1.8L starting rattle, knock, events

Haven't experienced this for a while now, but mostly last winter.

The worst time was when the AA were recovering my Prius to Toyota UK for the brake update and the engine sounded very rough, I tried to increase revs but no response from the accelerator and even the AA man said "Christ that don't sound good mate", after a couple of minutes the noise stopped and clouds of white smoke were coming from the exhaust.

I use the cheapest petrol I can find as it's a company car and I get reimbursed at a set rate per mile so this might have something to do with it, although I still use cheap fuel and like I say haven't had it for a while.

 

Yes, this engine, like the very similar 2009+ Corolla engine, has dual VVT-i (variable valve timing on both intake and exhaust valves).

But a malfunctioning VVT-i wouldn't cause valve noise. Although, it could be caused by malfunctioning automatic valve-lash adjusters (automatic valve-clearance adjusters).

My first suspect would be the oil (proper grade and quality, how often it's changed, was the filter changed etc.) and driving habits (easy or hard on the car when being driven cold). Of course, there could always be a manufacturing defect.

 

My explanation for your ignition-timing curve is as follows:

First of all, I think your RPM curve is incorrect. I would think it would start around 2000 - 3000 RPM and then it would come down to 800 - 900 RPM or so after the warm-up.

Anyway, this is the explanation:

First you see a more advanced timing because this helps engine start. Also the RPM is higher when the engine first starts; so, this is OK.

Then, after the engine started, they slowly decrease the timing advance, which helps reduce the NOx emissions. RPM is also decreasing; so, it makes sense to decrease the timing. Since EGR, the main suppressor of NOx emissions, is not on with a cold engine (it would stall it), the emission regulations would prohibit very advanced timing with a cold engine.

Then, after the coolant temperature reaches about 120 F or so, the EGR turns on. At this time it's safe to advanced the timing without increasing the NOx emissions.

I see that they fine-tune the timing a little bit more when the coolant reaches the normal operating temperature. It's hard to say why given the information. It could have to be that it's safer to advance the timing even more when all engine systems are operating normally. Not sure if the EGR flow rate is coolant-temperature dependent, but this could be a reason (higher EGR flow, more timing). Of course, EGR is only on when driving, not at idle, but they would probably assume that you could start driving at any moment.

By the way, I did own a 2009 Corolla, which has a very similar engine (other than lower compression ratio in the Corolla and the Otto vs. the Atkinson cycle in the Prius) and didn't have any problems. Of course, I always changed the oil myself with Mobil 1 0W-20, and I knew nothing was being done wrong.

I wonder if there is a problem with the automatic valve-lash adjusters (automatic valve-clearance adjusters) on these engines. Too much clearance would result in valve noise. Too little clearance results in lower performance and fuel economy as well as more engine wear. But my first suspect would be the oil change. These 0W- and 5W- oils don't have much protective film for cold-engine starts. I use 15W-40 on my 85 Corolla. In fact, 5W-30 is not recommended by Toyota for my car (and most Japanese cars prior to 1995 or so), unless at frigid temperatures, probably because they lack the protective film for cold starts. But, of course, you shouldn't use such high grades on the Prius and you should stick with what is recommended, as it would decrease the fuel mileage and could be not compatible with the new-engine clearances. Note that oil thins over time when it keeps mixing with some gasoline and hydrocarbons over the oil-change interval and this could be another reason for this valve noise.

By the way I hated the 2009 Corolla and sold it a few weeks ago. The steering, on which there are hundreds of complaints to NHTSA, was horrible. I'm very happy that I sold that car.

How often do you change your oil and what brand/viscosity do you use? Where do you have it done?

 

By the way I'm likely wrong on this one. I forgot that the Prius engine charges the battery even when you're in neutral. So, a constant engine speed around 1300 RPM throughout the temperature range might be correct because the engine is actually put under load (throttle is not at idle).

But the rest of my argument is still unchanged. Note that EGR would be on (after the coolant temperatures reaches above 120 F) even when you're in neutral because the engine is under load and the throttle is slightly open. Normally, with a conventional engine, EGR is off at idle when the throttle opening is minimal.

Again, my main argument still remains the same.

 

Yes, I corrected myself about the RPM but you didn't get a chance to read it before you replied to my post. I had forgot that the engine is always under load in the Prius. The rest of my argument remains unchanged though. As I said, the curious behavior you're seeing is very likely due to EGR off/on.

Again, this is some valve noise and and it's unlikely related to timing. I'm not sure how good quality is the "Toyota-" brand oil they use at the dealers. (Toyota doesn't make motor oil; so, it could be canola oil for what you know. LOL) I use Mobil 1 for the 0W-20 grade. And, yes, I've also heard horror stories about Toyota dealers messing up simple oil changes and causing expensive engine damage. But changing the oil yourself in no ways invalidates the warranty or decreases the resale value -- this would be strictly against the law. I had no problem selling my 2009 Corolla to the Toyota dealer even I did five oil changes on it (same oil grade, same cartridge-type filter as with the Prius) -- no questions were asked. There could always be a design or manufacturing defect with the valve-lash adjusters. Hopefully the problem is very minor and it doesn't get worse over time. If it does, Toyota would have to replace your valve-lash adjusters or make other necessary repairs. Occasional or minor valve noise wouldn't affect your engine durability otherwise.

 

There was a TSB about a cam on the VVT-i being replaced under warranty for a sound which might have been similar to this, but I don't know more about it. I'm sure y'all have already discussed it. In any case, that's a big clue, right there, that something was not quite right with the VVT-i and Toyota knows about it.

I'd think the thinner oil would be better on start up, because it would be less viscous and get to the top of the engine more quickly.

Someone mentioned white smoke coming out of the tailpipe. In the old days, black smoke=improper air/fuel mixture, blue smoke=oil getting into the combustion chamber and being burned, and white smoke=coolant entering the combustion chamber. But I don't see how that's true in this case.

I do think the VVT-i could cause this noise.

Certainly something in the valvetrain.

I do not think this has anything to do with ignition timing.

As far as the valvetrain goes, either oil is not getting to it, the oil is not providing adequate lubrication (unlikely) or something is moving through a range of adjustment, perhaps beyond, when it shouldn't and is causing noise. I really think it's the VVT-i system malfunctioning.

Anyone know the schematic on the VVT-i system on this engine? Figure out how exactly it works and how it can malfunction. I think your answer is there.

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Here's the link to the discussion:
http://priuschat.com/forums/gen-iii...nocking-noise-startup-there-may-hope-yet.html

 

Just because you're a girl, I will post these. These are for the 2009+ Corolla 2ZR-FE engine. The 2010+ Prius 2ZR-FXE engine is virtually identical, except for mainly different specs (such as higher compression) and valve timing (Atkinson instead of Otto cycle):

Part 1 (overview, details on valve-lash adjusters)
Part 2
Part 3 (VVT-i details)

The most likely candidate for the valve noise is the hydraulic valve-lash adjusters, whose main purpose is to decrease the valve noise. Note that they require oil to be circulating to function; therefore, it wouldn't be abnormal for them not to function until the oil-pressure builds up to a certain value after the cold start.

By the way, after reading the TSB on the 2ZR-FE engine, it's suggesting that the problem is due to a design defect in the intake-camshaft gear, which has now been revised. In that case it seems to be a very minor problem. If that's a major concern for you, you might want to have your intake-camshaft gear replaced before the warranty expires, but this involves people opening and poking into your engine -- so, it's a tough call.

Such design defects are usually corrected after a model year or two after the initial major redesign, and it may not be a bad idea to wait for a model year or two if you can before you jump into purchasing a major redesign.

 

Thank you.

They are indeed hydraulic lash adjusters, and I agree, that's probably where the noise is coming from. At least in that area somewhere.

Best case: It's definitely taking too long for the oil to get to the valve lash adjusters. And we're already using oil that's not very viscous when cold.

But...

—Say that, when the engine starts, the camshaft timing is doing something it shouldn't, due to a fault in the system.

—What would cause this? A faulty camshaft position sensor or valve timing oil control valve.

—Maybe it's possible that the valves are opening way too early, or too late. Who knows what that does to valvetrain clearances, as the valves attempt to open against pressures they're not designed for in the exhaust cycle.

—Maybe this results in a ton of slop, or maybe the lifters compress fully. Either one would cause significant noise.

Not saying it is the answer, just saying it might be.

I still think it's an issue with the VVT-i, especially in light of that Toyota TSB.

And, again, in the linked video: The noise is bad on start up, GETS WORSE after about 10 seconds, then gets better. If oil pressure is coming up gradually and it's only an issue with the lash adjusters pumping up, the noise would not get worse like that.

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My SC430 has VVT-i, too, twice as much going on internally, and is quiet as a churchmouse on startup. I never hear the adjusters clattering while oil pressure comes up; this situation is definitely abnormal, in my opinion. Noise=wear, and it's never a good thing to hear.

 

It would be very interesting if you could include it in your plot. I'm guessing the ignition-timing advance jumps when the EGR kicks in.

 

You're welcome Pinto Girl! We both agree that this is coming somewhere from the valvetrain and it's not engine knock or ping. According to Toyota the problem is apparently a design defect in the intake-camshaft gear in the 2ZR-FE-series engines.

 

The automatic choke in my 1985 Corolla handles starting and drivability during warm-up excellently in all temperatures.

 

A ha! I was guessing on the exhaust side, but close enough for me. Thanks again for all the info. Fun playing the 'what if' game.

Yeh, same with my '73 Pinto. Press accelerator pedal to floor and release. Turn key. Auto choke closed, high idle. Coolant temp increases, choke opens a bit, idle drops and the thing is running like a sewing machine (albeit one that might burst into flames with the slightest impact).

 

Bob, this is not what exhaust-gas recirculation (EGR) does. Again, I'd like to quote from my 1985 Corolla repair manual:

"To reduce NOx emissions, part of the exhaust gases is recirculated through the EGR valve to the intake manifold to lower the maximum combustion temperature."

Exhaust gases are cooler than the combustion chamber and they are used to cool the combustion chamber. Note that the reason exhaust gases are used instead of air is simply because exhaust gases are inert and they don't alter the air - fuel ratio. If you disconnected the EGR, your engine would start pinging (sound like firecrackers). That's because your combustion-chamber temperatures would be too high and it would result in detonation. In order to stop this (such as when EGR valve is not functioning because it's heavily clogged with carbon deposits), your engine would have to retard the ignition timing or make the air - fuel ratio richer, resulting in less engine power and less fuel economy. Although, too much EGR also results in less power and fuel economy. That's why the Toyota engines ping a little under high loads, to obtain the maximum performance and fuel economy.

EGR stays off until after 122 F and comes on before 154 F. It's off at light loads, always on at heavy loads, and modulated according to the exhaust pressure (high pressure = on, low pressure = off) at intermediate loads.

Again, the purpose of the EGR is to decrease the combustion temperature. This reduces pinging (small detonations) and NOx emissions. Because, detonation is caused by high combustion temperatures and/or low-octane gas.