I have read about the carbon build up problem in is250, why it happens, and how it affects the car. I have come across a few solutions to the problem but I am now sure what works and what doesn't. If you have tried something to avoid/fix the problem, I would love to hear about your experience.

Apart from the engine rebuilding from Lexus, I have come across two types of solution -

1. Slow down carbon build up.
This can be done by installing a catch can which blocks the oil vapors and carbon going from crankcase to intake valves. Theoretically it sounds a good solution but does it work in real.

Another way to slow down carbon build up is drive hard regularly. When you drive easy, more air from crankcase is sent to intake which means more carbon buildup.

2. Clean up the carbon occasionally.
I have come across quite a few options for this and not sure which is the best or easy DIY or cheapest. Some of the options are -

1. Lexus service top-engine cleaning. (How often do you have to do this?)
2. Put seafoam in in throttle? (not sure how exactly this is done). Valvoline has a service similar to this -
   About Valvoline EasyGDI - YouTube
3. Open the engine intake manifold, close the intake valve, and apply some cleaning agent to the valve. Cleaning agent can be either chemical or physical (walnut blast). After cleaning, vaccuum out the cleaning agent. (How much does this cost?)
4. Italian cleanup. Drive the car at high rev for sometime (10-20 min).

What solutions have you tried? What's your experience with the solutions you have tried?

 

Drive it hard. I have 06 is250 with 160k miles. only had to rebuild the transmission. Other then that no issues with the car

 

Here are my thoughts on the carbon issue that the IS250's have. It seems that Direct Injection and the PCV System are the two major sources of carbon build up.

I have watched enough videos and used the product myself to feel confident that SEAFOAM works the best. You need to buy the can with the straw that slips into the throttle body/intake after the MAF. I would recommend doing this treatment at least every 3000 miles. Chrisfix on youtube has a video you can find here:

Does Seafoam Actually Work in a Car? (with Proof) - YouTube

You could also very carefully pour SEAFOAM (regular can) very slowly into the vacuum line from the PCV to the engine. Use caution and just pour about a 1/3 of the can in (very slowly). Use the other 2/3 of the can just before your next oil change. All you have to do is pour it into your engine (through the oil filler) and let it run for about 15 minutes. Then drain and fill with fresh oil.

Here is something I have been thinking about and I think it may significantly reduce the carbon build up. I'm open to any suggestions if you see a problem here.

First thing I would do is plug the vacuum line that runs to the PCV Valve. I would then take out the PCV Valve and insert a fitting or adapter that looks like this:

http://pressureconnections.com/produ...ARBS/4501.aspx

I would make sure that it has the correct threads and that it is a 3/8" hose barb. After substituting this for the PVC Valve I would run a 3/8 hose along the firewall and down to the side of the Master cylinder and make sure that it mounts somewhere below. The last thing I would do is put a G12 Fram Fuel filter on the end of the hose that runs from the 90 Degree barbed hose fitting that replaced the PCV Valve.

I believe this would provide adequate crankcase ventilation and would not affect the vacuum of the vehicle.

You would avoid sucking all that nasty oil and vapor back into your intake and top end of your engine that is causing carbon buildup. A catch can will help but why not just eliminate the problem entirely by venting the crankcase like all vehicles use to and some still do.

 

how much for rebuild transmission? Can any transmission shop do the work?

 

IS250 will alway have carbon buildup because of direct fuel injectors. Didn't want to deal with the issue in the future so we trade it in for another Lex now own IS350/ES350

 

Hey why do you think your tranny went? was it to do with driving style? paddle shifting? etc please let me know.
These cars have good trannies though right?
thanks,
Mitch

 

is350 doesn't have direct fuel injectors?

 

the 350 has direct and port injectors so it bypasses the issue completely as the fuel washes over the intake valves essentially constantly cleaning them.

 

Carbon build up is due to poor quality fuels, poor filtration of EGRed fuel residuals and poor ring and valve guide film seal in the engine. Keeping them down is very easy and simple. However, once a deposit forms, good luck, they just continue to grow. Unless you use Ethanol or cleaning agents.

Using a quality oil + filter + fuel, and you would never have any of these deposit issues. Occasionally I use VP's fuel system cleaner to keep things clean, but merely as an insurance and more of my desire to try and nail the perfect combo. You can try running E20 for a small amount of time and then go back to E15, this will help to reduce some deposits formed.

Catch cans will reduce the EGRed residuals but it's just that, reducing. Those deposits can't be treated physically because they are polar. If you have a fuel and an oil that can achieve solvency post combustion together than you will have no issues.

This is an argument that gets sparked in lots of other threads with guys saying, we've never heard of these issues! Yeah, until the car gets to this age, then the negligence starts to show.

 

What was the problem/symptoms in the transmission before the rebuild?

 

On the 250 NO fuel passes by the valves so it makes no difference.

 

It has an EGR, fuel residuals go past and stick on the valves as they're recirculated. Yes, makes huge difference.

 

No have EGR,have PCV

 

Thanks,

Did you ever try replacing the PCV valve with a fitter or adapter? Any luck?

 

YES THERE IS EGR.

PCV will have nothing to do with this. Deposits forming due to lack of solvency from oil + fuel, and poor valve guide seal and poor ring seal from off the shelf oils or worse, Dealer Oils.