Devh

Form the very beginning of this thread hesitation on acceleration started out at one set of symptoms possibility related to the transmission and then it branched off into other areas of concern that are probably unrelated.

As I have always stated there are many causes for this condition. There is a lot of speculation and anecdotal fixes.

1. Fuel quality
2. Valve recall
3. ECU programming
4. Oil change
5. Transmission programming
6. Traction issue.

If someone blindly thinks that replacing the transmission gasket is the fix and finds out it isn't then they just wasted their money.

There are many isolated issues that have little or nothing to do with another cause, however we can do some deduction based on specific history as in the case of the infamous hesitation after an oil change which I believe is real.

texas008

I had good luck improving the throttle response by using Techron fuel injector cleaner.
worth a try.

Trumpanche

I passed 4k since my last oil change last week. Recall that I used Penzoil Ultra Platinum 0W20 for that one and then have been having intermittent hesitation ever since - pretty much like the previous two oil changes. (and just for the 'fuel' guys - I have only used Chevron premium fuel for the last 15k mi)

Well, for the past week, without exception, the "light bulb" switched on and the car drives perfectly (sort of in the way Road Frog describes - it's not just OK it's like flawless... perfection - super smooth off idle and all the upshifts and the downshifts just when and how you want them.).

An interesting coincidence is that the oil level warning light popped on for a brief second when I was parked on a steep sideways slope late last week and then quickly went off again. I verified when I got home that the engine is definitely consuming oil (it was on the high side between the two dots on the dipstick after the oil change and is now just below the 'low' dot).

This issue is completely nuts, but given that the oil level being low and the performance being good seem to be related (or coincidental) makes me ponder...

I am considering topping off the oil level again, but if it reverts to its old crappy ways I won't really know if it's the "used oil properties" or the "low oil level" that finally helped. But if the performance stays good I'll at least know that it's not the low oil quantity that's giving me the good performance.

I'd really like to take my remaining 850 miles of good performance (before my next oil change at 5k) and run with it. What would you do in my position??

NickTee

Or we can deduce that people are reading this thread and are experiencing the placebo effect after the oil change, when the problem may have already existed in the first place.

Trumpanche

Well I put my big boy pants on and topped off the oil over the weekend (around 2 qts). Still runs great, so oil level seems to not have been a factor. I'm hoping DevH is right and this oil just took a while to get all the engine internals spic-and-span.

NickTee

Considering the areas lubricated by oil, it does not make sense that it would clean up anything that would cause hesitation unless there was a huge amount of buildup on the piston walls that was allowing excess gasses to enter the crankcase(blow by). Another possibility that comes to mind is that there was an issue with the PCV system and the oil level/pressure caused by the oil being used was causing excess oil to enter the intake manifold through the PCV system and causing hesitation. That or it was blocked and had nowhere to go.

Just a hypothesis.

Devh

It is most likely the VVT oil control valve strainers as I have discussed before in previous posts with links to other forms where this is an issue with other newer Toyota engines. The varnish deposits find their way through the oil and get trapped at the strainers. This causes a lack of flow which interrupts the operation of the VVT because its oil pressure dependent. After some time the cleaning action of the oil liquefies the deposits and the hesitation goes away. This cycle will continue and will eventually subside once the engine is free of deposits. The initial cleaning of synthetic oil is the harshest after an oil change. Some cars that run conventional oil have developed deposits after many miles have to be pulled and serviced where as the dealer Will replace the part at the owners expense when it doesn't need to be.

superdenso

I would get the procedures for a drain refill and get under there.

Check for Trans for leaks from seals around the pan. If you don't see any-> drain and refill the Trans. It's a slightly complex procedure but achieving the correct level is very precise and easily obtained. (Level 6 difficulty).

NickTee

You can always take it apart and check the strainers and oil control valve, since the most effective way to clean the valve strainers is to replace them, just like the only way to clean carbon deposits from an engine is to actually take it apart, soak the carbon, and wipe/scrape it off. The symptoms reported don't seem to coincide with the symptoms of clogged VVT strainers.

If you want to see some delicious clogging, look here(not the same engine, but still the same concept execution):
http://au.toyotaownersclub.com/forum...tersstrainers/

Devh

Yes that is the way to do it right however It depends on the accessibility of the actuators and the bolt. On some cars owners have removed the actuators, cleaned the strainers and it has solved the issue especially when it gets so bad that it throws a check engine light. But unfortunately as an owner of both of those engines 1zz and the 2zz actuator access is nearly impossible without dropping the motor.
What they found out is that those cars that ran synthetic most of it's life did not have clogged strainers.
It would be great if one of our members went though the process of locating the actuator and checking to see the condition of the strainer.

robert1408

Alldata shows a cam timing oil control assembly for each exhaust cam at $125 each. Warranty labor time to replace them is .8 for one and 1.0 for both. They are bolted on top each valve cover on the exhaust side, at the front. Remove the engine cover and enough air filter stuff for access.

No mention is made of a screen or strainer, but there is bound to be one in the inlet port of that valve. This is a common design and the screen sometimes is removable, sometimes not depending on the car.

Alldata does mention testing the function of the valve using Techstrean to command the valve on either bank while at idle. The idle gets rough if the valve is working.

I suggest for anyone interested in working on these cars to get an on-line subscription to alldata. It's only about $30/yr. It is not as extensive or detailed as a factory manual but it's still a mountain of information about these cars. The search feature works very well. It had labor times and approximate parts prices. Highly recommended.

Trumpanche

Driving home from work on a hot afternoon. I sat through three light cycles at a congested intersection and then experienced a severe hesitation episode (the classic symptom of flooring the throttle, the rpms raise slowly but surely but no torque behind it). The hesitation cleared up after about a mile of normal driving after that. The engine was perfect the rest of the evening. I suppose it could be related to either the low oil flow rates at idle, heat soak in the fuel, or heat soak on a sensor... but I'm still at a loss.

Trumpanche

I'm not saying it's necessarily the two quarts that I added, but I've experienced hesitations and good performance intermittently for the last few weeks. Oil change with the Toyota oil this week so we'll see how that goes. I don't have my hopes up.

jfattibe

Its been 400 miles since I did my oil change and I'm experiencing the same thing. One day it was hesitating so bad I took it on the highway and let it shift out twice at 6000 rpm. When I came off the highway it was fine. A couple of days later the bride and I took a day trip to Plymouth MA. Stop and go traffic and lots of idling. Needless to say on the way home the hesitation returned. The next day on the way to work, another 6000rpm blast onto the highway and its been ok since ???? One question..Does anyone know why it smells like rotten eggs after a good rev ?? Is there something messing with O2 sensors ?? cause thats the only thing that comes to mind with that smell.

Doublebase

You could be dumping some raw fuel on the cats after such a high rev, when it burns off it sometimes can smell like sulfur.