TripleBlkF

I did a search and only found info on the IS250/350 regarding carbon build up to to direct injection issues. I was talking to an extended warranty inspector at my work today and, he has told me the V8 in the Lexus F (ie LS460 motor) has direct AND port injection... in other words... 16 injectors!

Is this true? To my understanding, with direct injection, the valves get carbon build up because there is no "wet" fuel/air mixture going past them that would keep em cleaner.

In other words... is driving our cars hard the best way to prevent it?

Is there a top end service to do in order to clean it up every 15k or so?

huksa

Yes, ISF does have 16 injectors....

UCrazyKid

Yes, the ISF has both a low pressure fuel system AND a high pressure direct injection system. At 32k miles I have had a chance to look at my valves and they are all very clean. The face of the pistons only had mild (within expectation) carbon build up. I add a bottle of Redline S1 fuel system treatment to my gas tank with every oil change at 5k miles.

lobuxracer

iTrader: (2)

The IS350 engine does not have carbon issues. Only the 4GR engines in the IS250s are suffering because they don't have port injectors AND direct injectors, only direct.

There is no need for top end service unless you run crap fuel or do a lot of very short trips.

LexyISF

The D4S is for combustion efficiency, so I doubt that carbon build up would be an issue.

streetx

iTrader: (4)

Havent heard of any issues on the ISF with carbon build up but pretty much what Ucrazy said

VtotheJ

iTrader: (2)

The previous owner of my car had fuel injector replaced. So I assume my valves are clean?

jbjones85

iTrader: (20)

I'm pretty sure that only the 250 is prone to the carbon buildup issue. I go by the "get on it every now and then " theory to keep everything carbon free.

UCrazyKid

For reference, ISF valves and Pistons with 32K miles on them:

SargeISF

iTrader: (6)

I just did a complete Seafoam oil, and gas treatment on my ISF. One oil change after, and its clear as a bell. Over 90K on my F.

isfvss

OK this is old but does anyone know why this motor was rebuilt ??

LexusfanVA

iTrader: (1)

https://www.clublexus.com/forums/car...t-74-days.html

UCrazyKid

Here is a permalink to the pictures. https://www.clublexus.com/forums/car...ml#post7130713
Short story: engine making rhythmic but in consistent knocking noise. After 1/2 dozen dealer visits Lexus Corporate OK'ed an engine teardown to find the issue (@ 35,000 mi). Engine was completely torn down and all parts measured and inspected by 2 engine builders (one Lexus, one independent).
The findings: The valve springs were failing (short or deformed) like the Toyota V8 valve spring recall, the thrust bearings on ends of he crank shaft had premature wear, one cylinder was out of "true" (flared as it approaches crank). Engine completely rebuilt, new springs, cylinders honed, new piston rings, new crank bearings, new water pump, new oil pump, new gaskets, new "stretch" hardware. Time ~3 1/2 months, cost ~$16,000 charged to Lexus Corp for warranty work. Car is now at 75,000 miles and has run perfect ever since. No noises, better power, smooth. Driven as mostly a grocery/kid getter with occasional spirited driving. No track use.

Leander311

iTrader: (2)

^^^This. Just sold my IS350 w/195k (as said, has port/direct FI just like our IS-F's). Drove/tracked the **** out of her. Was just starting to use a little oil, but a BG Products EPR service took care of that.

A few things to help ensure a clean engine, in order of importance:

- Use quality gas. Anything designated "Top Tier" will have 3-5x the EPA-minimum level of detergents. Shell is arguably the best according to a few passionate tribologists. New stations w/new tanks are also good in theory. I use Costco, because it's Top Tier gas, it's cheap and on my way home, I know the tanks are new and clean, and I know the guy blending the detergents into the fuel. He's ex-military and does not f*&k around!
- Use quality oil, i.e. a reputable synthetic with low NOACK volatility. Pennzoil Platinum/Ultra, Mobil 1 EP, and RLI Biosyn are among my top choices for their solid $/quality ratio. If you're changing every 5k, even a quality "dino" oil will suffice for most drivers... PCMO standards have improved incredibly in recent years.
- If your IS-F is mostly a grocery/kid-getter and thus typically sees short trips, ensure you occasionally drive her hard AFTER the oil is FULLY up to temp. Notice this can take 2-3x as long as getting the coolant fully up to temp... This fact is not inconsequential.
- If you start using more oil than you're comfortable with, try a BG Products EPR treatment. I was skeptical as a mechanical engineer with a b/g in ICE design, but the science and results behind this are quite sound. Best $20 I ever spent on the IS-350.
- Use an AOS if you are in a hot climate, drive hard and/or track your car.
- Fill oil only to half or 3/4 up to "full" on your dipstick. The fact our sumps hold nearly 10 quarts is not for lubricity, but rather for cooling and longevity. This also from a tribologist I trust.

Quadrphnia

Totally. I've got a BG oil treatment on the shelf I'm going to do first thing in the Spring along with another carbon blowout. Can't wait - my buddy swears by their products too. I either use Shell or Mobil gas & seem to have better performance with Mobil. Never thought about the age of the tank, that's funny & makes perfect sense.., There's a Marathon by my house that has an outstanding commercial loan (which is also delinquent - I consult for the bank) to repair their leaking tanks. Glad I never stop there.