lubox thank you for ur input

 

I don't think ETHANOL is your problems.

I've actually used 3 gallons of E85 in my car as a kinda test with about 1/2 tank of gas and car behaved normally...

 

^^^^^^ E85? you are asking for trouble. My siser used that stuff in her car and caused some serious damage to her fuel system in her Prius.

 

It's not the ethanol... i pump exxon super and the pump says the fuel may contain 10% ethanol and i'm not getting that feeling you are talking about...

By punching it, do you mean you are on the highway and want to punch it and that's when you feel it? if so, the car is in 8th gear and it has to downshift which can take a "little" while to get it in the right gear which may make you think she's "bogging" down...

 

jkweezy-I know the downshift feel but its the same downshift.

What about this:

If the AC is on prior, I shut the ac button off then I shut off the fan. Is shutting the AC off right before might have something to do with it?

Im taking luboxs' advice, Im going to the dealership monday to reset the computer.

 

mine has the exact same problem- im a certified lexus mechanic and im having a hard time figuring this out- car is 2012 is-f with 14000 miles on it- started doing this with about 12500- no codes at all. car runs like it has the MAF unplugged- no ***** at all- very surgy and hesitant- runs similar to an LS460 with the valve guide issue but much worse- resetting the ecu helps for a bit- sometimes for several hundred miles then the problem will randomly come back- has no consistency with oil or coolant temperature or outside temperature- only thing i came up with was the valve noise on this particular is-f is much louder than any other one ive driven- and ive driven several- and the bank 1 high pressure fuel pump was about 10 times louder than the bank 2 pump which is the exact same part number- so i replaced it under warranty, thinking that maybe the 'louder than the normal fuel pump' tick was tripping the knock sensors and causing ignition timing to be pulled way back- when i checked data list i found the ignition timing to be pulled to -15 deg. should be about +10-12 deg. seemed to help after replacing fuel pump but after driving about 1k miles, the bank 1 pump is just as loud as the other one was and the hesitation is back. i think its just a 2012 issue because there are no TSB's or tech notes anywhere on this- my dealers lexus rep had never heard of this issue being on this car before so no help or direction from lexus on it either.
im thinking it needs heads...
sorry for the long story- just wanted to cover everything.

 

Wow! Keep us posted on this please.....Thanks!

 

cmoDT!!! Thank You!!! Please keep us posted.

 

Try running the Lexus oil in it. A good friend had a GS 460 that ran like this with Mobil 1, and after switching to the Lexus (Toyota) oil, it stopped. I know it sounds bizarre, but it worked.

 

Unfortunately, it has only had the Toyota oil put in it. Lexus said they wanted me to capture 3 minutes of data list to email to them and they can tell if it needs heads or not. I will keep you all posted.

 

Yes it will if you run E85 only and your fuel system or computer isn't set up for it.

You can mix enough that it won't affect the fuel lines/pumps and wont cause the car to go too lean that it blows up... That's why I mixed only 3 gallons to a 1/2 tank.

I wouldn't be surprised if the car could run E85 just dandy with a tune.

 

Very interesting....why would the 2012 be different? I didnt think they changed anything in the engine design.

 

Very interesting! Subscribed.

 

Hello everybody, I've been watching over these boards for months and first want to thank everybody for all the information, its all been very helpful. I have been in the market for an isf for a while. I'm about to pull the trigger, I've been deciding to buy a new 2012 or a used 2011. I've been working with the dealer for a while, and have been able to get the Msrp lowered about 3k, so I could get a 2012 right now for 63ish fully loaded. I can also get a good deal on the used 2011. Like I said I was about to pull the trigger and going to just go for the new 2012 as its a good deal and the car of my dreams, but this thread is really scaring me. I couldn't imagine how I would feel putting my life savings into this 2012 and this issue happening to me, this sounds like a terrible issue that I don't even know how could be fixed. I've driven the 2011 several times and it runs fine, but I've never had a new car before and would love to start with this one. But once again this sounds like it may be a 2012 issue and I really don't know what to do now. Can you guys give any more updates on how this problem is coming along because I am staring to get worried now about getting a 2012 after reading about this problem. Any more info would be greatly appreciated, thank you.

 

Ok guys- turns out my car(can't speak for all ISF's) does not like shell gas. Something about the additive in their v-power is messing with the fuel system- I captured the data list for Lexus to see if if needed heads or not and they told me the data showed them it was running like it had bad gas. So I switched to a different brand- no problems.