2011 with 101k miles here.

 

08 w/151k. Compression test in May 2023 showed all cylinders at 190psi +/- 3psi

 

I'm at about 300 miles and no improvement, I'd actually say it's been the worst today. Those experiencing the issue, how are your LTFTs? Mine have been settling in the -20 range, both banks. STFT are fine when accelerating and idling but freak out at low throttle, causing the KCLV to crash.

 

That could possibly be a tune issue unless its something that just popped up. The first tune file I got from RR for the tuned intake (larger maf) wasnt calibrated properly and i saw -20 LTFT (fixed quickly with a new file). I would double check with Loi and make sure you have the right tune file for whichever MAF housing you're running (stock/mrp/rr).

Also look for any intake/vacuum leaks, especially around the MAF. You mentioned oil change, and the hoses that go into the HPS intake are pulling some vacuum on the crankcase. So any leak at the oil cap, dipstick tube, valve cover gaskets, aos etc could end up as unmetered air into the cylinders.

 

I've hady tune for a year and the LTFTs have always been within 1-3% so I don't think that's it. This weekend I'm going to thoroughly look for any vacuum leaks.

 

what is LTFTs & STFT? I’ll add it to my dashboard…thanks in advance!

 

That's short for long term fuel trim and short term fuel trim.

 

This is what Toyota says about LTFT, STFT, and Vf. These are all important parameters for fuel trim.

 

I smoke tested for vacuum leaks this weekend and found a small leak at the intake elbow to throttle body connection. I got it sealed up and my car is seemingly back to normal (fingers crossed).

 

I'm seeing a similar issue on a 2017 GS-F, bone stock. I did use Amsoil 5W-30 which was mentioned here. Filled the oil level all the way to full, but not over.

Resolved it by disconnecting the intake elbow and re-seating the air filter. I suppose it could have been a leak like the poster above, but wouldn't it have experienced the issue before the oil change?

From my thread:
https://www.clublexus.com/forums/gs-...il-change.html

 

A not-uncommon problem with the LS460 too.

Mine would do it with every oil change, KCLV would drop from about 28 to 4 or less after each oil change.

I’m a bit disappointed to see some ISF suffer the same fate.

 

I have never had these issues you describe. Are you sure the mechanics know how much oil this engine takes ? Every mechanic I tell looks at me funny. Get the filter from Lexus parts 2 5q jugs of oil from Walmart and either DIY or bring to oil guy . Half the beauty of this engine is we can work on it ourselves. Who do you trust more ? A oil change guy or yourself? If they were mechanics they’d be at a shop not in a trench . But sorry to hear this about your car to be honest hopefully you got it down pat. Luck

 

You must be past this now, but next oil change you can do two things.
1) monitor the KFV and KCLV after the oil change, if knock feedback drops below 4.5, lift off the throttle (the ECU seems to need to see sustained ‘knock’ to pull KCLV).
2) Drive in a manner that raises KCLV. In the ISF people put it in 8th (?) and floor it. In my LS460 I would accelerate super gently from 0-100 (km/h) and could get KCLV back up close to normal within an hour of driving.

 

Here are two examples where I monitored data at oil change. 1) is where I was on and off the throttle so KCLV was maintained and 2) was where I let the car do it’s thing. About 30 minutes driving to bring KCLV down from 31 to near zero, and back up to 28 (LS460).

 

I haven’t these issues ever at all but this guy seems to know his 460. This engine is pretty much bulletproof the way I see it

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