NEW!!! Service Bulletin for Engine Knocking at Startup T-SB 0012-10

It doesn't have to be a safety issue only, this is for defects as well, which this obviously is. We also don't know the long term effects of this problem, it could be a safety issue later on, like the car just cutting off in the middle of the road or something.

 

Also, I need to make a correction on the web sites, it's safercar.gov not safecar.gov.

 

Also, I need to make a correction on the web sites, it's safercar.gov not safecar.gov.

 

Hi Guys & Gals,

Please excuse my lack of effort on this, but I've read the first few pages and the last few of the 32 already in this thread, and didn't see any real answers to this problem. It sounds like no one really knows how to address this? Is there anyone who can explain what is happening here? Also, is this problem only occurring on North American Gen3 models, or is it more universal?

From what I have gleaned here and there, my understanding is that it's caused by water condensation forming in the EGR pipe / valve during cold weather?

Next morning, when starting the ICE after a cold soak (e.g. overnight) following an interrupted ICE warm up cycle the previous day, this water is sucked into the Intake Manifold, and, prior to fitting the modified Intake Manifold, usually ends up going straight into the first cylinder to "draw breath" that day. There, it gets splattered all over the spark plug, shorting it out temporarily. (This could presumably happen on more than one cylinder and probably cause even more pronounced effects.)

Anyway, with one spark plug temporarily out of action, the engine will be running very roughly "on 3 cylinders". (It will come right after running a while due to the combined effects of airflow through the cylinder and the heat of compression drying the spark plug out, and this is reported in various posts and videos.)

Obviously, the knocking noise is not a sign of a happy engine / transmission.

I have developed a detailed theory of what is going on here and already have an understanding of why the knocking noise is produced and is so pronounced, but before I bore everyone with the details, may I ask a simple question.

One poster in this thread (can't find it now...) has advised that flooring the gas pedal when the knocking starts stops the knocking.

Has anyone ever tried immediately placing the Transmission into Neutral? I believe that should make a significant difference. May not stop it completely, but from what I understand, it should make a big difference.

Has anyone tried that?

 

Hello Al. There have been many a theory presented here. There was a certified Toy mechanic here that explained it with pictures either in this thread or another. I think his handle was Kory or Cory.
Anyway, IIRC:
The original IM interior was designed smooth. Condensation would puddle within the manifold. When started, the water would be sucked into the cylinders causing the misfiring. Someone else suggesting the banging was magnified by the friction plates in the trans-axle.
As a fix, Toyota issued the TSB that replaces the IM with one that has ridges to hold the puddled water at least for a moment. There have been four versions of the IM since.
The IM is made of a composite material and not metal/alloy as the previous generations had. This might have something to do with it. My theory. With that said, out 11 Rolla has the same IM and it has not done this.
I am sure others will chime in with their version.

[edit]
The member is Kore971
Here is the damper explanation: 1.8L starting rattle, knock, events | Page 20 | PriusChat
I think that is the thread that contains the IM pictures.

 

Hi there spiderman,

Thanks for your reply!

Whew, another very long thread! Didn't find the pictures yet, but never mind. To my way of thinking, the Intake Manifold is not the source of the problem, so it's not the right place to attempt a fix. Apologies to Toyota, but it seems more like the ambulance at the bottom of the cliff.

Anyway, it's summer down here, and it's clearly a pretty cold winter in the Northern Hemisphere, so a lot of you Northern fellow Prius owners are either having, or anticipating this problem. Seems like a good time to look into it more?

Problem is, I don't have a Gen3, only a Gen2, so can't try any of these things for myself. But I love a technical mystery / challenge. If anyone is keen to try a few things for me, maybe some answers can be worked out? (I believe that one doesn't have to be a Toyota Engineer to solve this!)

I don't know if the HSD system on the Gen3 operates the same as the Gen2 does, but I believe certain things will be the same. In particular, I think the operation of the Neutral "position" (mode/status) of the Transmission should work much the same.

On my Gen2, when I cold start the ICE, I notice that the engine sound and behaviour changes noticeably when shifted from Park to Neutral (during the first few seconds in particular). There are a number of reasons for this which I can elaborate on later if it turns out to be relevant.

If any of you Gen3 owners are interested in solving the Cold Start Knocking issue, would you mind doing a small test for me please?

Next time you cold start your beloved Gen3, would you please (with park brake on and foot on the brake pedal), try shifting the Transmission into Neutral?

Do you notice changes to the sound of the engine? My Gen2 immediately runs much more smoothly and quietly. Incidentally, the accelerator pedal also no longer does anything. Of course, if the engine starts to rev up too much, be ready to hit the Power switch to stop it, though I doubt this would happen.

Would you mind letting me know if you find similar results? Does the engine sound as if it has slowed down (or sped up), and does it sound as it it is now running under much less load? My G2 seems to slow down, and be under much less load. If that also happens to the G3, I'm willing to bet that switching a knocking engine into Neutral will stop the knocking. If it does, I believe the solution is very simple!

Anyone keen to give this a go?

 

Also, does anyone have any pictures, drawings or other info about the EGR valve and its piping and operation? I guess the EGR valve must be open when the engine is off? Is it also open when the engine cold starts? Anyone know, please?

 

I'll try it, even though my knocking noise hasn't happened again since CEL came on.

 

OK, so the Toyota Service Director calls me in regard to an email I sent Toyota when I learned about the continuity of this so called IM issue (I think that's the word I'm looking for = continuous, repeating). He's telling me about how Toyota is addressing the problem with the TSB and that it can happen to any make of vehicle with a faulty part, etc., blah, blah,. I also told him about this site and how "on the site I found a really great video about how to drive the Prius for the best gas mileage". His response was something along the lines of, "Well, on any chat site you will find lots of negative and positive topics."

Anyway, my IM is in and will have it replaced on Tuesday.

Car has been running GREAT - 600+ miles this week - 45 mpg avg w/heat, it's been sooo cold! I did hit a chunk of snow, I ought to check out that low front end piece, it made quite a racket!

Oh, btw, I'm using HEET in the gas tank when I fill up. A fellow Prius owner suggested that and I do use it in my other vehicle parked outside of the garage.

Thanks all.

 

no problem, my pleasure.

yea, I didn't either.

probably not the entire cause at a minimum and I think they know that now.

true enough.

of course, when the prius is in neutral, the HV is disconnected from the system so there is no charging load on the ICE. it is going to sound different.

I suspect this would have similar effect as pushing the accelerator pedal; it changes the RPMs of the ICE getting it past the misfiring. Just a thought.

fly-by-wire

If won't unless the system malfunctions.

 

Yes, precisely! Not only sound different, but behave differently as well. Without getting too long winded, I believe the fact that the Hybrid system is running while the engine is misfiring is the primary cause of the knocking coming from the transmission.

That's why I'm keen for some Gen3 owners to try throwing their cold engines into Neutral as soon as they start. To confirm that the HV system is also disconnected in Neutral on a Gen3. If that's the case, then the next step is to try putting them into Neutral as soon as they start knocking.

If that works, then it's a useful workaround for owners to do if knocking happens. And maybe Toyota could add a firmware change, so that when cold starting the system at temperatures below say 40F, to first start the IC engine without the HSD system engaged, and ensure that it's not misfiring before engaging the HSD. That should be pretty easy for them to do. The "Ready" light could start flashing to indicate "ICE warmup without HSD system running".

Yeah, kinda. I don't believe that's the full explanation though. I recently worked for 2 1/2 years for an Industrial Automation Supply company, and I learned a bit about servo motors, servo control systems, inertia matching and so on.

As I understand it, this problem has a couple of aspects. One is the inertia match between the misfiring ICE and the MGs. When the engine is misfiring, I suspect the inertias between the two sets of rotating masses probably hit a harmonic frequency. It's like when driving along (in a 'normal' car) at a certain engine RPM, and something inside the dash or somewhere starts to rattle. Above and below that RPM, the rattling goes away. This is an example of harmonic resonance, and I suspect this is what is happening inside the Prius Transaxle.

That's probably why pushing the accelerator stops the knocking, because the engine speed moves outside the resonant frequency range. What I'm wondering is whether taking the load off the Motor Generators by switching into Neutral will have the same effect?

If it does, great. Everyone can stop the knocking and eliminate that awful shock loading of their transmissions without needing to try revving up a cold, misfiring, unwilling, struggling engine.

Yes, fly-by-wire indeed! Glad to hear it won't rev up - I know it "shouldn't" but shouldn't and "won't" aren't quite the same!

I was just pointing out that in Neutral, you lose accelerator control, but it still works in Park, I think.

 

Hi Cjeigh,

Please keep us posted on how it goes. If you get a chance, could you get comparative photos, esp. of the differences in the new one? I know there are photos here somewhere already, but spiderman and I haven't been able to find them yet. And who knows, your new one might be different again.

Yes, aren't they SOOO MUCH FUN!!! I love mine too, despite it's annoying foibles. My wife is getting jealous!

Yeah, mind the snow!

I don't know what's really in HEET (iso-prop?), but I doubt it's going to make much difference - okay, any difference - to this "drowned spark plug misfiring" problem. Might even make it slightly worse, as wet iso-prop will be harder to light / burn in a cold engine than ordinary fuel. Being a fuel-injected system, there will be fuel filters in the system which should stop any (small quantities of) water getting through. And, with the fuel tank liner (cka Bladder) system, the chances of condensation in the fuel will be even lower. Won't stop "horizontal" rain getting in during refueling stops, of course, so occasional fuel system de-watering must be a good idea. Is HEET expensive?

 

not expensive, $2 maybe?

 

Sounds interesting... keep up the good work.

Or at best a work-around. Despite this site having quite a few members, it is still a small percentage of owners and Toyota should really put some elbow-grease into figuring this one out.

In Park you can start/rev the engine up to +-1800 rpms.

Cheers

 

In the last week I have talked with a gentleman who is an expert on gen 2's (owns a business specializing in gen 2 repairs and service and hybrid battery rebuilds) but found my gen3 video very interesting. He told me what his theory was. A couple of days later, I showed it to a gentleman here in town that has been familiar with my problem since the beginning. He also owns a automobile and transmission service business and is very involved in auto racing, so knowledgable about engines. Both, not knowing the other and on different days, said virtually the same thing: the plastic/composite material used in the IM cools much quicker than the aluminum/alloy version. The aluminum/alloy version allows for most, if not all, of the condensation to evaporate during the cool down period. No moisture, no foul. I have a neighbor who owns a regular Prius and has had the problem several times this winter. He also owns a Prius C 1.5L, which has the alloy IM, and it has never had the issue. Let's see...a redesigned alloy IM for all gen 3's would cost Toyota how much? My guess is they will fix it in the next generation of Prii and deal with us one on one. Just a thought.

 

There seems to be about 3 or 4 different threads on this problem, so it's really hard to determine where the actual problem is occurring, if it's just the 1.8L engine, certain model years, models with a particular IM, etc. It would be nice if we could somehow get these threads merged together, so we could see how many people are actually experiencing the problem.
I was able to get the TSB for the IM replacement done on my car when I took it in for the 45K service, but I'm still not convinced this will resolve the problem. From what I have read on the various threads, the problem seems to occur after starting the car and then moving it a short distance, then cutting the car off b-4 the ICE fully warms up and then not starting the car again for a while, maybe after 8 hours or more? I don't think it's related to the temp. either, as I was down in Florida when it occurred, the temp. was cooler than normal but not below 45F. I tried letting the car sit for 2 days when I got back to NC, temp. each night was below 20 F both nights, but didn't have a problem with ICE starting. The only difference was the car was in the garage (it was outside under a car port in Florida) and I didn't move the car a short distance, then cut the car off.
I didn't think I had moved it a short distance in Florida; but after I thought about it, I believe I moved it to let my dad move his car and park behind me. I didn't start the car again for 2 days and that was the first time I had the problem, like I said b-4, the whole car shoot and it sounded like the engine was going to blow up. I shut the car off and then restarted it, it may have knocked a little, but didn't rattle or shake like it did that first time. I haven't had the problem since, but I also haven't tried moving it a short distance and cut the car off before the ICE warms up, then let it sit for 1-2 days either.
I haven't tried anything since I got the TSB done, but may try the procedure to see if I can duplicate it again. I would like to know if the issue is resolved, but also don't want to push my luck with the dealer either, since they were willing to replace the IM without duplicating the problem. Has anyone else tried to create the problem after getting the IM TSB done, I think I remember a few stating that they still had the problem.

 

Hi there 1945steve,

I agree it's a great theory, and it's looking for the cause rather than a workaround, but I'm not convinced it's the complete explanation. Maybe I need to put up my theory, but thought it was too long winded.

While I agree the plastic manifold will cool much faster, and is thus more likely to attract condensation, it doesn't quite fit the rest of the facts.

It seems to be well recognised here that the most reliable way to cause the misfiring and resulting hammering inside the transmission is to interrupt the ICE warmup cycle prematurely. Say, because you just want to move the car from the driveway into the garage. So, the engine doesn't have time to even warmup, and likewise, nor does the intake manifold. About the only thing that will have time to get hot is the exhaust manifold, which seems to be made of pipe rather than cast iron. So it will cool down much quicker as well.

The other problem as I see it is this: Where is all this moisture coming from? It's certainly too much moisture to have come from just the air in the intake manifold. The answer then just HAS to be that it's coming from the exhaust system. This makes a lot of sense, because burned fuel contains a lot of water vapour. The exhaust system will be cold, and so a lot of water will condense inside the exhaust pipe, the catalytic convertor, mufflers, etc. I have seen this in many other cars - the exhaust system after a short period of idling is quite literally wet inside. Rev up the engine and liquid water will spray out the exhaust pipe. Witness the black mark left when starting up too close to a wall.

So, the question is: how does this moisture get from the exhaust system into the IM? There can only be two ways that I can see.

1. Through the EGR Valve and plumbing. Hence my questions about the EGR valve opening times.
2. Through the combustion chamber, due to valve overlap.

The 2nd option is a good contender, in my view, but we can't rule out 1 without investigation.

From experience, I know that it is highly unlikely for a normal 4 cylinder engine to stop with valve overlap. This only occurs close to top dead centre at the end of the exhaust stroke and the start of the intake stroke. However, because there is always one cylinder on the compression stroke at each TDC on a 4 cylinder engine, the compression pressure will almost always push the crankshaft forward or backward to around about 90 degrees (+/- 20 degrees). This will result in no valve overlap, so no path for wet exhaust vapour to travel to the IM - except through the EGR valve, possibly.

However, the Prius, with its modified Atkinson cycle engine may well be different. The valve overlap is probably not much different (I haven't checked), but the intake valve timing is very different. This may mean that the engine doesn't kick past TDC so well, and may mean it stops at TDC quite readily.

Or, maybe that's where the computer stops it!

Both possibilities are complete speculation at this stage, but so far, apart from the EGR valve, I don't see how that much condensation - to form a puddle big enough to soak the spark plug of one cylinder on the next start - is going to form in the IM, unless there is an open path from the EM.

If there is valve overlap, Mother Nature (chemistry) will ensure that water migrates out of the exhaust system (the driving principle of osmosis for example, also applies here), regardless of warm, hot or cold manifolds. But what is different about the Gen3 from the Gen2 that means this is a problem?

That's what puzzles me the most.

 

I'm not 100% sure, but the Gen3 models have a 1.8L engine and I believe the Gen2 had the 1.5L engine, which is probably the same one used on the Prius C that doesn't seem to have this problem. I don't know enough about engines, etc. to know the differences, but from the way the problem occurs, I have always suspected that the issue was with the computer and how it was programmed. I would think the programming would need to be different for the two engines.

 

I took mine into the dealership today with the TSB printed and a video of the car going bezerk. They said "the video is good, but we need to see it" so they kept it overnight. What a bunch of BS. Just apply the TSB and go back to making money changing oil. What the heck? It is still under factory warranty and they get paid something by Toyota. Why not just do the job and please your customer. I've bought 3 new Toyotas from this place and even told my salesman to discuss my repair with the service manager. Now I'm out of a car for 2 days. Then, if they agree to apply the fix, I have to wait till the parts come in and be without another day. Terrible customer experience...

 

Please see my new thread, "Prius Trouble" - my Prius saga continues, unfortunately : (