MacroP

I've had the an 08 LS46 for nearly 3 years now and the hesitation issue came about around 6 months into ownership. The first hesitation issue (obvious audible timing retarding) was not after an oil change actually but the car had just sat overnight and drove like a pig in the morning. Car had 74000km (50k mile) and now has 95000kms. It has had 3 oil changes (by me) since and every time the hesitation returns on the first drives so to me it is clearly definitive - as crazy as it sounds. It takes a couple hours of driving to recover however for the me the hesitation never fully goes away. There is still a lot of timing retardation going on at low revs off the line - it is a distinct induction growl that is all too familiar. The timing retard also cause the transmission shifts to be all of over the place which exacerbate the driveability issues. Top end power about 80% there and I still fell a little hesitation and it is not smooth power delivery when revving. My LS430 has better off the line pickup now where the 460 used to blast this thing away. I remember when I got the 460 thinking to myself that I'm going to lose my licence sooner than later but not anymore.

I took this to a Lexus dealer recently here in Oz (several hours drive for me) for diagnosis and they wouldn't really take me seriously about the oil change cause and with their test drove, said it drove fine but I know my cars well. I drove an identical 460 lately (with 220k-km on the odometer) and this thing was like a rocket ship. Was disappointed with the Lexus response as many other members here have clearly had identical issues under the same circumstances. There is no solution here in Oz for a firmware upgrade and the US TSBs don't apply here.

So today, I pulled the cover off the engine ECU box in the engine bay and stuck some back probes on the 4 knock sensors going to the ECU. I hooked up my bench scope in the garage and could see the sensors spitting out a nice AC signal (2.4VDC bias). Even at idle I was getting a 400mv spike every 4th batch. All 4 sensors were doing the same. I really need a 4 channel potable scope and record real-time under heavy load. I do have Techstream and can already see the timing going backwards heavily when lead foot driving. My plan was to eventually attenuate the signal slightly to prove the point. More to come.

PS. I am curious to see the oil change scenario re-occur as I want to test a theory that it might be the actual oil filter change with the oil starvation that occurs for 1-2 seconds, causing the post oil-change fault. I might just change a filter only to prove my poor theory attempt. If not, then replace the oil without a filter change and see how that goes.

1WILLY1

iTrader: (9)

i bought mine in the winter and hesitation didnt start until the summer months, usually when ti was very hot

Having the valve spring recall fixed the issue and it never returned

I also had spark plugs replaced so not sure if that was a factor also