Trumpanche

celebration was indeed premature. Anyone here besides RoadFrog cleaned their MAF sensors? RoadFrog - how did the timing of your MAF sensor cleaning correlate with your performance improvement? Wondering if it wasn't just your oil change regimen that helped you.

jfattibe

Sorry to hear about that Trumpanche, Just wondering, did you have the ECU and transmission updates done when you had the oil changed ?? If you did I would think that would have cleared things up ???

roadfrog

Well ****e...that sucks.

My MAF cleaning had no correlation in my case.

Trumpanche

Jfattibe - ECU was flashed at 96k and transmission at 101k.

FastTags

has anyone experienced hesitation with acceleration on 2009 and up models???

or it only effects 2007-2008 ?

7milesout

Question about the hesitation - But first to provide a data point to FastTags.

I have a 2010 model. Barely 20k miles on it. Miles on the car could be a contributor, that's why I mention it.

I have only performed 1 oil change on it during my ownership, and I refilled it with 5W-20 Castrol GTX Conventional. That is the brand and weight my local Lexus dealer stated they refill in all their customer's LS vehicles, unless the customer specifies synthetic. I didn't ask what they used in that case. I did the oil change the old fashioned way, by myself, in my garage.

My car has yet to have any hesitation. 5W-20 conventional, no hesitation. But IMHO, I have to think hours on the engine is a significant contributor. I could be wrong, the guys with the hesitation might mention their odometer readings. So maybe I'll have hesitation in the future, dunno.


QUESTION ABOUT THE HESITATION

When you guys WITH the hesitation experience this, is it from the initial push on the accelerator pedal from a DEAD STOP, or does it happen at some point during the PROCESS of acceleration? Don't to try to read anything into my question. Because there is nothing there. I'm just trying to understand / imagine this hesitation since I have yet to experience it.


7milesout

jfattibe

For me its usually when I am going around a corner at approx. 15-20 mph and in second gear. If I put the accelerator down halfway or more the hesitation is there. For me, I only have a little hesitation but I've noticed it does seem to return in full after driving stop and go in traffic ?? wondering if heat plays a part in this ?? but then after a good highway run it seems to dissipate. I did my oil change 800 miles ago with Pennzoil Platinum PurePlus synthetic 0w-20 because I heard ticking upon start up figuring there was dino in it. Still have the ticking upon start up? But I feel better knowing what's in there. I have 88K on my 07.

Doublebase

I've had it somewhat like the way jfattibe described...kind of a hesitation upon rolling from 15-20 mph. I've tried different oils...TGMO, Mobil 1, Valvoline Syntec, but it didn't make a difference until I started using better fuel. What I was doing, I was alternating between super and mid grade every other week. Now I only use super and it has improved quite a bit. I still get it once in a while, but it's very infrequent now, whereas before it'd happen a couple times a week.

Trumpanche

Cleaned my MAF sensors. No change - they looked pretty clean already (and it's hard to see down in there).

I think I am now able to induce the engine hesitation. My trick has been to set the cruise control between 45-50mph (which settles the engine in the 1500-1600rpm range). After a few minutes of steady cruising at this level, I have noticed the engine starts to sort of get unhappy and the transmission shifts to hold the speed and it just seems to get upset. Following that behavior, the next stop light has extreme hesitation. I always thought the problem was cropping up while waiting at the light, but now I'm thinking it's during that moderate speed cruising. If I can reproduce it a few more times, I'll bring it back to the dealer and see if they can analyze it under those conditions.

Note that at 2k RPM (80mph), this never occurs - I just took the car on a 1000 mile road trip and it behaved fine.

I am wondering if the fuel trending starts to go south for some reason at this slight throttle opening and then takes some time to trend back to normal later. Maybe a dead spot in the TPS sensor? Dirty throttle body? Any likely culprits?

satiger

iTrader: (1)

Does this happens only when you use the cruise control between 45-50mph or even without cruise control but between 45-50mph speed?.

7milesout

This to me sounds like the knock sensor is involved. I mentioned in another post that my LS will run extremely low rpm at 40 - 50 mph. It's lower than what I would run if this were a manual trans I was operating. But my car has always ran real smooth. And a modest push on the throttle it shifts down. But generally cars lug at a low rpm like this. And "pinging" can be a product of lugging. Pinging can be so light that you cannot hear it. But the knock sensor can.

If this is what's happening (which I don't know, but think it's possible), the detection of pinging / knock / predetonation would be countered with retarding the timing. And performance suffers with retarded timing. And would have to believe the computer is programmed to endure a set amount of time with no knock before the timing would be allowed to its full advanced setting.

This begs the question Trumpanche - Do you religiously fuel with premium? Premium in my area is 93 octane. Is your premium lower octane than that?

Just questions here - because this still doesn't relate to this behavior immediately following an oil change.

Lexuslsguy

Check the link below. Oil consumption is also explained.

http://carspecmn.com/ls460-and-ls600...g-andor-p2119/

satiger

iTrader: (1)

Thanks Lexuslsguy for sharing the article. An informative article. However, what causes valves to have (create) excessive clearance?.

Lexuslsguy

The valve stem guides have a design flaw which creates free play in the valve. This in turn promotes oil consumption and of course play in the valve. The knock sensors engage causing the car to retard the timing creating hesitation.

Doublebase

I don't think this explains everyone's problems, my car for instance doesn't use hardly any oil at all. I can go 5k miles and only use 1/2 a quart - I consider this to be excellent, yet I do occasionally get this "hesitation". For me I think it was the fuel I was using. Also I don't run into many people on here that have excessive oil consumption issues, and I've never heard anyone complain about blue smoke coming out their exhaust pipes upon acceleration, etc. I have read those valve guide reports and it doesn't seem to be a problem that affects many people - although I agree that it would cause the knock sensors to actually engage and perhaps cause a hesitation, but fuel would do the same thing because of pinging.