A stuck controller pin (aka locked actuator at startup) is commonly misdiagnosed as a "dry start". In a way, it is. Because the vvt-i system relies on hydraulic oil pressure to function. Oil flows through a series of small channels from the pump to the actuator. Pressure is controlled by the oil control valve (OCV). Oil too thick or a blockage somewhere will delay oil flow, delay the unlocking of the controller. Thinner oil flows faster, less chance of that happening. Use of synthetic oil helps prevent deposits in the tiny passages of the vvt-i which can make the controller stick, another source of the problem. Lastly, controllers and OCV can go bad just like anything else mechanical. Fairly common for engines equipped with vvt-i to experience this issue. Take the cheapest steps first which is thinner oil, perhaps a varnish/deposit cleanup additive. 0w in a 40 is different than a 0w in a 20 depending on the air temps when the engine is started, but thats another discussion. Using a high efficiency filter with a heavy weight oil will cause a delay, its a balancing act there.
This is a hard one because of the oil used. My first thought is thickness and deposits are not causing this if M1 0w40 has been used for extended periods. And that something mechanical is breaking down. Exposed by a combination of variables discussed prior (deposits, oil thickness, filter efficiency). The best way to figure this out is a process of elimination. You put a lower efficiency filter on with better flow, went away. You got rid of the noise at the expense of filtration. What else could it be short of a faulty controller or OCV?
No engine is immuned from deposits and varnish over time. Some say varnish is harmless. I disagree. Any small oil galley like the vvt-i system or the piston oil return holes can clog with varnish, hampering flow. Switching oil brands may be useful here. Pennzoil Ultra 5w30 is what I would try. Top of the line, good in the heat, high cleaner, has PAO (according to knowledgeable chemists). Not that its better, I think a change in chemistry may do some good every so often. Clean up what another leaves behind. Using the high efficiency filter for verification it worked. May take a few thousand miles to see results.
Some don't believe in additives, think motor oil can do it all. For the most part yes, but there are times where a cleaning additive may be helpful. This is one of those times because replacement costs of a controller are high. I try everything. Kreen and Lubegard Engine Flush are what I recommend. I have cleaned stuck controllers on 2 Toyotas including the old Camry I'm driving with them. Kreen is the one that was most effective. Same as above, using the high efficiency filter for verification it worked. Should see results almost right away with these.
If a different oil or an engine cleaner don't do the trick, next would be replacing the OCV. Then finally a new controller, the most expensive of all.
Agree... If you've been following this saga you know that I just recently changed my oil filter (from a Mobil 1) to a Toyota oil filter, thinking the ADBV on the Mobil 1 filter was faulty, thus the reason for the random dry starts. Well, I thought I found the fix for the dry starts (or so I thought)...for a while until out-of-the-blue the noise decided to make itself known again - much to my surprise! (I was totally wrong in blaming the Mobil 1 oil filter...
So, I thought to myself - okay, I've changed the oil filter (which I thought was the problem) so now I'll change the oil I've always used (from Mobil 1 0W-40) to something much lighter and see if that corrects the random dry starts. Even though my oil (and oil filter) was just changed (less than 1,000 miles ago) I have now changed the [new 0W-40] oil only and replaced it with 2 qts 0W-20, 2 qts 0W-30 & 1 qt 0W-40 (which equates to a 0W-28 blend). So now I have a brand new non-restrictive Toyota oil filter and 5 new quarts of 0W-28 [blended] Mobil 1 full synthetic oil. And I still get the totally random start-up noise after the engine has been shut down for 6+ hours (whenever it decides to do it, which is totally unpredictable)...
It is clearly not the fault of the [Mobil 1] oil filter's anti-drain back valve, which I originally thought was the problem. And it is clearly not the fault of the weight or type of oil I have been using...
This all led me to further research this noise problem. I lucked into a multi-hundred post thread on a Lexus message board
that described my random start-up noise perfectly. And some of the members there had even made sound clips and videos of their noise, which perfectly matched what I was hearing from my own engine. From reading their discussions (all 965 posts!!!) and their results of taking their cars to dealerships throughout the U.S. (and the world) I was able to learn (with almost 100% certainty) exactly what my problem is - a problem with the VVT-i system.
Your explanation of the VVT-i problem is correct, but all indications are - Toyota/Lexus has never found a solution to permanently fix the problem even though they revised their TSIB five times over the years. As the link I provided (above) clearly shows, owners with this VVT-i start-up noise problem have had their cars worked on (per the various TSIBs both under warranty and out of warranty) and the problem seems to always come back. That's bad!!! It pissed a lot of Lexus owners off big-time...and I don't blame them... But where are the Toyota owners (like me) that have no-doubt also experienced this same start-up noise problem.
The cold start-up 'dry start' noise is so random, so intermittent, so unpredictable, that you can never predict when it will occur. But when it does happen it always happens after the engine has been shut down a number of hours, which allows the oil to drain-off from the VVT-i actuator 'if' the locking pin hasn't performed correctly, which all happens so unpredictably that you would rarely guess when it will happen.
I am very surprised that other Toyota V6 owners (with VVT-i systems) like myself have not complained about this cold start-up 'dry-start' noise. I cannot find any Toyota TSBs or any clearcut discussions indicating that other Toyota owners experienced this problem. This is puzzling to me. Could it be that Lexus owners are less tolerant of this sort of thing and complain more than Toyota owners? I certainly would not think so! The whole thing is very strange...