Working on my first VVT engine. Some questions.

M

MrPlow

Joined
Nov 22, 2020
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My Sienna van has one of the earlier VVT Toyota designs. Engine started bucking like a mad bull and tossed the p1354 code for a faulty VVT oil control valve. Luckily I limped it home before it got worse. I ordered the OEM unit for the left bank cam phaser and installed it.

One thing that seemed strange is that the RPMs went really high after installing it on a cold start. Usually it doesn't go over 2K, ever. But right after replacing the oil valve and starting the engine, it went up to 2.5K RPM. I then drove it for a week and each cold start after that was normal at about 1.5K RPM.

Today, I installed a new OEM right bank valve proactively, since they tend to go out around the same time. Once again, on the cold start after the swap, the engine raced up in RPM to nearly 2.5K. What could be causing this? Does removing a VVT control valve allow oil to drain out of the phasers, making them a bit off until the engine has run a bit? Or does the engine have to re-learn the advancing and retarding of the cam phasers once a new one is installed?

Also, curious if anyone has any ideas on why the VVT oil control valves would be more likely to be faulty in cold weather? I've read reports from others with the same engine (Toyota used it on a massive number of cars/vans/SUVs) that the engine started acting up in cold weather due to failing valves, but not in warm weather. The left bank (front) valve on this engine sits a bit exposed and probably gets a good blast of cold air when driving down the highway. Maybe the cold is just enough to cause a failing VVT valve to become extra sticky and poorly performing? The engine actually did toss a code for the left bank a little over a month ago during the previous cold snap, but went away and didn't cause the engine to run poorly in warmer weather, but then ran perfect with no codes until the next cold snap.
 
Relearn idle after battery disconnect... not VVT related

What is the maintenance history of this engine? oil types/grades/intervals used and vehicle mileage?
 
Greasymechtech said:
Relearn idle after battery disconnect... not VVT related

What is the maintenance history of this engine? oil types/grades/intervals used and vehicle mileage?
Click to expand...
Didn't pull the battery for this job since the electrical contacts for the plugs are recessed in plastic and not in much danger of touching something and shorting out. Also, engine does not do the high RPM on cold start after all the other times I had the battery pulled. Might point to oil in the phasers draining, or air getting in someplace where it needs to pump out after running for a bit?

Not sure about what was done to the van before I got it last summer, but I've been running 5w-30 semi-synth with OEM filter the last OCI.

It's a 2002 Sienna with the 3.0 V6.

If I don't learn why it did what it did, no big deal. As long as it is working is all that counts for now. But, I would like to know what others think, who have way more experience with VVT systems.

Another general question I have is why do shops charge so much for replacing the VVT control valves? I think dealerships and reputable shops can charge up to $700 for the job. I'm not even close to very good at working on vehicles and had them both swapped out in what probably combined for a total of 30 minutes. First was a 5 min job and second was around 25. Cost me $180 for the two OEM units and that was that. I wonder if shops get away with their price because when the VVT valves go bad, the engine runs so bad it feels like it is about to go completely dead and ruin itself forever. People might take it in thinking the worst (new engine) and are happy with just a $500-700 repair bill, even though the shop probably took less than an hour to swap them out. I did notice that the repair manuals call for removing way more stuff for the job than necessary. I didn't have to remove the air box or anything else, just disconnect a couple of vacuum lines and the rear one wiggled right out with no fuss. Could be the shops are basing the time on having to do all the extra work instead of doing it the smart, YouTube way. :)
 
JustinH said:
Our older Toyota Matrix would do the same thing, it is related to disconnecting the battery and relearning something.
Click to expand...
No battery disconnect, both times it ran the RPM really high for several minutes on cold start. Sure, not 100% smart doing it that way, but I made certain nothing shorted. Codes were cleared with my OBD II unit.
 
The ECU saw that it has new serials for the VVT (it communicates digitally with them) and started with the highest rpm, because that's the most conservative option to insure that the car started with the new parts. Probably at 2,500 rpm, the advance/delay of timing is zero, so even if the parts were not working, the car would still work with proper timing.

After that it re-learned the new VVT behaviour.

Just for curiosity, this is the diagram from my RAV4:
VVT.png
 
MrPlow said:
If I don't learn why it did what it did, no big deal.
Click to expand...
An informative experiment would be to remove and replace the new valve and see if it reproduces the high idle.
That will show if the computer was compensating for the old valve.
 
SoNic67 said:
The ECU saw that it has new serials for the VVT (it communicates digitally with them) and started with the highest rpm, because that's the most conservative option to insure that the car started with the new parts. Probably at 2,500 rpm, the advance/delay of timing is zero, so even if the parts were not working, the car would still work with proper timing.

After that it re-learned the new VVT behaviour.

Just for curiosity, this is the diagram from my RAV4:
View attachment 47436
Click to expand...
Very interesting! Thanks for posting. The control valves are looking to be a lot more complex and precise than I had thought, which might explain why they can appear to be functional when bench testing, but still fail in use since they are not working just perfect enough for the ECU. Which could also explain why so many of the aftermarket ones don't work or fail so soon. Glad I went OEM for these, and it appears Toyota redesigned the valve units at some point, as the new ones look much more robust than the originals.
 
circuitsmith said:
An informative experiment would be to remove and replace the new valve and see if it reproduces the high idle.
That will show if the computer was compensating for the old valve.
Click to expand...
Maybe, but I am not going to do that for several reasons. First I don't want to disturb the new valves after being put into place, and I only have the right bank old valve on hand (other got trashed and was not working). Second, it wouldn't remove the possibility that taking out the valve somehow allows oil or air to drain or move inside the phasers or other associated parts.

I think SoNic posted above might be the correct answer to what I was seeing. I might have also noticed on my test drives that it took a couple of miles before the engine had full power. Felt a little pulled back, which might have been the ECU playing it safe until it could get the cam angle sensors where it wanted them with the new valves. Makes sense seeing as how the engine can misfire really bad without proper phasing of the cams.
 
I would also like to give a shout-out to Conicelli Toyota for excellent prices and service for OEM parts. Been buying from them for a while and they are always coming out with the best online prices for genuine OEM and they ship really fast with good packaging. I usually purchase through their Amazon storefront, but they also sell directly. https://parts.conicellitoyotaofconshohocken.com/
 
Most of the time the ecu has no idea that its off, when it detects this from the vc line, the degrees then it will start adaptation. Its the reason why this happens. You are lucky that its just plug and play unlike german cars we have to reprogram everything with vcds
 
since you mention 'COLD' 6-8 times in OP please put a general location in your signature. geez.
 
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