jud149

I seriously doubt that this problem has anything to do with oil viscosity.

roadfrog

UPDATE:

So I removed several fuses from the underhood fuse panel - all ECU fuses, fuel injection, and the throttle sensor fuses, for a total of about 8 fuses. I left them out for about a half hour with the intention of the sensors etc to reset themselves.

It appears I now have success. It's been nearly a week and so far.....no hesitation. I'm cautiously optimistic the issue is resolved!

onepointon

Oil viscosity can definitely cause this. There is also a parameter the tech can look at on the techstream to indicate changes caused by this or other items.

When I get these types of complaints at the dealer and there has been a recent oil change, the first thing I do is drain the oil and put 0w20 back in it. It fixes a lot (not all) of the issues I see related to this.

jmcraney

Thank you for sharing your experience and views with us. I think there is some wisdom in what you have told us. But, tell us what you think would have happened with the problem vehicles if nothing was done. Do you think the vehicles would have continued to have this problem for the rest of their life? It seems to me that if this was a "permanent" problem it would be a much bigger story and a solution or some sort of action by the NHTSA would have resulted by now.

lieup

I just noticed my vehicle been having that issue. I've been using Mobile 1 full synthetic 5w-20. Could the oil weight cause the hesitation? Probably , going to try out 0w-20 and see if the issue resolve. Any one used 5w-20 having the issue?

roadfrog

Yes I used 5w20. But this was also synthetic. THAT was a first. The 5w20 was always used on my vehicle by the dealer, but it was dino oil. Regardless, the issue is now gone. But just for kicks, I'm gonna use dino on the next change and see what happens.

robert1408

Oil changes I did in January and now today with 0-20 synthetic both resulted in hesitation. Some had said resetting the oil life monitor might be a cause so I didn't reset it today. Same hesitation.

Why would changing the oil and filter cause this? My local Lexus dealer is aware of this problem but had no explanation. So I got to thinking, what could actually cause this? I can think of only 4 things in these engines where oil pressure excursions could possibly affect engine performance.

1 The oil pressure switch. The engine computer needs to know there is oil pressure available to operate the solenoid(s) for the exhaust cam variable phasers.

2) The oil pressure driven exhaust cam phasers themselves. ( Intake cam variable phasing is electrically driven on these engines)

3) The cam chain tensioner(s). Not sure if these engines use oil pressure operated tensioners but chain driven OHC engines often do.

4) The hydraulic valve lash adjusters.

Tonight I got the bright idea to check that the oil pressure warning lamp lit with the ignition on and then went out after start-up, just to see if the sensor switch was working. I did not know until now there is no separate oil light, just a master warning light. The owners manual lists several things this master light is for, but oil pressure warning is not one of them.

roadfrog

We really need to get to the bottom of this.

onepointon

Try disconnecting your battery and touching the car side positive and negative cables together. If they will not reach you can use a piece of wire to bridge the gap. This will clear out any stored learned values in the engine ecm. See if that changes anything. Obviously, DO NOT touch them together when they are connected to the battery, you will have a bad time.

Are you 100% positive you used 0w20?

robert1408

I used 0w-20 Toyota synthetic and did the oil and filter change myself. Did no resetting of the oil monitor either manually or through the OBD port. The hesitation and lack of power showed up right away. It was even worse the second day. Sometimes the car would just barely accelerate even at 4-5k rpm. On the morning of the third day, I disconnected both battery terminals and jumped them with a wire. It made no difference driving that day. It has now been six days and 277 miles and the problem is mostly gone. Power is still a bit weak below about 4000 rpm sometimes, then comes on strong.

I took the car to Lexus in January with this problem about a week after an oil change. They noted no problem on a test drive. I made that appointment on a Friday for the following Monday. Sure enough, the problem mostly went away over the weekend. The tech commented on the repair order that the "knock correct learn value never dropped below 25…knock correct learn value below 17 would indicate a problem. No codes stored or pending". The dealer did not charge me for this. The car is out of warranty so I was expecting to pay diagnostic time. Next time I do an oil change I'll set a service time at the dealer and do the oil change right before that.

onepointon

'

This is what I was interested in and one of the things that would reset with pulling the battery. 25 on that parameter is really good. Most cars with lack of power complaints are down around 13 or lower. When you pull the battery it resets to a default of 17. I have seen some with that value around 8 and the I wouldn't attempt to pull out in traffic. There are things that can cause that like mechanical issues, oil viscosity, previous overheating, ect.

Without driving the car myself, it's hard for me to say. I know you know your car better than anyone else, I would just be interested to see how it compares to another LS460.

robert1408

Thanks, onepointon. I'm taking this car to an indie shop owned by a good friend to hang some new front control arms sometime in the next few weeks. If it still has any power loss I'll see if we can test drive it and look at those knock learn values.

My Mom bought this car new in June '07 (mfg date April '07) and it's sure not been abused or overheated. The engine sounds good for a 460, certainly more mechanical sounding than a 430 but about the same as a 2008 and another 2007 I've heard idling. Those knock sensors "hear" better than I can.

The TSIB on this mentions a reflash that only applies if the knock learn values are good. My car had both the fuel rail and valve spring recalls done in 2009 and 2010 respectively. No ecm updates were documented and there's no label under hood showing one. If it is the knock learn values causing this problem, that begs the question; Why does it happen when you change the oil? I can live with this as long as it clears up in a few hundred miles.

sktn77a

iTrader: (2)

Shouldn't have to. That's not what we're paying for when we buy a Lexus!

lieup

I may try to clean the internal throttle body and see if the hesitation will go away. Overall, I don't think oil has to do with hesitation. I will keep you guys update.

robert1408

Well, I took my car to the dealer on Tuesday for a brake flush and told them about the hesitation/power loss since an oil change about 300 miles ago. I asked the service writer about re-flash for the pcm mentioned in a TSIB about hesitation on acceleration. I told him the car was running better now and that the tech might not find any problem on a test drive. I asked if they could perform the re-flash on a customer pay basis since the car is out of warranty. The service writer said they could but it might not solve the problem.

The car was ready a few hours later. The tech did experience some hesitation at part throttle and re-flashed with updated software. It was covered under warranty somehow, probably the 8/80 emission one. I am surprised how much difference it made, mainly a big improvement in how the engine and transmission work together. The hesitation is gone. Throttle response is softer and power comes on smoother in "normal" mode. In "power" mode the throttle and transmission action sharpens up nicely. I was totally not expecting a simple software update to make such a big difference.