CouchRider

I just got a 2015 IS 250 AWD yesterday. Today, I first learned about the carbon build up issue and I'm (slightly) freaking out. I ran a lot of searches and read through tons of threads, and I think I got a good grasp of the problem but I wanted to just get some confirmation from you fine folks.

So here's my understanding, please let me know if any of this is incorrect:

If that all checks out then I can rest easy. I'd rather not have to pay for the cleaning, but I'll gladly do it if it means the car can continue to run as good as it does now. I'm just worried that even with the cleaning the gunk will continue to build up over time or something.

Thanks in advance for helping a newbie out.

JB5674

BG makes a few products and so does Seafoam. In my old car, I dumped 1/2 can of Seafoam into the crank and 1/2 into the gas tank. Drove the car hard for 10-15 miles then did the oil change. This helped keep the insides of the engine looking new and prevent bulldup. I had my mechanic take a borescope to the Pistons with 167k on the motor and he said the motor looked brand new. I'll be doing the same to my 350F AWD. Hope this helps

mello03

iTrader: (1)

What was your old car? I hope these cars don't have carbon issues like VA/Audi. Most DI engines get carbon on the intake valves that never see fuel wash over them so even if you add "additives" they aren't really going to help. I'm hoping Lexus has figured this out by now. Can anyone confirm?

dnasians

iTrader: (4)

That's where seafoam comes in. Put a third to a half of a can into the engine via vacuum line and it will clean off those valves

pillbox

I WOT through 2nd and 3rd gear at least once every two days when the car is warmed up, hopefully my carbon buildup won't be as bad.

I heard buildup generally occurs at low RPM and engine temps.

JB5674

I did this as well. Old car was a VW Jetta GLi Mk4 with every bolt on you can buy. Stage 2+ tune spiked 24 psi held 18.5 to red line. Revo SPS tune Boost 9 Timing 7

mello03

iTrader: (1)

Yeah that would get it. He said crank so I was just thinking that in the gas and oil isn't gonna help.

Loe

Putting seafoam into the intake manifold via brake booster will minimize carbon buildup issues, unfortunately not eliminate it. The "cleaning" offered by the dealer is pretty cheap compared to other brand car dealers though. Thankfully the is350 doesn't have this issue.

mello03

iTrader: (1)

So the 350 isn't plauged by the carbon issue? Not doubting you, just curious why. I'm assuming that it's because the 350 has a port injector as well as DI. Does that extra injector make the difference? I think it runs closed loop until it warms up for emmissions, and that will allow the valves to see some fuel for a short time. I guess that could make the differece no?

wfibear

The port injectors are exactly why. Because the port injectors on the 350 wash down the intake ports and valves at least part of the time every time you drive the car, carbon doesn't have a chance to build up with that engine.

Akai00

I still don't understand how engineers could make a ****-up like this. A high school kid who likes working on cars would easily point out this flawed design.

swaangin

I don't understand why people are offering solutions for this.. the carbon build up problem has been solved back in 2008. I don't understand the complete mechanics behind it but the engine works in a manner that it sprays fuel into the valves which essentially cleans the carbon. You won't have a carbon build up issue, I guess if you want to be safe then you can use the seafoam that they're recommending but this engine is old and tested.. It's lasted people 150K+ miles with no issues, you'll be fine

Sasnuke

The carbon buildup issue was resolved in 2011, so before 2IS lineup ended in 2013...unless you count the 2014 convertibles.
The 3IS 250's will have no more build-up than expected from a Direct Injection engine...which you have to expect some.
You can do a cleaning through the brake booster line and you can also install an Oil Catch Can in the PCV system...this will also help.

As mentioned before, the direct injectors do not spray on the back of the valves because the injector is located in the combustion chamber, along with the spark plugs and faces of the valves.
The carbon buildup occurs on the back of the face and up the stems of them valves.
On the 350 there are port injectors that spray onto the stem and the back of the face of the valves, therefore cleaning the carbon deposits at the same time fuel is injected into the engine.
While ALL engines will have carbon build-up, the design, maintenance, and care taken will ultimately determine how much.

E46CT

My understanding is that even the new Lexus direct+port injection doesn't really fix the carbon issue. Someone posted this from two 8AR-FTS engines (Lexus direct+port) that were brought into Lexus and torn down cause they threw CELs related to misfires. Here's the result on the intake valves at 60k miles:



once the carbon starts to stack on the valve seat, that's when you create sealing issues.

Sasnuke

I think before mass panic starts, we should clarify and separate out the two different issues here.
Firstly, the OP has a 2015 IS250...so all comments are in relation to the GR-FE family of engines...whether they have port and/or direct injection.
The 8AR engine is a 4-cylinder turbo, so it's like comparing apples and oranges now.
Clearly there is carbon buildup on the the valve in the pic, there is no denying that...however, it's also clear that something is causing the carbon buildup regardless of the fact the engine has port injection.
For that engine, the source of the carbon should be sought out first and corrected...my blind guess would be to look at piston to bore fitment.