Very interesting read, I always looked at it as, lower octane Fuel in a High compression engine would sort of have a diesel effect, the mixture lighting before the spark would light it off, and that a higher octane would be more resistant to it because of the slower burn and being able to resist that auto ignite slightly longer till the spark sets it off

Cools stuff

 

The gasoline FAQ is a great read when you're curious about what is really going on. It takes awhile to read all four parts, but it's well worth it if you ever want to tune an engine. It dispels a LOT of myths out there.

 

Just got off the phone with corporate. Their position is the same as the dealers -- "tech can't find the problem therefore there is no problem".

I went round and round, mentioned the scores of other IS250 owners with the same problems, the LSB's, etc. etc. They won't budge, and were even kind of rude about it... like I'm making all of this up.

 

You sir have all the right answers... Why do people keep going on around this issue when the technical s are presented to them is out of my mind...

CypressIS... It sucks the tech didnt get to read a code, your car was in limp mode and it is quite possible it didnt record any codes. Lexus corporate has to stand behind their techs, even if they are not doing their jobs... looks like your problem is your dealership, not corporate. call them back and arrange to bring your vehicle somewhere else maybe? leave there for a few days and ask for the manager or shop foreman to take it home. someone along the lines should get it to act up.

 

I posted about my theory of this being an issue primarily in warmer climates a few months ago. I since have bought an is250. I believe that my theory was generally accurate. I notice that during cold startup the engine idles high for around 2-3 minutes. I believe this is likely enough time for the cold start 7th injector to provide enough fuel flow over the intake valves to help clean them of carbon buildup.


I also believe that the "answer" to this issue could be solved either by re-programming the cpu to run the 7th injector occasionally and adjust fuel flow from the direct injectors. My suggestion would be to run the 7th injector anytime the vehicle is at idle. There is no benefit from direct injection at low rpms, and I don't believe there would be a meaningful difference in fuel consumption or emissions.

The alternative option would be some custom version of a signal interrupt. I believe one could piggy back a signal off the accelerator, add an interrupter to the 6 cyl. injectors, and to the 7th injector. When there is a "0" signal from the accelerator, you would shorten the duration of the direct injectors and add a signal to the 7th injector. I would also tie in a signal from the 02 sensors to ensure a proper mixture at idle. Once the accelerator reaches a non 0 state, the system would cut out and return to normal Lexus fuel management. I think this could be done with a relatively simple programmed chip on a relatively small circuit board and a handful of lexus factor plugs to intercept the signals. The key to making it invisible to the ecu would be getting the fuel map correct out of the 7th injector and making the transitions very fast, and you'd have to calculate when to have it occur such that the direct injectors never skip a squirt, and the fuel from the 7th injector in the intake is consumed so that you don't get a brief rich fuel signal from the o2 sensor.

Anyway, I think $2-300 in parts plus some programming and engineering time could result in a real solution. And if it worked well enough it could be extrapolated to other "problem" cars like the VAG direct injection cars with the same issue.

My first step in designing the right system would be to look at the URD 7th injector kits for forced induction toyota v6 engines. I suspect they would make a good starting point in terms of how to design the interfaces.

Anyway I live in cold weather climate, so I don't think it will ever be an issue, but if the time comes, that would be my plan.

Good luck.

 

I live in Indianapolis, IN, and I am at 28,000 on my 2008. So far (knock on wood as they say), I have not seen any of these problems. I do run premium gas at all times and use Mobil 1 oil. With about 4 months cold weather here, I'm guessing the 7th injector is active. Hopefully I won't have these issues.

 

If its In limp its going to def record codes. If they clear on the next ignition cycle like these carbon cars dO, theres still a record in the "misfire monitor EWMA" which keeps a misfire count completely separate from any codes being set. My example, i did the top engine tsb @ 30k, i never had a concern.. I let the car sit for a week now @ 66k and it barely ran, i had misfire on cyl1 current and pending on 2,3,4,5&6. I tried something diff this time, next week im pulling the manifold and taking pics of my valves & will post them.
I set the RPMs to 4k & injected a cocktail thru a vacuum port ontop of the manny. A full bottle of GM top engine clean, 2 bottles of Toyota top engine clean & GM top engine clean bottle refilled w washer fluid. We'll see...

 

I'm really excited to see the results of this.

 

Well after my "I do not want to pay a diagnosis fee" email to the dealer, I hadn't heard from them in a while.

Yesterday a service adviser called me at 9am and then again at 3. I missed the earlier call and answered the 3pm one. It was this awesome guy Mike who said he'd scan the car for free. It's been more than a few weeks since the limp mode happened, but I agreed to bring it in for a quick check just in case.

He also mentioned "we are not doing top engine cleans anymore, there's another fix" which we all know what that other fix is.

Talk about amazing, this is why I bought a lexus, a chevy guy would NOT call me up offering a free diagnosis after I've bugged off and the dealership won the argument!! I will def be shopping at this dealership for my next car (Greenwich)

Question if they offer to do the rings/etc, should I take it?

 

Absolutely^^^ Sounds like the same exact thing my dealer did for me. Take the work iff they do it under warranty

 

Okay, I'm having these rough idle problems on my IS250, but i have no misfires or code, just a rough idle and sometimes a shaky car like it's about to die.

I've told my dealer (Sterling McCall Lexus (Houston TX)) about it, and they refuse to do anything because there no codes and they cannot "duplicate" anything.

I know i have this problem because i am the daily driver of the car, how are they going to argue that?, but they sill refuse.

What Should I do?

 

It just happened to me on the way to work on the freeway. It really bothered me though the car was going to die, scheduled an appointment with the dealership and they mentioned that diagnostics will be free under warranty and they will let me know how much based on what they find.

 

Bumped....

 

Well I for one am THRILLED with how Lexus is handling this issue and they haven't even said they'd change anything yet.

I'm just thrilled that they are taking me seriously and are taking a look at it on their own dime. That's all I can ask for.

They also gave me a new ES with 400 miles on it to keep until it's done. I don't have to worry about any gas in the loaner car EVEN IF THEY say there's no problem with mine.

So at this point:
- They took me seriously even though I can't prove the car has ever done anything wrong
- They are looking into it for free
- I get a NICE loaner car till they figure it out
- They might even change all the parts even though it's been working fine for 3 weeks.

I've had chevy's and fords. It was always a miserable experience trying to get them to fix known "TSB's" even under warranty.

Even if they don't replace anything, I'm pretty much sold on a company that will listen to me as a customer.

 

How is your car running?