be, maintain your car well, don't fill up with low octane gasoline, always the highest available. And every 5k I would suggest dropping some Amsoil P.I.

MBTC

Understood and I appreciate the advice. But my question is, if my VIN # is greater than the ones listed in this SERVICE BULLETIN, does it mean there has been a change that fixes the carbon issue?

In other words, lets say my idle feels wrong when I hit 20k miles. Is the dealer in a position to say "nothing we can do, your VIN # doesn't qualify you for a fix"?

ohno

iTrader: (5)

Wot ftw!!!

MBTC

There will be some WOT, for sure.. honestly I really didn't buy the IS250 to haul-arzs.. In terms of HP I am downgrading from 255hp in my Maxima to a lesser powered engine but a better car overall. From someone who has seen $4/gal gas and drives a lot, I'm looking forward to the better gas mileage personally, 205HP to me represents the 80% of the HP in my previous car that I actually used once I tired of speeding tickets

However, with all the true gurus here, can anyone answer my question? Does this TSB mean I have nothing to worry about in terms of carbon?

XhyDra

iTrader: (8)

I'm afraid not
this is coming from someone that's constantly WOT the car.
Like I said in earlier posts I'm sure I run my car harder than most people here so WOT makes little to no difference.

XhyDra

iTrader: (8)

The TSB covers certain VIN's according to when they put together their data. Like the old infamous dust free brake pad TSB that only included certain model years but not the new models, it will eventually be updated as every model suffered from excessive brake dust. Some like myself didn't mind it. Others did, so some had a hard time having that TSB done just because their model year was not in the list. Your car will be no exception to this intermittent occurence.

In reality I don't believe you'll be having any major issues if you keep your car pretty much well maintenanced. The car is robust and reliable. And to say the least isn't much of a hassle. You have to remember that this issue is widespread but not everyone experiences it. So there are many things that can be contributing to the issue, something I'm aimed to find out.

In any case if you do ever experience this issue and the dealer won't deal with it, it's as simple as calling Lexus Customer Satisfaction and getting to the right people. Driving a Lexus is a pleasure, don't worry the car trully is reliable. I'm upwards to 62k and it's running like a champ

MBTC

I'm getting the impression that the dealer in my area is carrying the tradition of great service, so I don't expect major issues here, at least not in the initial years of ownership (and if it does become an issue I will bail and go with another car, brand-wiser than before).

It just seems to me, since this bulletin came out 6 weeks ago, that they would be opening themselves up to a potentially huge mess if they say "production changes" resulted in the elimination of the issue if it did not and the issue continues to occur. Especially after the accelleration recalls and such. What I'm really interested in is what (if anything) changed that would prevent the issue from occurring again? If there is not anything substantial that they can provide proof that was improved, then they pretty much are putting themself in lawsuit terrority if my VIN falls out of range and the problem continues to occur. Not that I'm lawsuit happy, it's just that I'm paying a substantial amount of money for a quality car and if the quality isn't there, they will hear from me one way or another. I will certainly give them the opportunity to make good on any issues.

I was mostly wondering how much of an eye I should keep on this carbon issue.. thanks for all comments, I'm keeping a hawk's eye on it for now

lobuxracer

iTrader: (2)

A couple of important things got missed in this thread. First, there is no external EGR on the 2GR or 4GR engines. EGR is managed through cam timing software, not through an EGR valve and associated plumbing. Also, huge misconception - EGR is Exhaust Gas Recirculation and has absolutely nothing to do with Positive Crankcase Ventilation (PCV). A catch can will pull even more oil and other condensates from the PCV flow, but Toyota have typically put a pretty large steel wool trap in the top of the valve covers (their PCV source) to help this process. Adding another can won't hurt, but I seriously doubt it will be a significant help.

Second - the WOT comment I made definitely DOES help reduce carbon build up by putting full thermal load on all the components. It helps reduce carbon build up on valves and valve seats (as does stronger valve springs which explains why the 3GS TSIB includes valve springs), and it will help reduce carbon in the combustion chamber. Adding water injection to this will further reduce carbon build up, but keep in mind, water injection when properly implemented will only run at WOT or heavy load. It won't do a lot at light load because there isn't enough heat in the process for the water to bring any good to the party.

IMHO, what cause the carbon build up isn't fuel or oil, but reversion from the EGR process. When the exhaust cam closes early to prevent all the exhaust gas from leaving the cylinder, the intake valve opens and there is a brief moment when the cylinder pressure is higher than the intake manifold pressure (you're at part throttle cruise, and there is significant vacuum in the intake) so you're getting a puff of exhaust gas up into the intake port because the moment the intake valve opens, the pressure in the cylinder is great than the manifold pressure. As the piston descends the pressure ratio changes and the puff gets pulled back into the cylinder, but while it's around the intake valve, carbon deposits will form because they're losing heat to the valve when they contact it forcing the carbon to stick on the metal.

I would suspect the people with the biggest problems would be those who do a lot of freeway driving - part throttle cruise - where EGR is greatest.

XhyDra

iTrader: (8)

^ Very interesting information Lance, thanks!

I figure that out of many of the things I've tried what didn't make sence is why the car still ran rough after long trips, this makes sence. You would think that the long trips would help it but instead it adds to the problem. I completely agree with you that WOT does help the problem, it's a temporary fix none the less, but it comes back days later. Luckily I've been able to test the car with several high rpm tests when it started to bog down. What helped the most is running the car in Sport mode for 15-20min in 3rd gear at 55-60mph, the problem didn't come back till months later. There's more to that method but that seemed to help. What I'd like to know is what would be a permanent method to say suppress this. I've sorta came to a few ideas but I'd leave time tell if they're good or not.

cchase231

I'm not the most mechanically educated individual, but this thread has me creeping toward the panic button. Originally I had wanted an IS 350, but ended up putting a deposit on an '07 awd 250 with 27000k on it because it had everything I wanted and I decided having awd in a michigan winter would be nice. After reading this I'm am starting to think I should just eat my deposit and get a 350, or a different make all together. What does this kind of thing do to the longevity of an engine? From the sounds of it a permanent fix is probably not going to happen.

IS-SV

^ Please, no panic needed and no eating of deposit.

quick123

iTrader: (2)

Ok, I really like your theory...you are right on the money with the part throttle cruise, these probably are the people that see this the most...and your theory also makes a good point about the EGR being the possible suspect, but doesn't really explain why this is really only seen in the 4GR and not the 2GR. The Lexus TSB only covers the 250, and most 350 owners are not complaining about this...the EGR system should be about identical on both engines, so if your theory is correct (which it very well might be), then we should all have this problem...

I can't stop thinking about the cold start injector that is only on the 4GR...that has to have something to do with all this...that is the only EFI component that is drastically different from both engines...I know that heat is needed for carbon deposits to form, so saying a "cold" start injector is to blame sounds silly...but it is located in the manifold and it does spray fuel...

Any thoughts???