Did you notice if the "knocking" or "rattling" noise happens at a particular RPM?

On the 1ZZ-FE with VVTi - they do make a slight knocking noise as they pass a certain RPM point, which happens to coincide with a particular valve timing. Usually they just happen to be noticed when there is a change in engine load/speed were the VVT adjusts the timing in response. Since the noise doesn't seem to be present at low speed / light loads and lessens at higher throttle inputs - smells exactly like a VVT operation. Coupled with normal carbon buildup, enough miles on the engine, piston design, VVTi design, and the inherent noisy nature of the 1ZZ-FE engine design - can be quite noticeable in some engines.

There is actually a TSB on this exact issue - TSB EG009-03. Not sure if it will help - this TSB will covered under the standard powertrain warranty, outside of that period (5yr/60K miles) - it will come out of pocket.

Some have had good luck with replacing the little oil filter that is part of the VVT system. Usually not a maintenance item - there could be a chance that it is clogged with something that got loosened with the additives that have been added to the oil system. This would lead to reduced oil pressure to the solenoid that controls the VVT and might cause it to react slowly or not advance/retard the valve timing correctly.

Not so much of a timing issue - just the nature of the VVTi system. Carbon deposits, especially with 100K on the clock, could be the biggest culprit here. I get the same thing on my 2002 - 150K on it right now. Runs pretty good, except for some pinging on heavy loads - but quiet everywhere else.

Quick test - try a tank of higher octane fuel and note the noise and fuel mileage. If the rattling, knocking is quite reduced and you may even see a slight increase in fuel economy - then I would chalk this up to carbon deposits. Might be a simple case of running the engine through its rev range a couple of times on the highway - couple of WOT apps probably couldn't hurt to help clear the plugs and loosen some of the deposits.

If there is no change - then I would do some more digging - I would not rule out a VVTi issue, even if there were no DTC set. The problem happening at higher RPMs (relatively speaking) should seem to point at that as a potential issue. Could be that case where the system is not quite to the point of tripping the code.

Filter is on the front of the engine (exhaust side), closest to the #1 cylinder - filter can be cleaned, o-ring needs to be replaced, cannot be reused or it WILL leak. Definitely need a copy of the factory service manual or at the minimum, a Haynes/Chiltons repair manual - one of those tings that is hard to describe with words. Sometimes, a dealership will give you a copy of the FSM and a exploded view of components - when you purchase the o-ring - can't hurt to ask.

Exactly like you said - probably just get a CEL - the engine itself will go into a "limp" home mode, so no risk of damage there.

Hmm. Any modifications - ie, aftermarket intake/exhaust, non-OEM sparkplugs?

What kind of engine oil are you running?

Did you try and run a some premium to see if the noise goes away or changes?

Another possiblity is a leaky exhaust - actually fairly common on our generation of Corolla. Can make for some unusual, intermittent rattling.

Tensioners can cause problems at certain speeds / engine RPMs - just depends on what is wrong with them. Though the tensioners seemed to be more of an issue with the 9th gen than the 8th gen Corollas.

Disconnecting the VVT-i solenoid results in no pinging = interesting.

That means that either there is a heavy build up of carbon inside the combustion chambers (taper squish design is more prone to this, causes the cylinder to rock slightly within the bore), the VVT-i solenoid is smoked, the cam sprocket is damaged, or the ECM is getting incorrect sensor readings from any number of sensors (bad sensors or bad ECM).

Have you tried filling with premium gas and see if the noise goise away or not? If it does then I would lean toward a carbon buildup issue. Otherwise, disconnecting the solenoid would show that the car doesn't run well with a specific valve timing/overlap - that could point to many potential issues.

First, lets try and verify that carbon is not the major cause. This can done with regular or premium gas in the tank, though running with premium - you can knock off two items to check on your list at once. The 1ZZ-FE engine unique piston design helps with combustion efficiency, but also makes it much easier to foul up with carbon deposits at lower engine speeds. One quick way to burn these off is to run the engine at WOT at highway speeds.

Easiest method (highway) is to run the car at a steady 45-50MPH with O/D switched off or even in 2nd gear (4-speed automatic) of 3rd gear pulls with a standard 5-speed manual. Then punch the gas and accelerate to 60-65MPH+ (no need to go crazy, no need to risk a speeding ticket or reckless driving here), then let it coast down to 45-50MPH via engine braking. Repeat several times. This will help blow loose debris right off the tops of the pistons, and will pull enough vacuum to help clean the rings as well. Should be part of every engine break-in procedure - both of my current cars have seen this, all my cars have had this over the years and all performed well.

For the solenoid and VVT-i sprocket assembly - will need more equipment and time to address those. My suggestion is to take it to a well respected dealership and let them run the test on it for you - the amount of time and labor going into it will be worth the $85 diagnostic fee, IMO. They will be able to run test with a Toyota scanner - enabling and disabling the solenoid and sensor readings electronically and seeing how the car reacts.

As for additives, I think at this point, the engine actually sounds pretty clean - could be a case of not driving the car hard enough. Sounds kind of strange - but I've seen weirder things happen. Used to work on older GM Northstar engines, those showed similar behavior, just took them out for a couple of WOT apps - 8 out of 10 times that fixed the issue. This particular engine is also very sensitive to electrical noise - if any additional electical load was recently added, it could cause weird issues in the sensors and ECM. Poor engine/chassis grounding could also be a possibility. Also, this engine has a 10:1 compression with a very tight piston to head tolerance (taper squish) - 1ZZ-FE engine is known to be very noisy and have certain "features" like a weird stumble at 3500-4000 RPM in some cars, tapping and rattling at startup and idle, and lots of piston slap in cases of heavy carbon buildup. Lots of times, motor oil choice can minimize or aggravate this behavior. Good example is Royal Purple in the 1ZZ-FE/2ZZ-GE engine family - many have found that the engine sounds like someone poured a bunch of nuts and bolts into the engine. Can be scary sounding - but the engine oil still did its job and UOAs looked clean. I've noticed that as well - with Mobil 1 compared to Pennsoil Platinum - the Pennsoil is known to be a little thicker, engine runs well on both, but the PP quiets things down considerably (though fuel economy suffers very slightly).

What's the mileage and type/weight of oil you run on this engine?

Yeah, really doesn't sound like a carbon buildup - especially from what you already done so far. I was just hoping for a simple problem, vs something protentially gumming up the VVT-i actuator/valve. Don't worry about the "torture" runs - won't hurt any of these engines one bit - I've seen demonstration tests of Toyota engines running on a test stand 24/7 jumping from idle to redline over a one week period - exhaust header was cherry red, engine teardown shown little to no wear.

Most shops have big drums of oil that they use for oil changes, some places use retail packaged quart containers - depends on the shop. The shop closest to me uses whatever they can get their hands one - sometimes its Kedall, or Pennsoil, or Mobil, or some "mystery" brand. Shops doesn't always know in some cases. For potential sludge issues, I'd suggest either running a sythetic motor oil in there (slowly cleans the engine), or some popular additives like Lucas, Rislone, MMO, and some others. Gunk engine flush works incredibly fast - but I would worry that loosening that potential sludge or deposits all at once would be more dangerous than the sludge/deposits themselves. Some have used AutoRX with good results - though I haven't tried it myself, so I can't really comment on it.

I also have some pics of the engine when the valvecover is off - there are some shots of the VVT-i actuator assembly in there. Don't mind the dirty looking engine - opened it up after a 14K run on snythetic oil - just wanted to see what it looked like and check clearances on the vlaves - before I changed it. Link to my photobucket site in my sig.

Nope - don't work for Toyota. Actually saw a demo at a conference for automotive tech several years ago - there were several commercial and print ads that covered similar tests. I think it was around the LS400 first come here to the states. Then more recently at a SEMA demo where they had a blown 1UZ-FE dynoing at a bit more than 850-900 WHP. They ran that on an engine dyno for 3 or 4 hours straight at redline - engine was fine afterwards.

Good question - the only load they had on it was the dyno itself was supplying. Assuming that there had to be some significant load, if not the turbos wouldn't have been boosting at all or very little (couple of PSI) - then that wouldn't have been much of a demo. As I remember, they were boosting at the time - though I didn't see all the details (what they were boosting, what the numbers were). Just the initial pull to verify the power claims, then one after the test to see where the engine was.

Nope, TPS sensor will show up with different issues. Possible you have extensive carbon deposits on the piston head / combustion chamber.

Did you pull the plugs out - give them a read? What did you use for engine flush? Usually I'll resort to that as a last ditch fix, not to diagnose an issue. As you've likely gathered from the various posts here and other forums - this particular engine is very picky about replacement parts, electrical noise, and oil quality.

What happens when you disconnect the OCV solenoid electrical connection when the engine is running - is there a marked change in idle quality?