Recently joined, first post -- and yes, it's another "I'm considering buying an IS, but what about ... ?" post. In this case, I'm seriously considering an IS350, but circumstances may wind up putting an IS250 in my garage instead, so I'm concerned about all the back-and-forth regarding the carbon buildup problem. I know this has been done to death on this forum; I've read those posts, and a lot of others on different sites. They range from apparent inevitability ...

... to nonchalance:

There are quite a lot of posts (here and elsewhere) about how you can avoid the problem; but what I wanted to ask is something different: how common is this problem, really? Is it something that's inevitable for all IS250 owners, or the exclusive purgatory of a very unlucky few, or something in between?

This may have been covered before; if so, I apologize for repeating the question, but I couldn't find the post. If someone could simply point me to that other thread, I'd appreciate it.

 

Well, this is what your average junkyard head has inside it.






While I wouldn't call it a serious issue, it's definitely something worth acting on every now and then. The 3GR from Japan in the car now was probably the worst I've seen. Not anymore.

 

I'll add to this it starts at the pcv. Look at junk yard upper intakes. They're completely coated with oil. Now imagine this going on for 50k miles, and short commutes, and never opening it up. Some seafoam will do some wonders, but that depends on how bad it is to begin with.
I'd say after you gain some ground just keep up with the seafoam. It sucks and all but this is short comings of a DI engine.

 

Ultra4,

Can you post a picture of the curve part where you see the most build up on the head. I think its the curve coming into the head to combustion chamber? If I remember correctly you dared me to run a coat hanger to check .

 

Ultra4 -- I guess that's why they're in junkyards. But what about the 250s that aren't in junkyards? How many IS250s never have this problem, or have it to a very minor degree, for every car that ends up on the scrap heap because of carbon?

Bearing in mind that I'll be buying a used car, another way of asking this question is: what are my chances?

 

It's the tumble cut on the far left edge of the pic there. That deliberate fan shape cast into the short radius of the port helps the air fold into the chamber, I guess. Given that prominent anti-reversion shelf and valve shadow, that's my best guess of it's purpose, anyway. Every single one of them is clogged up pretty bad in every 4GR intake port I've seen, especially under the SCV blades, which is why I sea foam so often. You can tell which valves are behind the SCVs in the group pic up above.

You have a 100% chance of a 3GR or 4GR in factory form ending up the way I show. Regular decarbonizing and oil catch cans are de rigueur with the 6-injector topends. The carbon doesn't scrap the head, just makes it run like a much worse engine until it's cleaned up...you can trash your bearings by running the same oil you decarb with, though.

 

Thanks I really appreciate it.

 

Okay, after poking around the internet a bit more, it seems there are an awful lot of people who ought to know who caution against having anything to do with the 4GR-FSE. So the IS350 floats to the top of the car list, followed by the GS350 and the ES350. Thanks for the input.

 

Eh, it's hardly a bad engine. The more I poke around inside it, the more I respect what the designers had in mind...they just didn't know about the carbon issues a GDI engine would have, because GDI was bleeding edge technology at the time. You can get and keep one carbon-free with just sea foam, CRC GDI cleaner, yamalube ring-free or anything similar, you just need to be consistent with treating it.

It's not like you're having to set valve lash on it every 10k like my vette needs. Solid flat tappets are super cool, but I'm absolutely going roller next cam...

 

It's not so much a bad engine as a risky one. Bear in mind, I'm asking all this for the purpose of buying a used car. I can't be sure of whether or not the original owner took action to prevent the carbon buildup from getting a good start; and besides, I want an IS350 more anyway. I might as well stick to the engine that gets better reviews for power AND reliability.

 

That's fair.

We'd have a 2GR if the clutch pedal wasn't mandatory for us. I'm still wanting to do a 3.5L if I can't max out the 4GR ECU with the 3.0L block.

 

I wish more 250 owners would chime in about how their car is actually used as I'm venturing to guess that those with driveability complaints in less than 60k mi are vehicles that do repeated short trips, never fully reach operating temperature and rarely if ever get opened up.

These same things will take out a healthy port injection engine too, it just takes longer.

 

OK well 2011 IS250 owner here. I bought my car at the lowest (and cheapest) mileage I could get because I saw A LOT of ads for IS250s with 200,000 and some even at 300,000 km. Higher mileage cars had different replacement items--you know cars are worn out/used up at a certain point...but if I can get even 50,000 km that might mean three years of use. And its a FUN car in manual, as others are pointing out in other threads...

My mechanic cleaned the intake and recommended 5,000 km oil change intervals for the carbon. NOT the catch can.

I try my best to avoid short drives but sometimes its impossible. 90% of my mileage is highway commuting to work or places.

I have heard stories of people buying higher mileage IS250s on here with good outcomes, at least in the short-term. I also see A LOT of higher mileage IS250s for sale, so IMO they can make 200,000 or 300,000 km with 91 gas and oil changes.

The IS250 is also cheaper than a lot of other cars so its a good option just on initial price. No car loan required!

 

Look here's an IS250 with almost 390,000 km on it: https://www.kijiji.ca/v-cars-trucks/...-base/m3782475

And it still runs and can be gotten some useful life out of, it seems. Like, its not being sold for parts. I've seen the same thing with 2001-2005 Toyota Celicas. There are lots of high mileage cars and there may still be life in them.

Walnut blasting is what, $500? $1000? If its ever needed, I'll get it and maybe the car will still be awesome.