lobuxracer

iTrader: (2)

EGR is the same for both. The port injectors are used for mid-range torque and are not used for WOT according to all the documentation on the 2GR, so it's pretty likely they're spraying fuel quite a bit of the time. Thermal shock is the best way to remove carbon and the fuel is going to present thermal shock to the intake valves to help keep them clean.

The cold start injector only runs for a very short time. Essentially just enough to get the engine started. I really doubt it could be responsible for this problem. What might be interesting would be to have the cold start injector spray during part throttle cruise conditions to minimize the carbon formation on the intake valves. This might be what Lexus is trying with software right now.

If I were a 250 owner, I'd be looking at installing an Aquamist (or some other reputable manufacturer's) water injection system. It will keep the engine cleaner than anything else you can do. You just have to remember to keep water available for it to spray.

FWIW, I worked on a Mini back in the 80s with a serious carbon problem. The intake ports were nearly fully blocked because the carbon deposits were so unbelievably huge. It had a valve stem seal problem, so as the oil leaked down the stem, it formed huge carbon deposits. I removed the carbon, faced the valves and seats, did a light street port, and it ran like a charm. The owner was amazed at how much better it could climb hills. But even with the ports nearly fully blocked, it didn't have idle issues.

ABC

I haven't read the entire thread, but just wanted to post what I've experienced.

2006 IS250 (auto rwd) with ~45k on her. I've had the rough idle about 10 times total over the life of the car, with 75% of them happening in the past 6-9 months. Every time it happens, i drive the car harder, WOT for a few runs and it seemingly goes away. I always thought it was carbon and maybe i granny the car too much

Clay Easto

How do you do WOT? Are you just flooring it to get up to speed?

ABC

i put the car in 1st and either slowly climb up to redline (so it heats up nicely) then in 2nd to do the same... I hate doing it for much more; i worry about the tranny at times... or I just WOT at times depending on if anyone is around and what mood i'm in It's easiest to do this entering a highway.

After i do that, the problem usually goes away for quite awhile. I had 2 rough idles 2 weeks ago. After the 2nd one, i drove the car hard for about 5 min and i haven't had a rough idle since... We'll see how long it lasts.

MBTC

When I heard of the latest recall, I was glad to learn my new IS 250 isn't on the list, but it sounded similar to the carbon build up issue symptoms:

June 20 2010 Recall

SC3coupe

iTrader: (4)

Anyone saw the commercial about toyota investing 1 million every hour to improve safety?

Water injection and/or methanol injection do wonders to clean the intake valves and combustion chamber, almost like steam cleaning. On a non forced induction car it would have to be tuned carefully for much smaller amounts to not choke the engine, the good thing about methanol is that it's a fuel and you would only run a little more rich, but it has not crossed my mind to install water or alcohol injection on a car like IS 250 :/

Not sure about the WOT thing, with alot of carbon build up on the valves, the sharp edges of carbon will grow red and cause fuel to pre-ignite, which isn't so good for the engine.

The symptoms described bad idle and stalling, misfiring, due to old, gummy intake valves does happen on my AE86 but that engine is 25 years old..

What is the point of the direct injection anyway? Seems like the new cars have more and more technology in them without through research on performing a long life of at least 200k miles.

I still feel the IS250 is build quite solidly and hope toyota can come up with a reasonable solution soon. alot of time different engine have different "quirks" and I think is considered minor although probably not quite acceptable for Lexus standard.
Mitsubishi 4G63 crankwalk anyone?

lobuxracer

iTrader: (2)

I'd recommend reading Sir Harry Ricardo's seminal work in this area before saying something like this. You can put a ridiculous amount of water in an engine regardless of induction style without ill effect.

SC3coupe

iTrader: (4)

Just saying on forced induction engines typically seeing 400HP or more, and 200HP IS250 engine should be tuned less.
I have had engine bog down and sputter when the injection is set to come on too early. Probably bad tuning or parts selection on my part. Since then I upgraded to a system a pulse width modulation acting as a 5th injector on a 4 cylinder engine with with variable amount of spray based on load.
However that is not something I can see myself installing on my 2IS.

raptor22

it sounded similar, but it it's not the same. It's a mechanical issue involving the valve springs.

from another thread:
https://www.clublexus.com/forums/5608411-post17.html

king06

iTrader: (1)

So i was reading over the thread on the new valve spring replacement recall and i ran across a couple is350 owners that have had the exact same symptoms that is250 owners have experienced because of the supposed carbon build up. So does this mean that it is possible for the is350 engine to have the same issue that the 250 engine has.
Compare the symptons that golfproatl states he has in post #30 in the valve spring thread with the symptons some is250 owners have posted in this thread. They sound like the EXACT same issue.


This is the post i am referencing from golfproatl

quick123

iTrader: (2)

Every engine has potential for carbon build up...but the 4GR is having an issue with EXCESSIVE carbon build up which has not been seen on the 2GR, which is why the TSB only covers the 4GR.

panda327

iTrader: (3)

anyone got a video or an example of the idle vibration i hear some members getting ?
are our cars suppose to experience no vibration AT ALL not even the slightest shake?

quick123

iTrader: (2)

A vehicle with excessive carbon build up will produce a low/rough idle very similar to a vehicle with a vacuum leak...you can see the engine shaking if you pop the hood, you can even see the doors shaking if you open them, and sometimes you can see the tops of the front seats shake...nothing that is scary, but something that most Lexus owners have never experienced

king06

iTrader: (1)

You mean excessive as in a lot of carbon build up within a particular engine, or excessive as in way more is250's are experiencing the problem. If its the latter that might just be because there is significantly more 250's than 350's and we just havent seen as many complaints because of statistics.

quick123

iTrader: (2)

No...excessive as in the 4GR builds up a lot more carbon than the 2GR, that is why you see the TSB only covers the 4GR...